JP2000277158A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance energy density by preventing a mixture layer from being retained on the electrode surface not facing to the opposite electrode plate to be faced interposing a separator on an electrode plate used as the outermost circumferential part. SOLUTION: In this battery, an elliptical rolled power generation element comprising a positive electrode plate, a separator and a negative electrode plate is received along with an electrolyte in a bag-like cell case formed by thermally welding a metal laminated resin film. The rolling center axis of the elliptical rolled power generation element is preferably perpendicular to the opening face of the bag-like cell case. In a negative electrode base material 11 that is an electrode plate located on the outermost circumference of the elliptical rolled power generation element, a negative electrode mixture layer 11 is not retained on its outermost circumferential part not facing to a positive electrode base material 10. Therefore, the thickness of the battery can be reduced by a portion equivalent to the negative electrode mixture layer 11, so that energy density can further be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery in which a power generating element is housed in a bag-shaped unit cell case.

[0002]

2. Description of the Related Art In recent years, electronic devices such as a portable radio telephone, a portable personal computer, and a portable video camera have been developed, and various electronic devices have been reduced in size to be portable. Along with this, a battery having a high energy density and a light weight is also adopted as a built-in battery. A typical battery that satisfies such a requirement is an active material such as lithium metal or lithium alloy, or a host material containing lithium ions (here, a host material refers to a material that can occlude and release lithium ions). Lithium intercalation compound occluded in a certain carbon is used as a negative electrode material, and LiC
This is a non-aqueous electrolyte secondary battery using an aprotic organic solvent in which an electrolyte salt such as l04 and LiPF6 is dissolved as an electrolyte.

This non-aqueous electrolyte secondary battery has a negative electrode plate in which the above-mentioned negative electrode material is held on a negative electrode current collector as a support, and a reversible electrochemical reaction with lithium ions such as a lithium-cobalt composite oxide. The positive electrode plate, which holds the positive electrode active material that reacts on the positive electrode current collector that is the support, from the separator that holds the electrolytic solution and intervenes between the negative electrode plate and the positive electrode plate to prevent a short circuit between the two electrodes Has become.

[0004] Each of the positive electrode plate and the negative electrode plate is formed into a thin sheet or foil shape, and is a power generating element formed by sequentially laminating or spirally winding through a separator. Then, the power generating element is housed in a battery container made of a metal such as stainless steel, nickel-plated iron, or aluminum, and after injecting the electrolytic solution, hermetically sealed with a lid plate to assemble the battery.

However, when a metal battery container is used,
Although it is highly airtight and has excellent mechanical strength,
There are great restrictions on battery weight, battery container material and design.

In order to solve the problem, a method has been proposed in which a power generating element is housed in a bag-shaped unit cell case.
In particular, by using a metal laminated resin film having an airtight structure as a material of the bag-shaped unit cell case,
There is no leakage of electrolyte or intrusion of moisture or the like from the outside of the battery, and the battery can be reduced in weight.

[0007] The shape of the power generating element is a wound type,
In particular, when the cross section is non-circular or oval, the electrode surface area can be increased and the manufacturing process can be simplified.

When such a non-aqueous electrolyte secondary battery is used in electronic equipment, a predetermined voltage is obtained as a unit cell or a plurality of cells connected in series. The single or plural batteries are housed in a housing made of resin or metal and resin together with the charge / discharge control circuit, and sealed so that the contents cannot be taken out, and used as a battery pack.

[0009]

When a positive electrode plate and a negative electrode plate each having a mixture applied to the positive and negative electrode base materials are spirally wound through a separator, the positive electrode or the negative electrode plate is disposed at the outermost peripheral portion. When an active material that does not face the negative electrode is present, there is a problem that the battery thickness increases by the thickness of the mixture layer and the energy density decreases.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a non-aqueous electrolyte battery having a high energy density.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an oval wound type power generating element having a positive electrode plate, an isolator, and a negative electrode plate housed in a bag-shaped unit cell case. In the nonaqueous electrolyte secondary battery, the electrode plate corresponding to the outermost peripheral portion of the elliptical power generation element does not hold the mixture layer on the electrode surface not facing the counter electrode plate facing the separator. And

Further, the present invention is characterized in that the electrode plate corresponding to the outermost periphery of the elliptical winding type power generating element is a negative electrode plate.

Further, according to the present invention, the bag-shaped unit cell case has an airtight structure, and the oval wound type power generating element is housed such that the winding center axis is perpendicular to the opening surface of the bag-shaped unit cell case. It is characterized by having been done.

