JPH1131496A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the connection strength of a terminal and a lead by fixing a lead of a belt-like metal plate to a terminal, which connects each electrode to each lead and which is formed of a belt-like metal plate having multiple holes, so that the lead envelopes a tip of the terminal. SOLUTION: A positive lead 10 formed of a belt-like metal plate has a double folding part 11, which is formed by folding one end into three, and tips of three positive electrode terminals 6 are arranged in this double folding part 11 in the one bound condition, and fixed by welding or the like. Similarly, a negative electrode lead has a double folding part, which is formed by folding one end into three, and tips of two negative electrode terminals are arranged in this double folding part in the one bound condition, and fixed by welding or the like. Connecting strength between each terminal and each lead is thereby improved, and capacity can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a lead comprising one or more electrodes, a band-shaped metal plate, and a terminal portion comprising a band-shaped metal plate having a plurality of holes for connecting the electrodes and the leads. And a battery comprising:

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, there has been a demand for the development of a secondary battery that is small, lightweight, has a high energy density, and can be repeatedly charged and discharged. As such a secondary battery, a negative electrode using lithium or a lithium alloy as an active material, and a suspension containing an oxide, sulfide, or selenide as an active material, such as molybdenum, vanadium, titanium, or niobium, were applied. A lithium secondary battery including a positive electrode made of a current collector and a non-aqueous electrolyte is known.

Further, for example, coke, graphite, carbon fiber,
There has been proposed a lithium secondary battery using, as a negative electrode, a current collector coated with a suspension containing a carbonaceous material that stores and releases lithium ions, such as a resin fired body and pyrolytic gas phase carbon.

A polymer electrolyte secondary battery, which is an example of a lithium secondary battery, has at least one positive electrode, at least one negative electrode, and a lithium ion conductive solid electrolyte layer interposed between each of the positive electrodes and each of the negative electrodes. And Each of the positive electrodes has a structure in which a positive electrode layer containing an active material such as a lithium composite oxide is supported on a current collector. On the other hand, each of the negative electrodes has a structure in which a negative electrode layer containing an active material such as a carbonaceous material capable of inserting and extracting lithium ions is supported on a current collector. In such a secondary battery, in order to improve the energy density per unit weight by increasing the amount of the positive electrode layer and the negative electrode layer carried on the current collector, as a current collector of the positive electrode and the negative electrode, Metal nets are used. Specifically, an expanded metal made of aluminum is used as the current collector of the positive electrode, and an expanded metal made of copper is used as the current collector of the negative electrode. Further, each of the current collectors has a band-shaped terminal portion, and the terminal portion is formed of a metal net made of the same material as the current collector. further,
A positive electrode lead made of, for example, a band-shaped aluminum foil is connected to the terminal portion of the positive electrode by, for example, resistance welding. On the other hand, a negative electrode lead made of, for example, a strip-shaped copper foil is connected to the terminal portion of the negative electrode by, for example, resistance welding. However, it is difficult to connect the metal net and the metal foil with high welding strength, and there has been a problem that the lead comes off from the terminal portion.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a battery capable of increasing the connection strength between a terminal portion and a lead.

[0006]

According to the present invention, there are provided at least one electrode, a lead made of a strip-shaped metal plate, and a strip-shaped metal plate having a large number of holes connecting the electrodes and the leads. A battery provided with a terminal portion, wherein the lead is fixed to the terminal portion so that the lead surrounds a tip of the terminal portion.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a battery according to the present invention will be described in detail using a polymer electrolyte secondary battery as an example. An example of the polymer electrolyte secondary battery will be described with reference to FIGS.

That is, the power generating element of the secondary battery has three
There is provided a nine-layer laminate formed by alternately stacking one positive electrode 1 and two negative electrodes 2 with a solid electrolyte layer 3 interposed therebetween. Each of the positive electrodes 1 includes a current collector 4 made of, for example, a metal net, and an active material layer 5 that absorbs and releases lithium ions stacked on both surfaces of the current collector 4. Further, as shown in FIG. 2, each of the positive electrodes 1 has, on the current collector 4, a terminal portion 6 made of, for example, a band-shaped metal net. On the other hand, each of the negative electrodes 2 includes a current collector 7 made of, for example, a metal net, and an active material layer 8 that absorbs and releases lithium ions stacked on both surfaces of the current collector 7. Further, as shown in FIG. 3, each of the negative electrodes 2 has a terminal portion 9 made of, for example, a band-shaped metal net on the current collector 7. The terminal portion 9 of each of the negative electrodes 2 is attached at a position where it does not overlap with the terminal portion 6 of each of the positive electrodes 1 in the above-described nine-layer laminate. The positive electrode lead 10 made of a band-shaped metal plate has a two-folded part 11 formed by folding one end into three. The three positive electrode terminal portions 6 are arranged in the folded portion 11 in a state where the tips of the three positive electrode terminal portions 6 are bundled together, and are solidified by, for example, welding. The power generating element also includes a negative electrode lead (not shown) made of a band-shaped metal plate. This lead has a two-folded portion formed by folding one end into three as in the case of the positive electrode lead described above. In the two-folded portion, the tips of the two negative electrode terminal portions are arranged in a bundled state, and are solidified by, for example, welding.

