KR100731461B1 - Lithium secondary battery - Google Patents

Abstract

The present invention relates to a lithium secondary battery, comprising: an electrode assembly having two electrodes having different polarities and a separator interposed between the two electrodes; A can accommodating the electrode assembly therein and having a support portion at a central side of a long side; And a cap assembly including a cap plate sealingly bonded to the can and an insulating member inserted into the cap plate, the cap assembly including a terminal having a polarity different from that of the can, wherein the support portion is formed to have a thick thickness of the can. Since the side is formed in the center in the longitudinal direction at both sides having a long side, it is effective to maximize the stability of the battery by suppressing the swelling phenomenon generated during abnormal charging of the battery.

Lithium Secondary Battery, Can, Support

Description

Lithium secondary battery {Lithium secondary battery}

1 is a perspective view of a lithium secondary battery according to an embodiment of the present invention.

Figure 2 is an exploded perspective view of Figure 1;

3 is a cross-sectional view taken along line III-III of FIG. 1;

4 is a cross-sectional view of a can according to another embodiment of the present invention.

5 is a cross-sectional view of a can according to another embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

100; Lithium secondary battery 110; Electrode assembly

111; Anode plate 112; Negative plate

113; Separator 120; Cans

121; Long side flank 122; Short side

123; 124; Top opening

125; Support 140; Cap assembly

The present invention relates to a lithium ion secondary battery, and more particularly, to a lithium ion secondary battery capable of suppressing swelling of the battery and improving safety.

In general, a lithium ion secondary battery is a cathode electrode plate with a positive electrode active material, a negative electrode plate with a negative electrode active material, and a separator that is located between the positive electrode plate and the negative electrode plate to prevent shorts and to allow only lithium ions to move. An electrode assembly wound in the form of a jelly roll, a can to which the electrode assembly is coupled, a cap assembly that blocks the can to prevent the electrode assembly from being separated, and is injected into the can to allow lithium ions to move. It consists of electrolyte solution etc.

The lithium ion secondary battery is laminated with a positive electrode plate with a positive electrode active material, a negative electrode plate with a negative electrode active material and a separator, and then wound in a jelly roll form, put it in a rectangular can, and then The cap assembly is sealed by welding.

Subsequently, after the electrolyte is injected, charging and inspection are performed to complete a bare cell. Then, various safety devices are attached to the bare cell and then assembled and inspected to complete a normal battery pack.

On the other hand, since the lithium ion secondary battery uses the constant voltage / constant current charging method, if the charging voltage is accurately controlled in the charger, there is no overcharge phenomenon. However, the charger may be damaged or malfunction, causing abnormal charging. In this case, the battery voltage continues to increase due to the characteristic of the potential of the positive electrode active material, for example, lithium cobalt sulfate (LiCoO ₂ ), constantly rising, and An abnormal heating phenomenon occurs.

As a safety measure against this phenomenon, a separator with a PTC (Positive Temperature Coefficiency) element may be incorporated or a shut down function may be adopted. In addition, a safety vent operated by gas generation may be provided. Can be. Here, the safety side of the lithium ion secondary battery generally refers to a thinner area formed on the bottom surface or the cap assembly of the can, which is ruptured when swelling is severe due to gas generation and serves to discharge the gas.

The gas is generated by using lithium carbonate (Li 2 CO ₃ ) to form a positive electrode active material such as lithium cobalt (LiCoO ₂ ), which is added in excess of stoichiometry. That is, the lithium carbonate added by the overheating remains in the lithium cobalate as a positive electrode active material in an unreacted state, but the battery voltage becomes high due to abnormal charging, and when the heat is generated, lithium carbonate is decomposed to generate carbon dioxide gas. Due to the generation of carbonic acid gas, a swelling phenomenon in which the can is normally inflated occurs, and when the swelling phenomenon is severe, the safety valve operates.

This swelling phenomenon is solved by adding less lithium carbonate. However, in this case, cobalt oxide (CoO ₂ ) remains in the positive electrode active material, so that the positive electrode is corroded and eluted into the electrolyte during charging, which causes cobalt precipitation to the negative electrode. By inducing a greater risk of internal shorts, it is inevitable to overload lithium carbonate. In addition, the swelling phenomenon is caused by various causes such as the electrode assembly is expanded while the volume of the active material of the electrode is changed by the charge and discharge of the battery.

In the swelling phenomenon, the vicinity of the center of the side of the short side of the can is mainly contracted inward, and the center of the side of the long side is excessively inflated outward. At this time, the amount of shrinkage on the side of the can short side is negligible, but the amount of expansion on the side of the long side will cause deterioration of the battery performance.

