JP3508151B2 - Battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery, and more particularly to improvement of welding strength in a battery in which one of lead plates connected to a positive electrode collector and a negative electrode collector is welded to the inner surface of a battery can.

[0002]

2. Description of the Related Art In recent years, in the field of batteries, with the widespread use of portable devices such as video cameras and radio cassettes, there is an increasing demand for secondary batteries that can be repeatedly used instead of disposable primary batteries.

Most of the secondary batteries currently used are nickel-cadmium batteries using an alkaline electrolyte.
However, since the voltage of this battery is about 1.2 V, it is difficult to improve the battery energy density. Also,
There is also a drawback that the self-discharge rate at room temperature is as high as 20% or more per month.

Therefore, there has been proposed a non-aqueous electrolyte secondary battery in which a non-aqueous solvent is used as the electrolyte and a light metal such as lithium is used as the negative electrode. This non-aqueous electrolyte secondary battery has a voltage of 3
It has excellent characteristics as a battery having a high energy density of V or more and a low self-discharge rate, and is being studied as a practical battery.

However, in the non-aqueous electrolyte secondary battery in which lithium or the like is used for the negative electrode, metallic lithium or the like used for the negative electrode grows in dendrite form due to repeated charging / discharging and comes into contact with the positive electrode. There is a drawback that a short circuit easily occurs inside, and it is difficult to put it into practical use.

Therefore, it has been attempted to alloy lithium with another metal and use this alloy for the negative electrode.
However, in this case, there is a drawback that the alloy used for the negative electrode is likely to be formed into particles by repeating charging and discharging, which again hinders practical use.

Therefore, as disclosed in JP-A-62-90863, it has been proposed to use a carbonaceous material such as coke as a negative electrode active material.
Since the secondary battery using the carbonaceous material as the negative electrode active material does not have the above-mentioned drawbacks in the negative electrode, excellent cycle life characteristics can be obtained. Then, as the positive electrode active material, Li _x M0 ₂ as described in JP-A-63-135099 (where M represents one or more kinds of transition metals, and 0.05 <X <1.10) is used. When used,
Further, the battery capacity is improved, and it becomes possible to obtain a non-aqueous electrolyte secondary battery having a high energy density.

Although these various non-aqueous electrolyte secondary batteries have some problems to be improved such as internal short circuit and particle formation of the negative electrode alloy, the negative electrode active material is a carbon material, lithium or lithium alloy, etc., and a material having a small specific gravity. Therefore, both are lighter in weight than nickel-cadmium batteries, and are being studied as a power source for portable devices.

Incidentally, the non-aqueous electrolyte secondary battery is specifically constructed as shown in FIG.

That is, the non-aqueous electrolyte secondary battery has a battery can 21 in which an electrode 22 and a non-aqueous solvent are contained. The electrode 22 has a positive electrode 23 formed by attaching Li _x MO ₂ or the like, which is a positive electrode active material, to a strip-shaped current collector, and a lithium, lithium alloy, or carbonaceous material, which is a negative electrode active material, attached to the strip-shaped current collector. The negative electrode 24 thus formed, and the separator 2
5 is alternately laminated, and the laminated body is wound to form a spiral structure.

One end of a negative electrode lead plate 26 is connected to the negative electrode 24 of the spiral-shaped electrode 22.
The other end of the negative electrode lead plate 26 connected to the
It is welded to the inner bottom surface. On the other hand, one end of a positive electrode lead plate 27 is connected to the positive electrode 23 of the spirally configured electrode 22, and the other end of the positive electrode lead plate 26 connected to the positive electrode 23 insulates the upper portion of the battery can 21. It is welded to a battery lid 29 which is closed via a material 28.

