JP3200130B2 - Prevention method for internal short circuit of electrode group for secondary 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 method for preventing an internal short circuit in a group of electrodes for a secondary battery.

[0002]

2. Description of the Related Art Conventionally, lead batteries, Ni / Cd
Batteries, lithium secondary batteries, etc. are used, but these dendrites cause internal short circuits on the upper and lower edges of the separator between the negative and anode plates due to the growth and falling off of dendrites generated by repeated charging and discharging. Therefore, various devices have been proposed. Among the various devices, as described in Japanese Patent Application Laid-Open No. 1-122574, it is basically assumed that when dendrite is generated, it is basically prevented by a separator. A separator having a width wider than these electrode plates is formed by projecting upper and lower edges thereof outward from upper and lower edges of the anode plate and the cathode plate, respectively, to form a wound electrode group having an upper protruding edge and a lower protruding edge. Each of the upper and lower protruding edges of the wound separator is bent in the direction of the core of the electrode plate group, and the bent edge and the lower edge of the inner separator are thermally fused by hot air. Means have been proposed to prevent the internal short-circuit of the electrode group by closing each of the upper surface open portion and the lower surface open portion between these adjacent edges.

[0003]

The above-described conventional means for preventing internal short-circuiting of the electrode group requires a step of bending the upper and lower projecting edges of the wound separator in the direction of the core of the electrode group, which is cumbersome. In addition, it takes a long time, and each of the heat-sealing operations is troublesome. In addition, when hot air is used for the heat-sealing, the hot-air hits the electrode plate group, and has a drawback such as a possibility of having an adverse effect. There are inconveniences.

[0004]

The present invention SUMMARY OF THE INVENTION is to solve the conventional problems described above, the simple and favorably it is possible to perform the upper and lower surfaces opening sealing of between separators adjacent the electrode plate group
In both cases , high efficiency and good prevention of internal short circuit of the electrode group
At the same time, the electrode group thus
So that the rechargeable batteries installed in the pond can be obtained all at once.
It was intended to provide a electrode plate group of the internal short-circuit prevention method for a secondary battery, the anode plate and the cathode plate and the cathode plate and these anode plate and the upper and lower edges than the wide thermoplastic resin separator these plates the respective of projecting outward from upper and lower edges constitute a plate group to comprise an upper projecting edge and a lower projecting edge, the ultra plate group, of the separator protruding at its upper and lower surfaces the <br/> upper projecting edge and the said lower protruding edge, folding these edges
Without bending Ri, housed in the battery container the <br/> each surface of the upper insulating sheet and the lower insulating sheet in a state of contact against each other
And performs laser irradiation from above and below of the battery container, that the formation of the sealing portion by welding these mutual abutment with each other
It shall be the feature.

[0005]

[Action] to the upper projecting edge and the lower projecting edge of the cell <br/> separator to Oite projecting upper surface and the lower surface of the polar plate group, these folding
The surfaces of the upper insulating sheet and the lower insulating sheet are brought into contact with each other without bending , so that it is simple and highly efficient.
Mutual contact work is obtained. This is stored in a battery container.
When irradiating the laser from above and below the battery container in the state,
The above-mentioned mutual
A good heat-sealing seal at the contact area is obtained, and thus the electrode group
That dendrite generated in the electrode plate is prevented from coming into contact with the opposite polarity plates of adjacent electrode plate group that is internally short-circuit prevention
At the same time as the
A good quality secondary battery provided in the container can be obtained at a stroke .

[0006]

Next, an embodiment of the present invention will be described. 1 to 3 show one embodiment of the present invention. In the drawing, reference numeral 1 denotes a wound electrode group for a lithium secondary battery. The electrode group 1 is mainly composed of a positive electrode active material such as manganese dioxide, and a conductive powder and a binder are mixed at an appropriate mixing ratio. A positive electrode mixture formed by pressing the positive electrode mixture formed on a stainless steel expanded metal current collector plate, a negative electrode plate 3 made of metallic lithium, and a positive electrode plate 2 interposed between the positive and negative electrode plates 2 and 3; It is made of a thermoplastic strip separator 4 such as a porous film made of polypropylene or the like wider than these electrode plates. Further, the upper and lower edges of the separator 4 are formed on the upper and lower ends of the anode and anode plates 2 and 4, respectively. Upper protruding edge 4a protruding outward from the edge and lower edge
And a lower protruding edge 4b. These laminates are spirally wound. Therefore, on the upper and lower surfaces of the wound electrode plate group 1,
The upper projecting edges 4a, 4a,... And the lower projecting edges 4b, 4b,... Of the spiral separator 4 are arranged in a plurality of layers at predetermined intervals in the radial direction. Thus, between each adjacent upper protruding edge 4a, and between each adjacent lower protruding edge 4a.
A wound electrode plate group 1 having a configuration in which a top open part 5a and a bottom open part 5b composed of a spiral space are formed in a plurality of layers in the radial direction between b and 4b. There is no difference from the wound electrode group.