Further, the present invention is characterized in that the material of the bag-shaped unit cell case is a metal laminated resin film.

[0015]

Embodiments of the present invention will be described with reference to the drawings. The external appearance of the nonaqueous electrolyte secondary battery according to the present invention is shown in FIG. 2, and the winding center axis of the elliptical winding type power generating element is perpendicular to the opening surface of the bag-shaped unit cell case. And stored in a bag-shaped unit cell case. FIG.
In the figures, 1 is a bag-shaped unit cell case, 2 is a power generating element, 3 is a winding center axis of the power generating element, 4 is a positive electrode lead terminal, and 5 is a negative electrode lead terminal.

FIG. 1 shows a cross section perpendicular to the center axis of the winding of a non-aqueous electrolyte secondary battery according to the present invention. In FIG. 1, 4 is a positive electrode lead terminal, 5 is a negative electrode lead terminal, 9 is a positive electrode mixture layer, 10 is a positive electrode substrate, 11 is a negative electrode mixture layer, 12 is a negative electrode substrate, and 13 separator. In the nonaqueous electrolyte secondary battery according to the present invention, as shown in FIG. 1, an electrode plate corresponding to the outermost peripheral portion of the elliptical power generating element, and an electrode surface not facing the counter electrode plate facing the separator. Characterized in that the mixture layer does not hold.

In the present invention, when the elliptical wound type power generating element is housed in the bag-shaped unit cell case, the winding center axis of the oval wound type power generating element is set at the opening surface of the bag-shaped unit cell case. Preferably it is vertical. The vertical direction is
It does not only mean completely vertical, but also generally vertical.

In the present invention, a metal laminated resin film is used as the material of the bag-shaped unit cell case.

As the material of the metal of the metal laminated resin film, aluminum, aluminum alloy, titanium foil and the like can be used.

As the material of the heat-welded portion of the metal laminate resin film, any material may be used as long as it is a thermoplastic polymer material such as polyethylene or polypropylene.

Further, the resin layer and the metal foil layer of the metal laminated resin film are not limited to one layer each, but may be two or more layers.

Examples of the bag-shaped unit cell case include a laminated case formed into an envelope by heat-welding a metal-laminated resin film, a case in which four sides of two metal-laminated resin sheets are heat-sealed, and a single case. Use a metal-laminated resin film case of any shape, such as one obtained by folding the sheet in two and heat-welding the three sides, or a laminating case in which a power-generating element is placed in a cup-shaped metal-laminated resin sheet. be able to.

As the solvent of the electrolytic solution used in the nonaqueous electrolyte secondary battery according to the present invention, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethyl Acetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran,
A polar solvent such as 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a mixture thereof may be used.

The electrolyte salt dissolved in an organic solvent includes LiPF6, LiClO4, LiBF4, LiAsF.
6, LiCF3CO2, LiCF3SO3, LiN (S
O2CF3) 2, LiN (SO2CF2CF3) 2, L
iN (COCF3) 2 and LiN (COCF2CF
3) A salt such as 2 or a mixture thereof may be used.

The separator of the non-aqueous electrolyte secondary battery according to the present invention may be an insulating polyethylene microporous membrane impregnated with an electrolyte, a solid polymer electrolyte, or a solid polymer electrolyte. A gel electrolyte or the like may be used. Further, an insulating microporous film and a solid polymer electrolyte may be used in combination. Further, when a porous solid polymer electrolyte membrane is used as the solid polymer electrolyte, the electrolyte contained in the polymer and the electrolyte contained in the pores may be different.

Further, as a compound capable of inserting and extracting lithium as a positive electrode material, an inorganic compound is represented by a composition formula L
ixMO2 or LiyM2O4 (where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2), a composite oxide, an oxide having tunnel-like vacancies, or a metal chalcogenide having a layered structure is used. be able to. Specific examples thereof include LiCoO2, LiNiO2, and LiMn2O.
4, Li2Mn2O4, MnO2, FeO2, V2O
5, V6O13, TiO2, TiS2 and the like.
Examples of the organic compound include a conductive polymer such as polyaniline. Further, the above-mentioned various active materials may be mixed and used regardless of an inorganic compound or an organic compound.

Further, as a compound as a negative electrode material, A
Alloys of lithium with l, Si, Pb, Sn, Zn, Cd, etc., transition metal oxides such as LiFe2O3, WO2, MoO2, carbonaceous materials such as graphite, carbon, Li5
Lithium nitride such as (Li3N) or metallic lithium foil, or a mixture thereof may be used.

[0028]

Next, the present invention will be described based on preferred embodiments.