[0012]

In order to achieve the above object, the battery of the present invention comprises a positive electrode plate having a positive electrode active material coated on both sides of an aluminum foil current collector, and an end portion of the positive electrode plate. Welded metal positive electrode lead plate, a negative electrode plate having a negative electrode active material applied to both sides of a copper foil current collector, a metal negative electrode lead plate welded to the end of the negative electrode plate, and via a separator It has a battery can in which a spirally wound electrode body formed by winding the laminated positive electrode plate and negative electrode plate is housed, and the positive electrode lead plate or the negative electrode lead plate is a connection portion with the inner surface of the battery can. Is provided with a plurality of hemispherical projections arranged at predetermined intervals, and the hemispherical projections are welded to the inner surface of the battery can. Further, the battery of the present invention is characterized in that the plurality of protrusions provided on the welded portion of the lead plate are protrusions formed by press working. Further, the battery of the present invention is a non-aqueous electrolyte secondary battery in which a carbonaceous material is contained in the negative electrode active material applied to the negative electrode plate and an organic solvent is used as an electrolytic solution. Is. Further, the battery of the present invention is characterized by being a non-aqueous electrolyte secondary battery in which the positive electrode active material applied to the positive electrode plate contains a lithium-cobalt composite oxide material.

Therefore, the present invention has been proposed in view of such conventional circumstances, and the welding strength between the negative electrode lead plate and the inner bottom surface of the battery can is strong, and the welding is destroyed by vibration during portable use. It is an object of the present invention to provide a battery suitable as a power source for portable devices.

[0014]

In order to achieve the above object, the battery of the present invention has a positive electrode and a negative electrode housed in a battery can and is connected to either a positive electrode or a negative electrode current collector. In a battery formed by welding the inner surface of the battery can to the inner surface of the battery can, a plurality of protrusions are provided on the welded portion of the lead plate with the inner surface of the battery can. It is characterized in that the plurality of projections provided are projections formed by press working.

The battery to which the present invention is applied has, for example, a positive electrode and a negative electrode housed in a battery can together with an electrolytic solution. One end of a negative electrode lead plate is connected to the negative electrode, and the other end of the negative electrode lead plate is welded to the inner bottom surface of the battery can. On the other hand, one end of a positive electrode lead plate is connected to the positive electrode, and the other end of the positive electrode lead plate is welded to a battery lid that closes the upper part of the battery can via a gasket made of an insulating material.

According to the present invention, in the battery having such a structure, a plurality of protrusions are provided on a portion of the negative electrode lead plate welded to the inner bottom surface of the battery can. Then, the negative electrode lead plate and the bottom surface of the inside of the battery can are brought into contact with the projection formed on the negative electrode lead plate and the bottom surface of the inside of the battery can, and, for example, current is locally applied to this portion to weld them.

When the negative electrode lead plate and the inner bottom surface of the battery can thus welded together have a plurality of protrusions as welding points, when the inner bottom face of the battery can and the negative electrode lead plate surface are directly welded without interposing the protrusions. Compared to flat surfaces that are welded at a single welding point like the one shown in Fig. 2, both torsional strength and tensile strength are stronger, and they exhibit excellent fracture resistance against vibration when the battery is used in a portable manner. . In addition, it is important that a plurality of protrusions are formed on the portion of the negative electrode lead plate to be welded. When only one protrusion is provided, the tensile strength is improved but the torsional strength is insufficient, and the welded portion The fracture resistance cannot be sufficiently improved.

Further, it is considered that the welding strength can be similarly improved by providing the projection on the bottom surface of the battery can instead of on the side of the negative electrode lead plate. Since it is difficult to accurately align the projection on the bottom surface inside the battery can with the negative electrode lead plate, the manufacturing operation becomes complicated. In the present invention, the reason why the protrusion is provided on the negative electrode lead plate side is to avoid such a difficulty of alignment.

Such a protrusion can be easily formed on the negative electrode lead plate by using, for example, a pressing method.

The present invention can be applied to any of primary batteries, secondary batteries, water-based electrolyte batteries, and non-aqueous electrolyte batteries. However, as described above, the present invention is resistant to vibration during portable use. In particular, it is preferable to use it for a non-aqueous electrolyte secondary battery that is often used as a power source for portable devices.

As the negative electrode, the positive electrode and the electrolyte used in the non-aqueous electrolyte secondary battery to which the present invention is applied, any of those usually used in this type of non-aqueous electrolyte secondary battery can be used. is there.

Examples of the negative electrode active material include carbonaceous materials, lithium and lithium alloys. As a concrete example, as the carbonaceous material, lithium is doped,
Organic materials that can be dedoped and that are obtained by firing pyrolytic carbons, pitch cokes, needle cokes, petroleum cokes, cokes, graphites, glassy carbons, phenolic resins, furan resins, etc. at an appropriate temperature. Examples include fired bodies of polymer compounds, carbon fibers, activated carbon and the like.

