JP2000277066A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the pressure resistance while preventing the peeling of a welding part when the inner pressure of a battery rises by providing a resin block in an inside end of a welding part of a bag-like unit cell case for housing a power generating element having a positive plate, a separator and a negative plate. SOLUTION: A bag-like cell case desirably has the airtight structure, and houses an elliptic winding type power generating element 2 so that the winding center axis thereof is arranged vertical to an opening surface of the case. A metal laminated resin film is overlapped so as to face to a heat welding layer 13, and an inside end of the heat welding layer 13 welded by heat is pressed so as to be formed into a resin block 14 having the predetermined thickness, and thereafter, the metal laminated resin film is overlapped more, and sealed by heat welding. The stress is distributed to both ends of the resin block 14 without directly applying to a bonding interface formed into a curved surface, and pressure resistance at about twice of the battery case can be obtained. Thickness X of the outside end of the heat welding layer 13 is desirably formed smaller than the thickness Y of the inside end, and a contact area with the atmospheric air is reduced so as to restrain permeation of the moisture and evaporation of the electrolyte at the seal part, and longtime storage property under the high temperature condition is improved.

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 a lithium 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]

Generally, a metal-laminated resin film used for a bag-shaped unit cell case has a structure in which a metal foil and a resin layer are adhered to one or both sides of the metal foil. An airtight structure in the direction of transmission through the film surface is achieved by using no material. In addition, the resin layer is provided with a film surface that can be sealed by a method such as heat welding or the like after reinforcing the tensile strength, piercing strength, bending weakness, and the like of the metal foil generally having spreadability, or housing the power generating element. It has the function of imparting adhesiveness.

However, when the battery generates heat due to the battery being overcharged or an internal short circuit occurring,
When the battery is left under high temperature and the pressure inside the battery rises, the welded portion inside the battery peels off because the metal laminated resin film concentrates on the bent portion near the welded portion inside the battery, and the hermetic leakage of the battery is reduced. In the worst case, there is a problem that the liquid leaks.

Further, in a bag-shaped single cell case,
It is important to suppress the permeation of moisture and gas components from the outer surface of the battery to the inside of the battery with the power generating element or the evaporation of the electrolyte from the inside of the battery to the outside. When used as a material, although the airtightness in the surface direction of the film can be maintained by the metal foil, there is a problem that moisture and electrolyte components permeate the resin layer between the metal foils at the sealing portion.

Accordingly, the present invention provides a method for preventing a battery from being heated due to an overcharged state or an internal short-circuit, and a welded portion of a metal laminated resin film does not peel off even if the battery is left at a high temperature. An object is to provide a non-aqueous electrolyte secondary battery having excellent airtightness.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has been made in consideration of the above problems. A non-aqueous electrolyte secondary battery in which a power generating element having a positive electrode plate, an isolator, and a negative electrode plate is housed in a bag-shaped unit cell case. In the battery, a resin lump is provided at an inner end of the bag-shaped unit cell case welded portion.

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. It should be noted that the vertical direction does not only mean a completely vertical direction but also a substantially vertical direction.

Further, the present invention is characterized in that the thickness of the inner end of the welded portion of the bag-shaped unit cell case is larger than the thickness of the outer end.

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

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings, taking a battery provided with an elliptical winding type power generating element as an example. The external appearance of the nonaqueous electrolyte secondary battery according to the present invention is shown in FIG. 1, 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. In FIG. 1, 1 is a bag-shaped single cell case, 2 is a power generating element, 3 is a winding central axis of the power generating element, 4 is a positive electrode lead terminal, and 5 is a negative electrode lead terminal. FIG. 2 is an enlarged cross-sectional view of a welded portion of a bag-shaped unit cell case according to the first embodiment of the present invention (cross section taken along the line BB ′ in FIG. 1).
It is. In FIG. 2, reference numeral 2 denotes a power generating element, 11 denotes a surface protective layer, 12 denotes a metal barrier layer, and 13 denotes a heat welding layer. Then, a resin block 14 is provided at the inner end of the welded portion of the bag-shaped unit cell case. The thickness X of the outer end of the welded portion of the bag-shaped unit cell case is equal to the thickness Y of the inner end.

FIG. 3 is an enlarged cross-sectional view of a welded portion of a bag-shaped unit cell case according to a second embodiment of the present invention (cross section taken along the line BB 'in FIG. 1).
It is. Symbols 2, 11 to 14 in FIG. 3 indicate the same as those in FIG. 2. The resin block 14 is provided at the inner end of the welded portion of the bag-shaped unit cell case, and the thickness Y of the inner end is larger than the thickness X of the outer end of the welded portion of the bag-shaped unit cell case. ing.