Example 1 In a non-aqueous electrolyte secondary battery according to the present invention, an elliptical wound-type power generating element composed of a positive electrode plate, a separator and a negative electrode plate is made of metal together with a non-aqueous electrolyte (not shown). It is housed in a bag-shaped unit cell case formed by heat-sealing a laminated resin film, and its appearance is shown in FIG.

A lithium cobalt composite oxide was used as a positive electrode active material. The positive electrode plate is obtained by holding the above-mentioned lithium cobalt composite oxide as an active material on a current collector. A 20 μm aluminum foil was used as the current collector. For the positive electrode plate, 7 parts of polyvinylidene fluoride as a binder and 4 parts of acetylene black as a conductive agent were mixed together with 89 parts of an active material, and N-
Methylpyrrolidone was added to prepare a paste, and then the mixture was applied to both sides of the current collector material and dried.

The negative electrode plate is prepared by mixing 91 parts of graphite (graphite) as a host substance and 9 parts of polyvinylidene fluoride as a binder on both sides of a current collector, and adding N-methylpyrrolidone as appropriate to form a paste. Was prepared by coating and drying. A 14 μm thick copper foil was used as the current collector of the negative electrode plate.

The separator was a microporous polyethylene membrane, and the electrolyte was a mixed solution of ethylene carbonate: diethyl carbonate = 4: 6 (volume ratio) containing 1 mol / l of LiPF6.

The dimensions of the electrode plate are such that the positive electrode plate has a thickness of 204 μm,
Width 49mm, separator thickness 25μm, width 53mm,
The negative electrode plate has a thickness of 204 μm and a width of 51 mm, and the lead terminals are welded to the positive electrode plate and the negative electrode plate, respectively, and superimposed in order. Was wound in an elliptical shape around the periphery of the power generation element so as to be in parallel with the above, thereby forming a power generation element having a size of 60 × 35 × 3.5 mm.

Then, the insulating portion of the electrode is covered with an electrode width (length of the power generation element parallel to the winding center axis of the power generation element) by a tape for stopping winding made of polypropylene (here, an adhesive is applied on one side). Was attached to the side wall of the power generation element parallel to the winding center axis, and the power generation element was stopped and fixed.

This is accommodated in a metal-laminated resin film case, and the elliptical wound-type power generating element is housed so that the winding center axis is perpendicular to the opening surface of the bag-shaped metal-laminated resin film case, and the lead terminals are fixed. And seal the electrolyte.
Each electrode and the separator were sufficiently wetted, and vacuum injection was performed in such an amount that no free electrolyte solution was present outside the power generating element.

FIG. 3 shows an enlarged cross section (cross section AA 'in FIG. 2) of the lead terminal take-out portion of the battery shown in FIG. In FIG. 3, 6 is a 12 μm PET film for protecting the surface of the outermost layer, 7 is a 9 μm aluminum foil as a barrier layer, and 8 is 100 μm as a heat welding layer.
m is an acid-modified low-density polyethylene layer. A metal laminated resin film case as a bag-shaped unit cell case for an airtight opening is composed of 6, 7, and 8, and a P for protecting the surface of the outermost layer.
The ET film 6 and the aluminum foil 7 as a barrier layer are bonded with a urethane-based adhesive. The positive lead terminal 4 and the negative lead terminal 5 have a thickness of 50 to 100 μm.
Metal conductors such as copper, aluminum and nickel.

Finally, sealing welding is performed to obtain a nominal capacity of 50 mm.
A 0 mAh unit cell was prototyped.

[Embodiment 2] FIG. 1 shows a cross section perpendicular to a winding center axis of an elliptical winding type power generating element of this embodiment. In the negative electrode plate, which is the electrode plate corresponding to the outermost periphery of the elliptical power generating element, the mixture layer is not held at the outermost periphery not facing the positive electrode. Using the negative electrode plate of the present invention, fifty laminated cells having a nominal capacity of 500 mAh as described above were prototyped. Table 1 shows the average of the thicknesses of the 50 batteries and the energy densities at this time.

Comparative Example 1 A negative electrode having a nominal capacity of 5 was prepared by using a negative electrode plate in which the mixture was also held at the outermost peripheral portion not facing the positive electrode.
Fifty laminated cells of 00 mAh were prototyped. Table 1 shows the battery thickness and the energy density at this time.

[0040]

[Table 1]

As shown in Table 1, as compared with the battery of Comparative Example 1, the battery of the present invention can be made thinner by the amount corresponding to the mixture layer of the negative electrode active material at the outermost periphery. ,
Further higher energy density is possible.