As the lithium alloy, Li-Al, Li
An alloy such as -Sn or Li-Pb may be used.

On the other hand, as the electrolytic solution, any conventionally known electrolytic solution can be used as long as the electrolytic solution is dissolved in an organic solvent.

Therefore, as the organic solvent, esters, diethyl ether, tetrahydrofuran, substituted tetrahydrofuran, dioxolane, pyran and its derivatives, ethers such as dimethoxyethane and diethoxyentane, and 3-methyl-2-oxazolidinone are used. 3-substituted-2-oxazolidinones, sulfolane, methylsulfolane, acetonitrile, propionitrile, etc. are used, and these may be used alone or as a mixture of two or more kinds.

As the electrolyte dissolved in the above organic solvent, lithium perchlorate, lithium borofluoride, lithium phosphorofluoride, lithium chloroaluminate, lithium halide, lithium trifluoromethanesulfonate and the like can be used.

Further, the above description is an example of the battery in which the negative electrode lead plate is welded to the inner bottom surface of the battery can and the positive electrode lead plate is welded to the battery lid. On the contrary, the positive electrode lead plate is The present invention can be applied to a battery having a structure in which the bottom surface of the inside of the battery can is welded and the positive electrode lead plate is welded to the battery lid, and the same operational effects are exhibited. That is, in such a battery,
A plurality of protrusions are provided on the portion of the positive electrode lead plate that is welded to the bottom surface of the inside of the battery can. As a result, the positive electrode lead plate and the inner bottom surface of the battery can are welded with the plurality of protrusions as welding points, so that the torsional strength and the tensile strength are strong, and the breakage resistance is excellent against vibration during carrying. Indicates.

[0028]

In the battery in which the positive electrode and the negative electrode are housed in the battery can and one of the lead plates connected to the positive electrode and the negative electrode is welded to the inner surface of the battery can, the battery can having the lead plate welded to the inner surface of the battery can When a plurality of protrusions are provided on the portion to be welded to the inner surface, the lead plate and the inner surface of the battery can are welded with the plurality of protrusions as welding points, which is a so-called multi-point welded form.

Therefore, compared with the case where the bottom surface of the battery can and the surface of the negative electrode lead plate are directly welded without interposing the protrusions, that is, when the flat surfaces are welded at one point, both the torsional strength and the tensile strength are higher. It is improved and exhibits excellent fracture resistance against vibration when the battery is used for portable use.

[0030]

EXAMPLES Examples to which the present invention is applied will be described in detail below based on concrete experimental results.

Example 1 First, the positive electrode plate 1 was manufactured as follows. LiMoO ₂ was produced by mixing 1 mol of lithium carbonate and 1 mol of cobalt carbonate and firing in air at 900 ° C. for 5 hours, and this LiCoO ₂ was crushed with a bowl mill to obtain a positive electrode active material.

Next, 91 parts by weight of the crushed LiCoO ₂ , 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder were mixed, and N-methylpyrrolidone as a dispersant was further mixed. Was added to prepare a positive electrode active material paste. The positive electrode active material paste is uniformly applied on both sides of a 30 μm thick aluminum foil current collector, dried, and then roller pressed to obtain
A positive electrode plate 1 was produced. The positive plate has a width of 35 m.
m is a plate-like body having a length of 300 mm and a thickness of 0.18 mm.

A nickel positive electrode lead plate 7 having a width of 4 mm was attached to the end of the positive electrode plate thus manufactured by welding.

Next, the negative electrode plate 2 was produced as follows. Pitch coke was ground in a vibrating mill for 2 minutes with 12.7 mm diameter stainless steel balls. This crushed pitch coke has a true density of 2.03 g / cm ³ , 00.
The spacing between the two surfaces was 3.46Å, and the crystal thickness Lc in the C-axis direction was 40Å. The spacing between the 002 planes was determined by X-ray analysis according to the Japan Society for the Promotion of Science. Next, 90 parts by weight of this granular pitch coke and 10 parts by weight of polyvinylidene fluoride serving as a binder were mixed, and N-methylpyrrolidone serving as a dispersant was further added to prepare a negative electrode active material paste.