According to the invention, the upper projecting edge 4a to Oite respectively protrude on the upper surface and the lower surface of the wound electrode plate group 1, 4a, ...
And the lower protruding edges 4b, 4b,... As shown in FIG.
Surfaces of the thermoplastic of the upper insulating sheet 6 and the lower insulating Sea 7 without bending the edges of these respectively abut. That is,
As shown in FIG. 1, the inner surface of the upper insulating sheet 6 and the upper protruding edges 4a, 4a,... Of the electrode plate group 1 are brought into contact with each other, and at the same time, the respective upper surface open portions 5a, 5a, , And the inner surface of the lower insulating sheet 7 and the lower protruding edges 4b, 4b,... Of the electrode plate group 1 are brought into contact with each other, and at the same time, the respective lower surface open portions 5b, 5b,. ... is covered and closed. These insulating sheets 6 and 7 are made of the same material as the separator in the illustrated example. Furthermore, the present invention
With it, as in the illustrated embodiment, the wound electrode plate group 1 provided with the Such upper insulating sheet 6 and the lower insulating sheet 7, accommodated in a cylindrical metallic battery case 8, on its upper surface, A metal lid plate 9 was provided, and the peripheral edge was integrally welded to the rim of the battery container 8. The metal cover plate 9 has an opening 10 for injecting an electrolytic solution at the center thereof, and an inner peripheral surface of a cylindrical glass hermetic seal member 11 bonded to the inner peripheral surface of the circular rim in a gas-liquid tight manner. the electrodeposition of a cylindrical metal terminal 12 which made dressed forming a gas-liquid-tight
Create in advance in the pond .

According to the present invention, the battery container 8 of such a battery is provided.
When applying laser irradiation to the outer surface of the lid plate 9 and the outer surface of the bottom wall of the container 8 from above and below the surface areas A and B as shown by phantom lines in FIG. 2 and FIG. 6 and all of the mutual contact portions of the upper projecting edges 4a, 4a,... And all of the mutual contact portions of the lower insulating sheet 7 and the lower projecting edges 4b, 4b,. The upper seal connecting parts 13a, 13a, ... and the lower seal parts 13b, 13b,
... is obtained. Thus, the upper insulating sheet 6 and the lower insulating sheet 7 are fixed to the upper protruding edges 4a, 4a,... And the lower protruding edges 4b, 4b,. Each top opening 5a, 5a,
, And the upper surface open portions 5b, 5b,... By the fixed lower insulating sheet 7 are obtained. Incidentally, no heat deformation of the battery container and the cover plate was observed at all by the heating by the laser irradiation. In the drawing, reference numeral 14 denotes an anode lead plate which is led out of the positive electrode plate 2 and connected to the annular terminal member 12;
Is a cathode lead plate led out of the negative electrode plate 3 and connected to the inner surface of the bottom wall of the container 8, 16 is a through hole provided in the center of the upper insulating sheet 6, and 17 is provided in the center of the lower insulating sheet 7. FIG.

After the above heat welding process by laser irradiation, a predetermined amount of electrolyte is injected from the electrolyte injection opening 10, that is, the opening 10 at the center of the cylindrical terminal 13. A metal plug member 18 such as a metal pin material for sealing is fitted, and the outer surface thereof is irradiated with a laser to perform a welding seal between the plug member 18 and the terminal 13, thereby obtaining the electrode plate of the present invention. A sealed cylindrical lithium secondary battery provided with the upper and lower openings of the group is sealed.

Even if the battery constructed as described above is repeatedly charged and discharged and lithium dendrite is generated on the negative electrode plate 3 and grows or falls off, as described above, the electrode plate group 1 keeps the upper part welded thereto. , And the lower openings 5b, 5b,... Are closed by the lower insulating sheets 6, 7, so that the dendrite is confined therein and prevented from moving to the adjacent positive electrode plate 2. Therefore, the internal short circuit of the electrode plate group 1 due to the lithium dendrite is prevented, and a long-life battery is obtained.