Next, in Comparative Example 1 and Example 1 of a 500 mAh laminated single cell, a current of 500 mAh was applied at 25 ° C.
Table 2 shows the results of tests performed on the safety of the battery in an overcharged state by charging the battery to a voltage of 10 V at mA.

After performing constant current / constant voltage charging for 3 hours under the conditions of a current of 500 mA and a voltage of 10 V, a test was performed for safety when a 1 mm needle was inserted into the battery to simulate an internal short circuit. Table 2 shows the results. Note that the numbers in the table are the probabilities of bursting and firing.

[0044]

[Table 2]

As is clear from Table 2, Comparative Example 1 fell into a dangerous state involving rupture and ignition, whereas Example 1 did not cause rupture or ignition and was very safe. The result was obtained. In addition, in the comparative example, the surface temperature of the battery at the time of performing the overcharge test was higher than 500 ° C. in some of the batteries.
The temperature of the battery surface could be suppressed down to ℃.

[0046]

According to the present invention, when the non-aqueous electrolyte secondary battery is in an abnormal state such as overcharge or internal short-circuit, an abnormal temperature rise occurs due to heat generated inside the battery, causing thermal runaway, resulting in rupture or ignition. However, the nonaqueous electrolyte secondary battery according to the present invention has an electrode plate corresponding to the outermost peripheral portion of an oblong power generating element, and a mixture layer is held on an electrode surface that does not face a counter electrode plate facing the separator. It is considered that the heat dissipation was excellent and the heat escape was suppressed. From the above results, by using a power generating element in which both the positive electrode lead terminal and the negative electrode lead terminal are attached to the positive electrode plate and the negative electrode plate in the center of the power generating element, a safe battery can be supplied even in an abnormal state involving heat generation. be able to.

Further, according to the present invention, it is possible to provide a non-aqueous electrolyte battery having a reduced battery thickness, a high energy density, and excellent safety.

[Brief description of the drawings]

FIG. 1 is a sectional view perpendicular to a winding center axis of an elliptical winding type power generating element.

FIG. 2 is an external view of a nonaqueous electrolyte secondary battery.

FIG. 3 is an enlarged cross-sectional view (AA ′ cross section of FIG. 1) of a lead terminal take-out portion of the nonaqueous electrolyte secondary battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bag-shaped unit cell case 2 Power generation element 3 Center axis of winding of power generation element 4 Positive electrode lead terminal 5 Negative electrode lead terminal 6 PET film 7 Aluminum foil 8 Acid-modified low density polyethylene layer 9 Positive electrode mixture layer 10 Positive electrode substrate 11 Negative electrode Agent layer 12 Negative electrode substrate 13 Separator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Murai 1st institution, Nishinosho Nishinosho-machi, Minami-ku, Kyoto, Kyoto Prefecture Inside of Nippon Battery Co., Ltd. (72) Inventor Shinya Kitano, Kichijoin-nishi, Minami-ku, Kyoto, Kyoto No. 1 Inohomaba-cho, No. 1, Japan Battery Co., Ltd. (72) Inventor Hiroyuki Yumoto No. 1 Nishinosho Inomaba-cho, Kisho-in, Minami-ku, Kyoto, Kyoto Prefecture, Japan No. 1, Japan Battery Co., Ltd. (72) Mikio Okada, Kyoto Prefecture 1F, Nippon Battery Co., Ltd. F-term (reference) No. 1 Nishinosho Nishinobaba-cho, Minami-ku, Kyoto AL06 AL07 AL08 AL12 AL16 AM03 AM04 AM07 BJ01 BJ14 DJ02 DJ07 EJ01 EJ11 HJ12

Claims (4)

[Claims] 1. A non-aqueous electrolyte secondary battery in which an oval wound type power generating element having a positive electrode plate, a separator, and a negative electrode plate is housed in a bag-shaped unit cell case, corresponds to the outermost peripheral portion of the oval power generating element. A non-aqueous electrolyte secondary battery, wherein the electrode layer does not hold a mixture layer on an electrode surface that does not face a counter electrode plate opposed to the electrode plate with a separator interposed therebetween. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the electrode plate corresponding to the outermost periphery of the elliptical power generating element is a negative electrode plate. 3. A bag-shaped unit cell case has an airtight structure, and an oval wound type power generating element is housed such that its winding center axis is perpendicular to an opening surface of the bag-shaped unit cell case. The non-aqueous electrolyte secondary battery according to claim 1, wherein: 4. The material of the bag-shaped unit cell case is a metal laminated resin film.
The nonaqueous electrolyte battery according to any one of the preceding claims.