Then, as shown in FIG. 2, the negative electrode pastes 6a and 6b are evenly applied to both surfaces of the copper foil current collector 5 having a thickness of 10 μm, dried, and then subjected to roller pressing to obtain a negative electrode plate. 2 was produced. In addition, this negative electrode plate 2
Is a plate-like body having a width of 35 mm, a length of 300 mm and a thickness of 0.2 mm.

A nickel negative electrode lead plate 8 having a width of 4 mm and a thickness a of 0.1 mm is attached to the end of the negative electrode plate 2 by welding, and a portion of the negative electrode lead plate 8 to be welded to the inner surface of the battery can. 3 and 4, hemispherical projections 11 having three rows in the width direction and four rows in the longitudinal direction were formed by press working. The protrusions had a height b of 0.3 mm, a protrusion interval c of 1.25 mm, and a distance d from the end of the lead plate.
Was formed at a position of 1.75 mm.

Next, the positive electrode plate 1 to which the positive electrode lead plate 7 is welded and the negative electrode plate 2 to which the negative electrode lead plate 8 are welded are combined into a pair of thin plate separators 3a, 3b made of polypropylene.
The negative electrode plate 2, the separator 3a, the positive electrode plate 1, and the separator 3b were laminated in this order, and the spirally wound electrode body 12 was produced by winding the laminated body in a spiral form. The spiral electrode body 12 was housed in a nickel-plated iron can 4.

Then, the positive electrode lead plate 7 was welded to the battery lid 9 and the negative electrode lead plate 8 was welded to the inner bottom surface of the battery can 4. The negative electrode lead plate 8 was welded to the inner bottom surface of the battery can 4 by using a pair of resistance welding electrodes and locally passing an electric current to the portion to be welded. That is, first, as shown in FIG. 5, the position of the negative electrode lead plate 8 was adjusted so that the projection 11 of the negative electrode lead plate 8 was located in the substantially central region of the bottom surface of the battery can 4. Next, the battery can 4 is placed on the resistance welding electrode 31a so that the bottom surface is on the side of the electrode 31a, and the rod-shaped resistance welding electrode 31b is further inserted into the center of the spirally wound electrode body 12 so that the tip thereof is Welding was performed by contacting the negative electrode lead plate 8 and applying a current between the resistance welding electrodes 31a and 31b.

After the positive electrode lead plate 7 and the negative electrode lead plate 8 are welded in this way, 1 mol of lithium hexafluorophosphate is added to a mixed solvent prepared by mixing carbon propylene and diethyl carbonate in the battery can 4. The dissolved electrolytic solution was injected at a ratio of 1. Then, the polypropylene gasket 9 and the battery lid 10 are inserted into the upper part of the battery can 4, and the upper part of the battery can 4 is caulked to seal the battery can.
A 000-cell non-aqueous electrolyte secondary battery (Example battery 1) was prepared. The non-aqueous electrolyte secondary battery had an outer diameter of 13.
It has a cylindrical shape of 8 mm and a height of 45 mm.

Comparative Example 1 A non-aqueous electrolyte secondary battery (Comparative Example Battery 1) was prepared in the same manner as in Example 1 except that no protrusion was formed on the negative electrode lead plate.
00 cells were created.

Each battery thus prepared was charged for 8 hours under the conditions of a charging voltage of 4.2 Vmax and a current of 100 mA, and after charging, the internal resistance to an alternating current of 1 kHz was measured. Further, the battery whose internal resistance was measured in this manner was freely dropped three times in any direction from the height position of 1 m onto concrete, and the internal resistance was measured in the same manner.

Table 1 shows the number of batteries of the example batteries and the comparative example batteries whose internal resistance increased due to dropping.

[0043]

[Table 1]

As can be seen from Table 1, in the comparative battery in which the negative electrode lead plate and the inner bottom surface of the battery can are welded without interposing the protrusions, 12 out of 1000 batteries increase in internal resistance. You It is considered that the increase in the internal resistance of these batteries is caused by the fact that the welding between the negative electrode lead plate and the inner bottom surface of the battery can was destroyed by dropping. On the contrary,
In the example battery in which the negative electrode lead plate and the inner bottom surface of the battery can were welded together through the protrusion, no battery having an increase in internal resistance was confirmed, and the welding between the negative electrode lead plate and the inner bottom surface of the battery can was destroyed. It turns out to be difficult.