The shape of the power generating element used in the present invention is not limited to an elliptical wound type in cross section, but may be a circular wound type, a non-circular wound type in cross section, or a flat plate-type electrode plate. A power generating element having any shape can be used, such as a stack type in which the sheet-shaped electrode plate is folded and a type in which the sheet-shaped electrode plate is folded and stacked through a separator.

Further, in the present invention, a bag-shaped unit cell case having an airtight structure can be used, and a metal laminated resin film is preferably used as a material of the bag-shaped unit cell case.

In the present invention, when the elliptical wound type power generating element is stored in the bag-shaped unit cell case, the winding center axis of the elliptical 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.

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

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

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 single cell case include a laminated case formed by heat-welding a metal-laminated resin film into an envelope shape, a case in which four sides of two metal-laminated resin sheets are heat-sealed, and a single sheet. 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.

The electrolyte solvent used in the non-aqueous electrolyte secondary battery according to the present invention includes ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide. , 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 lithium salt dissolved in an organic solvent includes LiPF6, LiClO4, LiBF4, LiAs
F6, LiCF3CO2, LiCF3SO3, LiN
(SO2CF3) 2, LiN (SO2CF2CF3)
2, LiN (COCF3) 2 and LiN (COCF2)
A salt such as CF3) 2 or a mixture thereof may be used.

The separator of the non-aqueous electrolyte secondary battery according to the present invention may be a material obtained by impregnating an electrolytic solution in a microporous insulating polyethylene membrane, a solid polymer electrolyte, or a solid polymer electrolyte containing an electrolytic solution. 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.

[0031]

Next, the present invention will be described based on preferred embodiments. [Comparison of Welding Strength] [Example 1] In a non-aqueous electrolyte secondary battery according to the present invention, an elliptical wound type power generating element including a positive electrode plate, a separator, and a negative electrode plate is a non-aqueous electrolyte (not shown). ) Is housed in a bag-shaped single cell case obtained by heat-welding a metal laminated resin film together with the above, and its appearance is shown in FIG.

As the positive electrode active material, a lithium cobalt composite oxide was used. The positive electrode plate is obtained by holding the lithium-cobalt composite oxide as an active material on a 20-μm-thick aluminum foil current collector. The positive electrode plate was prepared by mixing 6 parts of polyvinylidene fluoride as a binder and 3 parts of acetylene black as a conductive agent together with 91 parts of an active material, appropriately adding N-methylpyrrolidone to prepare a paste, and then collecting the paste. It was manufactured by applying and drying both sides of an electric conductor material.

The negative electrode plate is a copper foil current collector having a thickness of 14 μm,
It was prepared by mixing 92 parts of graphite (graphite) as a host substance and 8 parts of polyvinylidene fluoride as a binder, adding N-methylpyrrolidone as appropriate, preparing a paste, and applying and drying the paste. The separator is a polyethylene microporous membrane, and the electrolyte is LiPF6
Of 1 mol / l of ethylene carbonate: diethyl carbonate = 3: 7 (volume ratio).

The dimensions of the electrode plate are as follows: the positive electrode plate has a thickness of 185 μm;
Width 42mm, separator thickness 25μm, width 45mm,
The negative electrode plate has a thickness of 160 μm and a width of 43.5 mm, and the lead terminals are welded to the positive electrode plate and the negative electrode plate, respectively, and superimposed in order, centering on a rectangular core of polyethylene,
The long side is wound in an elliptical spiral shape so that the long side is parallel to the winding center axis of the power generation element, and is 48 × 27.3 × 3.23 m
m power generating element.

Then, the insulating portion of the electrode is covered with a winding tape made of polypropylene (here, an adhesive is applied on one side) to the electrode width (the length of the power generation element parallel to the winding central axis of the power generation element). 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 housed 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. 4 shows a section (section AA 'in FIG. 1) of the welded portion of the lead terminal take-out portion of the battery shown in FIG. In FIG. 4, reference numeral 11 denotes a surface protective layer;
Is a metal barrier layer, 13 is a heat welding layer, 14 is a positive electrode lead terminal, and 15 is a negative electrode lead terminal.

The positive electrode lead terminal 14 and the negative electrode lead terminal 15 are made of a metal conductor such as copper, aluminum, nickel or the like having a thickness of 50 to 100 μm. A metal-laminated resin film case as a bag-shaped unit cell case for an airtight opening is made of 12 μm PE as a surface protective layer in the outermost layer.
A T film 11, a 9 μm aluminum foil 12 as a barrier layer, and a 150 μm acid-modified low-density polyethylene layer 13 as a heat-welding layer. The outermost PET film 11 for surface protection and the aluminum foil as a barrier layer Reference numeral 12 is bonded with a urethane-based adhesive.