Such a power generating element is housed in a sealed state in a container made of, for example, a laminated film or a metal or resin. As the laminate film, for example, a surface layer having a function as a protective layer (for example, made of an insulating resin such as polyethylene terephthalate (PET)) and one surface of the surface layer are adhered, and moisture enters from the outside. And an inner layer (for example, made of a metal such as aluminum) having a function of blocking
(Made of a heat-fusible resin such as an ionomer resin).

In order to increase the connection strength between the three positive electrode terminal portions 6 and the positive electrode lead 10, it is preferable to fix the two-folded portion 11 with a frame-shaped fixing member 12, as shown in FIG. This fixing member can be formed, for example, by folding a strip-shaped laminated film into two, sandwiching the two-folded portion, and performing heat sealing. Examples of the laminated film include the same as those described above. On the other hand, also at the junction (folded portion) between the negative electrode terminal and the negative electrode lead, it can be fixed with a frame-shaped fixing member in order to increase the connection strength. As the fixing member, the same member as described above can be used.

Hereinafter, the positive electrode 1, the negative electrode 2, and the fixed electrolyte layer 3 will be described. (Positive Electrode 1) The active material layer (positive electrode layer) 5 of the positive electrode 1 includes an active material, a non-aqueous electrolyte, and a polymer holding the electrolyte.

As the active material, various oxides (for example, lithium manganese composite oxide such as LiMn ₂ O ₄ ,
Manganese dioxide, for example, a lithium-containing nickel oxide such as LiNiO ₂ , for example, a lithium-containing cobalt oxide such as LiCoO ₂ , a lithium-containing nickel cobalt oxide, and an amorphous vanadium pentoxide containing lithium.
And chalcogen compounds (for example, titanium disulfide, molybdenum disulfide, and the like). Among them, it is preferable to use a lithium manganese composite oxide, a lithium-containing cobalt oxide, and a lithium-containing nickel oxide.

The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent. As the non-aqueous solvent,
Ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DE
C), ethyl methyl carbonate (EMC), γ-butyrolactone (γ-BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (TH
F) and 2-methyltetrahydrofuran. The non-aqueous solvents may be used alone or as a mixture of two or more.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ) and lithium hexafluorophosphate (L
iPF ₆ ), lithium borotetrafluoride (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN
(CF ₃ SO ₃ ) ₂ ].

It is desirable that the amount of the electrolyte dissolved in the non-aqueous solvent be 0.2 mol / l to 2 mol / l. Examples of the polymer holding the nonaqueous electrolyte include a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the derivative, and a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP). Can be. The copolymerization ratio of the HFP depends on the method of synthesizing the copolymer, but is usually at most about 20% by weight.

[0016] The positive electrode layer may contain a conductive material from the viewpoint of improving conductivity. Examples of the conductive material include artificial graphite, carbon black (eg, acetylene black), nickel powder, and the like.

As the metal net as the current collector 4, for example, an expanded metal made of aluminum, a mesh made of aluminum, a punched metal made of aluminum, or the like can be used.

The current collector 4 has a thickness of 10 μm to 100 μm.
It is preferable to set it in the range of μm. As the metal net constituting the strip-shaped terminal portion 6, for example, a metal net similar to that described in the above-described current collector 4 can be used.

The thickness of the terminal portion 6 is 10 μm to 100 μm.
It is preferable to set it in the range of μm. The positive electrode lead 11
Can be formed, for example, from an aluminum foil. (Negative Electrode 2) The active material layer (negative electrode layer) 8 of the negative electrode 2 contains an active material, a non-aqueous electrolyte, and a polymer holding the electrolyte.

Examples of the active material include carbonaceous materials that occlude and release lithium ions. Such carbonaceous materials include, for example, those obtained by firing organic polymer compounds (eg, phenolic resin, polyacrylonitrile, cellulose, etc.), those obtained by firing coke and mesophase pitch, and those made by artificial graphite. And carbonaceous materials represented by natural graphite and the like. Among them, 500
It is preferable to use a carbonaceous material obtained by calcining the mesophase pitch at a temperature of from ℃ to 3,000 ℃ under normal pressure or reduced pressure.