An object of the present invention devised in view of the above problems is to provide a lithium secondary battery that can improve the safety of the battery by suppressing the swelling phenomenon occurring excessively in the center of the side of the battery.

According to an aspect of the present invention, a lithium secondary battery includes: an electrode assembly including two electrodes having different polarities and a separator interposed between the two electrodes; A can accommodating the electrode assembly therein and having a support at a center of a side of a long side; And a cap assembly including a cap plate sealingly bonded to the can and an insulating member inserted into the cap plate, the cap assembly including a terminal having a polarity different from that of the can.

The support is made of a thick can of the can. The support is formed on both sides having the long sides of the rectangular can, and is formed in the longitudinal direction at the can side.

The support portion is formed in the range of 30 to 50% of the total can side volume, the support portion is formed thicker in the range of 10 to 30% than the left and right portions at the center of the side having a long side, the width in the length direction is It is formed in 1/3 or more.

The support may be formed to be recessed inwardly of the can or protrude outward of the can, and at the same time, may be formed to protrude outwardly while being recessed inwardly.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that those skilled in the art may easily implement the present invention.

1 is a perspective view of a lithium ion secondary battery 100 according to an embodiment of the present invention, Figure 2 is an exploded perspective view of the lithium ion secondary battery 100 of FIG.

As shown in Figure 1 and 2, the lithium ion secondary battery according to an embodiment of the present invention is an electrode assembly 110 for generating a voltage difference, and a rectangular parallelepiped having the upper opening is formed by receiving the electrode assembly 110 Can 120, a cap assembly 140 assembled at an upper opening of the can 120 to prevent the electrode assembly 110 from being separated, and injected into the can 120 to form an electrode assembly 110. It consists of an electrolyte solution that enables ion migration in the liver.

The electrode assembly 110 is positioned between the positive electrode plate 111 attached to the positive electrode active material, the negative electrode plate 112 attached to the negative electrode active material, and the positive electrode plate 111 and the negative electrode plate 112 to prevent a short and only move lithium ions. The separator 113, and the positive electrode plate 111, the negative electrode plate 112, and the separator 113 are wound in a jelly roll shape and accommodated in the can 120. Here, the positive electrode plate 111 may be an aluminum (Al) foil, the negative electrode plate 112 may be a copper (Cu) foil, and the separator 113 may be polyethylene (PE) or polypropylene (PP). It does not limit the material. In addition, a positive electrode lead 114 protruding a certain length upward is welded to the positive electrode plate 111, and a negative electrode lead 115 protruding a predetermined length upwardly is welded to the negative electrode plate 112. The positive electrode lead 114 may be made of aluminum (Al) and the negative electrode lead 115 may be made of nickel (Al), but the present invention is not limited thereto.

The can 120 includes a side surface 121 having a long side facing each other, a side surface 122 and a bottom surface 123 having a short side, and formed in the shape of a rectangular parallelepiped having an opening 124 formed at an upper end thereof. The can 120 may be generally formed of aluminum (Al), iron (Fe), an alloy, or an equivalent thereof. The anode 120 may be welded to the can 120 to act as the anode 120. do.

As the electrode assembly 110, the insulating case 131, the terminal plate 132, and the insulating plate 133 are sequentially coupled to the upper portion of the can 120, and the insulating case 131 and the terminal plate 132 are combined. The insulating plate 133 has through holes 131a, 132a, and 133a, respectively, so that the negative electrode terminal 150 extends upward.

The cap assembly 140 is laser-welded to the can 120, which is provided with a substantially plate-shaped cap plate 141, and a through hole 141a having a predetermined size is formed in the center of the cap plate 141. An electrolyte injection hole 141b for injection of an electrolyte solution is formed at the side thereof. In addition, an insulating gasket 142 is coupled to the through hole 141a of the cap plate 141, and a negative electrode terminal 150 is coupled to the insulating gasket 142. Of course, the negative electrode terminal 150 is welded to the negative electrode lead 115 to serve as a negative electrode during discharge or charging. In addition, after the electrolyte is injected into the electrolyte injection hole 141b of the cap plate 141, the stopper 143 is coupled so that the electrolyte does not flow out.

On the other hand, the electrolytic solution (not shown) serves as a moving medium of lithium ions generated by the electrochemical reaction at the positive and negative electrodes inside the battery during charge and discharge, which is a non-aqueous organic electrolyte that is a mixture of lithium salts and high purity organic solvents. Can be. In addition, the electrolyte may be a polymer using a polymer electrolyte.

3 is a cross-sectional view taken along line III-III of FIG. 1, and as shown in FIG. 3, the can 120 of the lithium ion secondary battery 100 according to the present invention has swells on both sides 121 having long sides. The support 125 is formed by forming a thick can to suppress a ring phenomenon.