FIG. 2 is an enlarged cross-sectional view (cross-sectional view taken along the line BB ′ of FIG. 1) of the bag-shaped unit cell case welding portion of the battery according to the first embodiment of the present invention. A resin block 14 was provided at the inner end of the welded portion of the metal laminated resin film case.

The metal-laminated resin film was placed on top of the metal-laminated resin film case by laminating the metal-laminated resin films so that the heat-welded layers faced each other, and by heat-welding at a welding temperature of 250.degree. A resin mass 14 is formed at the inner end of the welded portion, a metal laminated resin film is overlaid, and sealing is performed by heat welding.
Finally, sealing welding was performed to produce a nonaqueous electrolyte battery in which a power generation element was housed in a bag-shaped battery case in which a resin mass was provided at the inner end of the welded portion of the metal laminated resin film case. The nominal capacity of this battery was 420 mAh. Embodiment 2 FIG. 3 is an enlarged cross-sectional view (cross section taken along the line BB 'of FIG. 1) of a bag-like unit cell case welded portion of a battery according to a second embodiment of the present invention. The metal laminated resin film is overlapped so that the heat-welded layer faces each other, and is heat-welded using a jig having a press surface inclined at the time of heat welding, and the thickness of the outer end of the metal-laminated resin film case welded portion. 10
0 μm, and the thickness of the inner end is 250 μm to form a resin mass 14 at the inner end of the welded portion of the metal laminated resin film case, and the outer end of the welded portion of the metal laminated resin film case. Thickness X
A non-aqueous electrolyte battery (nominal capacity: 420 m) in which a power generation element is housed in a bag-shaped battery case
Ah). [Comparative Example] Cross-sectional enlarged view of a welded portion of a bag-shaped unit cell case of a conventional battery experimentally manufactured as a comparative example (cross section taken along the line BB 'in FIG. 1).
Is shown in FIG. Symbols 2, 11, 12, 13 in FIG.
Shows the same thing as FIG. In the conventional product, the resin mass is not provided at the inner end of the welded portion of the metal laminated resin film case, and the thickness X of the outer end of the welded portion of the metal laminated resin film case is equal to the thickness Y of the inner end. ing.

Here, in Examples 1 and 2 and Comparative Example,
Table 1 shows the results of measuring the pressure resistance of the metal laminated resin film case.

The measuring method was as follows. Using the metal laminated resin film cases of Examples 1 and 2 and Comparative Example, water pressure was applied to the inside of the cases, and the water pressure when the welded portion of the metal laminated resin film case was peeled off was measured.

[0043]

[Table 1]

In the batteries of Examples 1 and 2 in which a resin mass was provided at the inner end of the welded portion of the metal laminated resin film case,
The opening pressure increased about twice as compared with the battery of the comparative example. This is because, in the battery of the comparative example, stress was applied only to the bonding interface of the resin portion of the metal laminate resin film case, whereas in the batteries of Examples 1 and 2, the bonding interface was curved. It is considered that the pressure is distributed to both ends of the resin mass without the stress being directly applied to the joint interface, so that the withstand voltage of the battery case is improved about twice.

As is clear from the above results, the pressure resistance of the metal-laminated resin film case can be significantly improved by providing the resin mass at the inner end of the welded portion of the metal-laminated resin film case. . Further, even in a situation where the battery is overcharged, the battery generates heat due to an internal short circuit, or the internal pressure increases due to being left at a high temperature, the welded portion of the metal laminated resin film is peeled off. Thus, a non-aqueous electrolyte secondary battery having excellent airtightness can be supplied. [Comparison of the difference in thickness between the end face of the welded portion and the base of the welded portion] [Example 3] Next, a form of a battery according to a third embodiment of the present invention will be described. The cross-sectional structure of the welded portion of the metal laminated resin film case is the same as that shown in FIG. 3, but the thickness of the end of the welded portion is changed. Further, a non-aqueous electrolyte secondary battery in which a resin lump is provided in a welded portion inside the metal laminated resin film case, and a difference in thickness between an inner end portion and an outer end portion of the welded portion of the metal laminated resin film is provided. Produced.

Specifically, the thickness of the outer end of the welded portion is set to 2
50 μm, and the thickness of the inner end of the welded portion is 250, 24
By setting the thickness to 5, 240, 200, 150, and 50 μm, the thickness difference between the inner end and the outer end of the welded portion is 0,
5, 10, 50, 100, and 200 μm batteries were fabricated, and the effect of the difference in thickness between the inner end portion and the outer end portion of the welded portion was examined.

These batteries were fully charged by charging them at a constant current / constant voltage for 4 hours under the conditions of a current of 400 mA and a voltage of 4.1 V, left at 60 ° C. for 1 month, and compared the capacities of the batteries before and after leaving. did. Further, the amount of water increase in the electrolyte after standing and the amount of evaporation of the electrolyte were measured.