As the non-aqueous electrolyte and the polymer, the same ones as those described for the positive electrode are used. The negative electrode layer is made of artificial graphite, natural graphite, carbon black, acetylene black,
It is allowed to contain conductive materials such as Ketjen black, nickel powder, and polyphenylene derivatives, and fillers such as olefin polymers and carbon fibers.

As the metal net as the current collector 7, for example, copper expanded metal, copper mesh, copper punched metal, or the like can be used. The thickness of the current collector 7 is preferably in the range of 10 μm to 100 μm.

As the metal net forming the strip-shaped terminal portion 9, the same metal net as the above-mentioned current collector 7 can be used. It is preferable that the thickness of the terminal portion 9 be in a range of 10 μm to 100 μm.

As the negative electrode lead, a metal foil such as a copper foil can be used. (Solid Polymer Electrolyte Layer 3) The electrolyte layer 3 contains a non-aqueous electrolyte and a polymer holding the electrolyte.

As the non-aqueous electrolyte and the polymer, those similar to those described for the positive electrode described above are used. The electrolyte layer is made of S in order to improve compressive strength.
An inorganic filler such as iO ₂ powder may be added.

As described in detail above, the battery according to the present invention comprises:
Such a battery can improve the connection strength between the terminal portion and the lead. As a result, a high-capacity battery can be provided with a high yield.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail. Example 1 <Preparation of Positive Electrode> A lithium manganese composite oxide represented by a composition formula of LiMn ₂ O ₄ as an active material, carbon black, and vinylidene fluoride-hexafluoropropylene (VdF-HFP). The combined powder and dibutyl phthalate (DBP) were mixed in acetone to prepare a paste. The obtained paste is put on a polyethylene terephthalate film (PET film) to a thickness of 100 μm.
m, formed into a sheet, and cut to obtain a positive electrode sheet. Also, a current collector having a strip-shaped terminal portion made of an expanded metal made of aluminum was prepared. The terminal had a width of 10 mm, a length of 10 mm, and a thickness of 50 μm. Further, the current collector has a width of 43 mm.
And the length was 52 mm and the thickness was 45 to 55 μm. The obtained sheet was heated and pressed on both sides of the current collector with a hot roll to produce a positive electrode not impregnated with a non-aqueous electrolyte.

<Preparation of Negative Electrode> Mesophase pitch carbon fiber as an active material, vinylidene fluoride-hexafluoropropylene (VdF-HFP) copolymer powder,
Mixing dibutyl phthalate (DBP) in acetone,
A paste was prepared. The obtained paste was applied on a polyethylene terephthalate film (PET film) so as to have a thickness of 100 μm, formed into a sheet, and cut to prepare a negative electrode sheet. Further, a current collector having a strip-shaped terminal portion made of a copper expanded metal was prepared. The terminal had a width of 10 mm, a length of 10 mm, and a thickness of 50 μm. The current collector has a width of 45 m.
m, length 54 mm and thickness 45-55 μm. The obtained negative electrode sheet was heat-pressed on both surfaces of the current collector with hot rolls to produce a non-aqueous electrolyte-unimpregnated negative electrode.

[0029] <Preparation of solid electrolyte layer> and SiO ₂ powder,
Vinylidene fluoride-hexafluoropropylene (V
dF-HFP) and dibutyl phthalate (DBP) were mixed in acetone to form a paste. The obtained paste was applied on a polyethylene terephthalate film (PET film) so as to have a thickness of 100 μm and a width of 200 mm, thereby producing a non-aqueous electrolyte-unimpregnated separator sheet.

<Preparation of Nonaqueous Electrolyte> A nonaqueous electrolyte was prepared by dissolving LiPF ₆ as an electrolyte in a nonaqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed.

<Assembly of Battery> Three positive electrodes, two negative electrodes, and four solid electrolyte layers were prepared, and the positive electrode and the negative electrode were alternately laminated with the solid electrolyte layer interposed therebetween. These were heat-pressed with a rigid roll heated to 130 ° C. to produce a laminate. Such a laminate was immersed in methanol, and the DBP in the laminate was extracted with methanol and removed. Subsequently, the laminate was dried, and immersed in a non-aqueous electrolyte having the above composition to impregnate the laminate with the electrolyte. Strip-shaped aluminum foil as a positive electrode lead (width 10 mm, length 50 mm
Then, the end part having a thickness of 30 μm) was folded in three to form a folded part. The tips of the above-mentioned three positive electrode terminal portions are overlapped, and these terminal portions are arranged in the above-mentioned folded portion, and are subjected to ultrasonic welding (welding time 0.02 (sec), output 1).
50 (W), pressure 10 (psi)).
In addition, a strip-shaped copper foil as a negative electrode lead (with a width of 10 mm,
The end having a length of 50 mm and a thickness of 30 μm) was folded in three to form a folded part. The tips of the two negative electrode terminals described above are overlapped with each other, these terminal portions are arranged in the above-described two-folded portion, and these are ultrasonically welded (welding time 0.1 mm).
(Sec), output 450 (W), pressure 15 (psi))
Thus, a power generating element for a polymer electrolyte secondary battery as shown in FIG. 1 was manufactured.