A large number of the above-mentioned batteries were prepared, and their life tests were performed as follows. That is, a cycle test was performed at a current density per unit area of 0.3 mA / cm ² , a discharge end voltage of 2 V, a charge end voltage of 3.8 V, and an environmental temperature of 25 ° C.
The cycle end was judged to be the life of the battery when it became 50% or less of the initial discharge capacity. In addition, during charging, the case where the voltage dropped by 10 mV from the maximum voltage in that cycle was determined to be an internal short circuit, and the test was terminated. For comparison, a number of conventional cylindrical lithium secondary batteries having the same configuration except that the upper insulating sheet and the lower insulating sheet were not provided, that is, a plurality of conventional cylindrical lithium secondary batteries were manufactured, and the same life test as above was performed, and an internal short circuit was performed. Was checked for its presence.

The results are as shown in FIG. In the drawing, the normal cycle life of the battery is indicated by ○, and the cycle life due to short circuit is indicated by △. As is clear from the drawing,
In the battery according to the present invention, no internal short circuit occurred.
In contrast, most of the conventional batteries have an internal short circuit.

[0013] The internal short circuit Prevention Act electrode plate assembly of the present invention shown in FIG. 1 were laser irradiation after accommodated in the battery container
, And the upper projecting edges 4a, 4a,.
The outer edges 4b, 4b ,.
Preparative 6 and the welded sealing binder of the lower insulating sheet 7 is obtained
At the same time, the electrode plate group 1 with internal short circuit prevented by this
A good secondary battery is obtained. Further, in the above embodiment, the case where the present invention is applied to the wound electrode group is shown, but the present invention can also be applied to a plane electrode group in which a plurality of positive electrode plates, a negative electrode plate, and a plurality of separators are stacked. .

[0014]

As described above, according to the present invention, the upper edge and the lower edge of the separator interposed between the upper and lower edges of the positive electrode plate and the negative electrode plate and wider than these electrode plates are respectively connected to the anode plate and the anode plate. upper and lower ends upper projecting edge and said lower projecting end of said separator construction the electrode assembly to include a <br/> upper projecting edge and the lower projecting edge which is projected outwardly from the edge of the cathode plate
Top insulation without bending these protruding edges to the edges
Since the respective inner surfaces of the sheet and the lower insulating sheet is brought into contact with each other, eliminating the tedious task to fold the conventional protruding edge
Can perform mutual contact work in a short time
You. Further, the electrode groups in such a state that they are in contact with each other are electrically charged.
Housed in a pond container and irradiate laser from above and below the battery container
So that these mutual contact parts are welded to each other by heating.
The hot plate, as in the past, adversely affected the plates
Not only eliminates inconvenience, but also smooth and efficient
In addition, heat sealing of these mutual contact portions can be performed,
This has the effect of preventing internal shorting of the electrode
A high-quality electrode group with internal short-circuit prevention
Battery Bei the good quality has the effect of such obtained at once.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical lithium secondary battery to which an embodiment of the present invention is applied.

FIG. 2 is a top view of the battery shown in FIG.

FIG. 3 is a bottom view thereof.

FIG. 4 shows a comparison graph of a charge / discharge cycle test of the battery of the present invention and a conventional battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electrode group 2 Positive electrode plate 3 Negative electrode plate 4 Separator 4a Upper protruding edge of separator 4b Lower protruding edge of separator 5a Upper opening 5b Lower opening 6 Upper insulating sheet 7 Lower insulating sheet 8 Battery container 9 Cover plate 13a Upper part Seal binding part 13b Lower seal binding part

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 10/00-10/40

Claims (1)

(57) [Claims] 1. An anode plate and a cathode plate which are made of a thermoplastic resin separator wider than these electrode plates and whose upper and lower edges are projected outward from upper and lower edges of the anode plate and the cathode plate, respectively. An electrode group having an edge and a lower projecting edge, and the electrode group protruding from upper and lower surfaces thereof.
To the upper projecting edge of the regulator and the said lower protruding edge, these
Without bending the edge, the battery capacity of the surface of each of the upper insulating sheet and the lower insulating sheet in a state of contact against each other
It is housed in a container, and laser irradiation is performed from above and below the battery container.
There, an internal short circuit prevention method of the secondary battery plate groups you characterized in that by welding these mutual abutment with each other to form <br/> the seal portion.