Table 2 shows the results of a 60 ° C. × 1 month standing test.

[0049]

[Table 2]

In the third embodiment, by making the thickness of the outer end portion smaller than the thickness of the inner end portion of the welded portion, the entry of water into the battery and the evaporation of the electrolytic solution out of the battery are suppressed.
Battery preservability has improved. At the welded part of the metal laminated resin film, there is no metal part which is a barrier layer to prevent the invasion of water and the evaporation of the electrolyte to the outside. Therefore, the penetration of water and the evaporation of the electrolyte to the outside via the heat welding layer Is more likely to occur.

When moisture enters the inside of the battery, it reacts with LiPF ₆ in the electrolytic solution to generate HF, corroding aluminum which is a positive electrode current collector, thereby increasing the internal resistance of the battery, Reacts with the electrolyte to form a film, thereby causing a decrease in battery capacity. Therefore, by making the thickness of the end face of the welded portion smaller than the thickness of the base portion of the welded portion, the contact area between the welded portion and the atmosphere can be reduced, and the path through which moisture and the electrolytic solution permeate can be reduced. Since intrusion into the inside and evaporation of the electrolytic solution to the outside can be suppressed, deterioration in battery performance can be suppressed, and long-term storage of the battery has become possible.

[0052]

According to the present invention, by providing a resin mass inside the battery of the metal laminated resin film case,
The stress applied to the welded portion can be dispersed even under a situation where the internal pressure of the battery rises, and the metal-laminated resin film case welded portion does not peel off, so that a battery excellent in pressure resistance can be obtained.

Further, by making the thickness of the outer end portion of the welded portion of the metal laminated resin film case smaller than the thickness of the inner end portion, the contact area between the atmosphere and the battery case seal portion is reduced, and the permeation through the seal portion is achieved. Suppresses evaporation of moisture and electrolyte, and has excellent long-term storage characteristics even at high temperatures.
In addition, a non-aqueous electrolyte secondary battery having excellent pressure resistance and airtightness can be supplied.

In addition, since the battery is excellent in airtightness, a metal laminate as a bag-shaped unit cell case is provided, which does not cause deterioration of battery characteristics, is highly safe, and does not cause complicated manufacturing process. It is possible to provide a nonaqueous electrolyte battery in which an elliptical wound power generation element is stored in a resin film case.

[Brief description of the drawings]

FIG. 1 is an external view of a nonaqueous electrolyte secondary battery.

FIG. 2 is an enlarged cross-sectional view of a non-aqueous electrolyte secondary battery according to the first embodiment of the present invention, taken along a line BB ′ in FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a non-aqueous electrolyte secondary battery according to a second embodiment of the present invention, taken along a line BB ′ in FIG. 1;

FIG. 4 is a view showing a cross section (AA ′ cross section in FIG. 1) of a welded portion of a lead terminal take-out portion of the nonaqueous electrolyte secondary battery according to the present invention.

5 is an enlarged cross-sectional view of a welded portion of a bag-shaped unit cell case of the nonaqueous electrolyte secondary battery according to Embodiment 3 of the present invention (B- in FIG. 1).
B 'section).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bag-shaped unit battery case 2 Power generation element 3 Center axis of winding of power generation element 4 Positive electrode lead terminal 5 Negative electrode lead terminal 11 Surface protective layer 12 Metal barrier layer 13 Thermal welding layer 14 Resin lump

 ──────────────────────────────────────────────────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) 5H011 AA13 CC02 CC06 CC10 DD13 EE04 FF02 GG09 HH02 HH13 JJ25 KK01 5H029 AJ11 AJ12 AK02 AK03 AK05 AK16 AL02 AL03 AL06 AL07 AM03 AM04 AM05 AM07 BJ01 BJ14 DJ02 DJ03 EJ01 EJ11 HJ12

Claims (4)

[Claims] In a non-aqueous electrolyte secondary battery in which a power generating element having a positive electrode plate, a separator, and a negative electrode plate is housed in a bag-shaped unit cell case, a resin block is formed at the inner end of the bag-shaped unit cell case welding portion. A non-aqueous electrolyte secondary battery, which is provided. 2. A bag-shaped unit cell case has an airtight structure, and an oval wound type power generating element is housed such that a winding center axis thereof is perpendicular to an opening surface of the bag-shaped unit cell case. The non-aqueous electrolyte secondary battery according to claim 1, wherein: 3. The thickness of the inner end of the welded portion of the bag-shaped unit cell case is larger than the thickness of the outer end.
The non-aqueous electrolyte secondary battery according to claim 1. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the material of the bag-shaped unit cell case is a metal laminated resin film.