(Example 2) A power generating element similar to that of Example 1 was manufactured. A strip-shaped laminated film (width: 5 mm, length: 25 mm, thickness: 100 μm) including a surface layer made of polyethylene terephthalate, an intermediate layer made of aluminum, and an inner layer made of an ionomer resin was prepared. By folding this film into two parts, sandwiching the junction between the positive electrode terminal part and the positive electrode lead (two-fold part) with this film, and performing heat sealing from above and below the film, as shown in FIG. The joint was fixed with a band-like laminated film. Folding a band-shaped film having the same material and dimensions as described above into two, sandwiching the junction (folded portion) between the negative electrode terminal and the negative electrode lead with this film, and performing heat sealing from above and below the film Thus, the joint was fixed with a band-shaped laminate film.

(Comparative Example) A power generating element similar to that of Example 1 was manufactured except that the terminal portion and the lead were fixed by the method described below.

That is, the tips of the two positive electrode terminals are overlapped, placed on the upper surface of the end of the positive electrode lead similar to that of the first embodiment, and the tips of the remaining positive electrode terminals are connected to the lower surface of the end of the positive electrode lead. And these are ultrasonically welded (with a welding time of 0.
02 (sec), output 150 (W9, pressure 10 (ps)
Bonded according to i)). On the other hand, the tip of the negative electrode lead similar to that of Example 1 is disposed between the tips of the two negative electrode terminals,
These were bonded by ultrasonic welding (welding time 0.1 (sec), output 450 (W), pressure 15 (psi)),
A power generation element for a polymer electrolyte secondary battery was manufactured.

With respect to the power generation elements obtained in Examples 1 and 2 and Comparative Example, five pieces were prepared, and the end of the positive electrode lead was pulled at a pulling speed of 20 mm / min. (Kg / 10 mm), and the results are shown in Table 1 below.

Further, five secondary batteries of Examples 1 and 2 and a comparative example were prepared, and the ends of the negative electrode lead were pulled at a pulling speed of 20 mm / min, and the tensile strength when the terminal portion was cut off. (Kg / 10 mm) and the results are shown in Table 1 below.

Table 1 Positive electrode / tensile strength Negative electrode / tensile strength Example 1 1.5 (kg / 10 mm) 1.2 (kg / 10 mm) Example 2 2.6 (kg / 10 mm) 2.5 (kg / 10 mm) ) Comparative Example 0.8 (kg / 10mm) 0.6 (kg / 10mm) As is clear from Table 1, the tips of a plurality of terminal portions made of a strip-shaped metal plate having a large number of holes are bundled into one, and Examples 1 and 2 having a structure in which a lead made of a band-shaped metal plate is attached so as to wrap around them,
It turns out that the tensile strength of the positive electrode lead and the negative electrode lead is higher than that of the comparative example. Particularly, in the second embodiment in which the joint between the terminal portion and the lead is fixed by a frame-shaped fixing member, the tensile strength of the positive electrode lead and the negative electrode lead can be improved as compared with the first embodiment.

On the other hand, in the comparative example in which the terminal portions are fixed to both surfaces of the lead, it can be seen that the lead is broken off from the welded portion with the terminal portion by a weaker force as compared with the embodiment. In the above-described embodiment, the example in which the terminal portion and the lead are fixed by ultrasonic welding is described. However, the fixing may be performed by resistance welding.

[0039]

As described above in detail, according to the present invention, it is possible to improve the connection strength between a terminal portion formed of a metal plate having a large number of holes and a lead formed of a band-shaped metal plate, thereby increasing the capacity. It has remarkable effects such as being able to achieve.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a power generating element of a polymer electrolyte secondary battery as an example of a battery according to the present invention.

FIG. 2 is a top view showing a positive electrode included in the power generating element of FIG.

FIG. 3 is a top view showing a negative electrode included in the power generating element of FIG. 1;

FIG. 4 is a partial top view showing another example of the battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 2 ... Negative electrode, 3 ... Solid electrolyte layer, 4 ... Positive electrode collector, 5 ... Active material layer, 6 ... Positive electrode terminal part 7 ... Negative electrode current collector, 8 ... Active material layer, 10 ... Positive electrode lead.

Claims (1)

[Claims] 1. A battery comprising one or more electrodes, a lead made of a strip-shaped metal plate, and a terminal part connecting the electrodes and the leads and made of a strip-shaped metal plate having a large number of holes. The battery, wherein the lead is fixed to the terminal portion so that the lead wraps a tip of the terminal portion.