Further, each battery was disassembled and the lead plate was twisted, and the torsional load force required for the lead plate to peel from the battery can was measured. The results are shown in Table 2.

[0046]

[Table 2]

As can be seen from Table 2, in the comparative example battery, the lead plate is peeled off by a torsional load of about 0.3 kg weight, whereas in the example battery, the lead plate is peeled off by 1.5 kg weight. And required a large torsion load force. In the above-mentioned example battery, the lead plate is provided with 12 protrusions and welded to the inner bottom surface of the battery can. However, even when 3 to 11 protrusions are provided on the lead plate and welded to the inner bottom surface of the battery can, the lead plate is also welded. The same level of torsional load force was required to peel off.

Therefore, providing the projection on the portion of the positive electrode lead plate to be welded to the bottom surface of the inside of the battery can improves the welding strength between the positive electrode lead plate and the bottom surface of the inside of the battery can, and can withstand external impact. It was found to be effective in obtaining a battery.

[0049]

As is apparent from the above description, in the present invention, the positive electrode and the negative electrode are housed in the battery can, and either the lead plate connected to the current collector of the positive electrode or the negative electrode is the inner surface of the battery can. In a battery that is welded to a battery, since a plurality of protrusions are provided on the welded portion of the lead plate to the inner surface of the battery can, it is possible to improve the welding strength between the lead plate and the inner bottom surface of the battery can of the battery having the above configuration. Is. Therefore, the welding of the lead plate and the inner surface of the battery can hardly breaks due to vibration during portable use, and it is possible to obtain a practical battery as a power source for portable equipment.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an essential part showing a configuration example of a battery to which the present invention is applied.

FIG. 2 is a schematic perspective view showing the configuration of a negative electrode plate.

FIG. 3 is a plan view showing an example of forming a protrusion formed on a lead plate.

FIG. 4 is a side view of the protrusion shown in FIG.

FIG. 5 is a schematic cross-sectional view showing a welding process of the lead plate and the inner surface of the battery can.

FIG. 6 is a schematic cross-sectional view showing the structure of a conventional battery.

[Explanation of symbols]

1 ... Positive electrode plate 2 ... Negative electrode plate 3a, 3b ... Separator 4 ... Battery can 5 ... Negative electrode current collector 6a, 6b ... Negative electrode active material paste 7: Positive electrode lead plate 8 ・ ・ ・ Negative electrode lead plate 9 ... Gasket 10 ... Battery lid 11 ... Protrusion

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshinari Ichise 1-1, Shimosugishita, Takakura, Hiwata-cho, Koriyama-shi, Fukushima Prefecture Sony Energy Tech Co., Ltd. Koriyama Plant (72) Hidenori Sato Koriyama-shi, Fukushima Prefecture 1-1, Shimo-Sugishita, Takakura, Hiwada-cho Sony Energy Tech Co., Ltd., Koriyama Plant (56) Reference JP-A-3-276560 (JP, A) JP-A-52-155336 (JP, A) 63-112762 (JP, U) Actual development Sho 62-167367 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 2/22

Claims (4)

(57) [Claims] 1. A positive electrode active material for both of an aluminum foil current collector.
A positive electrode plate applied to the surface, a metal positive electrode lead plate welded to the end portion of the positive electrode plate, a negative electrode plate applied to both surfaces of a copper foil current collector, the negative electrode plate, the end of the negative electrode plate The negative electrode lead plate made of metal welded to the part, and the positive electrode plate and the negative electrode plate laminated via the separator.
It has a battery can that contains the spirally wound electrode body.
However , the positive electrode lead plate or the negative electrode lead plate is inside the battery can.
A plurality of hemispherical protrusions arranged at a predetermined interval on the connection part with the surface
Is provided, and the hemispherical protrusion is welded to the inner surface of the battery can.
A battery characterized in that 2. The battery according to claim 1, wherein the plurality of protrusions provided on the welded portion of the lead plate are protrusions formed by press working. 3. The negative electrode active material applied to the negative electrode plate
Contains a carbonaceous material and uses an organic solvent as the electrolyte
A non-aqueous electrolyte secondary battery, characterized in that
Batteries on board. 4. The positive electrode active material coated on the positive electrode plate
Non-water containing lithium-cobalt composite oxide material
The electrolyte secondary battery according to claim 1, wherein the secondary battery is an electrolyte secondary battery.
battery.