The support part 125 is formed in the longitudinal direction at the center of the side surface 121 having the long side of the can 120. The reason for forming the support part in the central portion of the side surface 121 is to suppress the phenomenon that the central portion of the side having the long side is expanded to the outside when the can swelling occurs.

The support 125 is formed to have a range of at least 30-50% in the volume of the side surface 121 having the long side in the can. Alternatively, the thickness of the support part 125 on the side surface 121 having a long side is formed to be thicker in the range of 10 to 30% than the thickness of the left and right portions where the support part 125 is not formed. That is, since the thickness of the can side 121 is usually 0.2 to 0.4 mm, the support part 125 has a thickness of about 0.23 to 0.25 mm when the minimum is 0.2 mm. At this time, the width direction length L2 of the support part 125 is formed to be 1/3 or more of the long side length L1 of the entire side surface.

In this way, the support 125 is formed to be thicker than the long side side 121, so that the thickness of the left and right sides of the support 125 formed in the center of the side surface 121 can be formed thinner than the normal thickness in consideration of the reduction in the capacity of the entire can. It may be. In this case, the anti-swing effect is obtained while the capacity of the battery is not reduced.

As shown in FIG. 3, the support part 125 according to an embodiment of the present invention is formed to protrude to the outside of the long side side 121 of the can 120. It is not.

That is, as another embodiment of the present invention, as shown in FIG. 4, the support part 125 may be formed to be recessed inward of the long side surface 121 of the can 120.

In addition, as shown in FIG. 5, the support part 125 may be formed in a shape that protrudes and recesses in and out of the long side side 121 of the can. However, in the case of the support 125, it should be formed in the same thickness range as in the above-described embodiment so as to be able to suppress the expansion of the long side side of the can during swelling.

The operation of the lithium secondary battery according to the present invention configured as described above will be described.

Due to the abnormal charging, the battery voltage becomes high, and a swelling phenomenon in which the can is excessively inflated is usually generated by generation of carbon dioxide gas generated when lithium carbonate is decomposed. Such swelling causes the can near the center of the short side to contract inward and the center of the long side to swell outwardly. Get mad.

However, in the lithium secondary battery according to the present invention, since the support portion 125 is formed in the longitudinal direction at the center of the side surface 121 having the long side of the can 120, the expansion of the long side side 121 is suppressed.

As described above, the lithium ion secondary battery according to the present invention has the effect of maximizing the stability of the battery by suppressing the swelling phenomenon caused when the can formed of a metal material is abnormally charged, particularly on the long side side.

The present invention is not limited to the above embodiments, and as claimed in the claims, to those skilled in the art to which the present invention pertains without departing from the gist of the present invention to the extent that various modifications can be made. It will be said that there is a technical spirit of the present invention.

Claims (9)

delete delete delete delete An electrode assembly having two electrodes having different polarities and a separator interposed between the two electrodes; A can in which the electrode assembly is accommodated therein and a support is formed at a central side of a long side of the electrode assembly; And a cap assembly including a cap plate sealingly bonded to the can and an insulating member inserted into the cap plate, the cap assembly including a terminal having a polarity different from that of the can. The support portion is a lithium secondary battery, characterized in that formed in the range of 30 to 50% of the side volume having the long side of the can. An electrode assembly having two electrodes having different polarities and a separator interposed between the two electrodes; A can in which the electrode assembly is accommodated therein and a support is formed at a central side of a long side of the electrode assembly; And a cap assembly including a cap plate sealingly bonded to the can and an insulating member inserted into the cap plate, the cap assembly including a terminal having a polarity different from that of the can. The support part is a lithium secondary battery, characterized in that formed in the center of the side having the long side of the can thicker than 10 to 30% range than the left and right portions. An electrode assembly having two electrodes having different polarities and a separator interposed between the two electrodes; A can in which the electrode assembly is accommodated therein and a support is formed at a central side of a long side of the electrode assembly; And a cap assembly including a cap plate sealingly bonded to the can and an insulating member inserted into the cap plate, the cap assembly including a terminal having a polarity different from that of the can. The width direction length (L2) of the support portion is a lithium secondary battery, characterized in that formed at least 1/3 of the long side length (L1) on the side of the can. delete An electrode assembly having two electrodes having different polarities and a separator interposed between the two electrodes; A can in which the electrode assembly is accommodated therein and a support is formed at a central side of a long side of the electrode assembly; And a cap assembly including a cap plate sealingly bonded to the can and an insulating member inserted into the cap plate, the cap assembly including a terminal having a polarity different from that of the can. The support part is a lithium secondary battery, characterized in that formed to protrude to the outside of the side having the long side of the can.

Images