KR20070071240A - Lithuim rechargeable battery - Google Patents

Abstract

Provided is a lithium secondary battery having improved productivity and capable of reducing in infiltration time of an electrolyte solution by making the internal surface of a case be rough. The lithium secondary battery comprises an electrode assembly; a sealing tape which is adhered to the outer circumference of the electrode assembly; a case which accommodates the electrode assembly; and a cap assembly which seals the upper aperture of the case, wherein a groove(350) is formed in intaglio at the internal surface of the case in which the case comes in contact with the electrode assembly. Preferably the groove is linearly formed along the surface of a post from the upper aperture of the case to the lower part.

Description

Lithium rechargeable battery

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

2 is a cross-sectional view taken along the line A-A of FIG.

Figure 3 is a cross-sectional view showing only the shape of the can before beading and crimping in Figure 2

Figure 4a is a cross-sectional view showing only the shape of the can of B-B cross-sectional view of FIG.

4B is a cross-sectional view of another embodiment of FIG. 4A.

4C is a cross-sectional view showing another embodiment of FIG. 4A

5A is a cross-sectional view showing another embodiment of FIG.

FIG. 5B is a sectional view of yet another embodiment of FIG. 5A

6 is a perspective view of an electrode assembly to which a PVdF coated sealing tape is attached according to an embodiment of the present invention.

FIG. 7 is a perspective view illustrating a shape in which the electrode assembly of FIG. 6 is inserted into the can of FIG. 5A.

<Description of Symbols for Main Parts of Drawings>

100-cylindrical lithium secondary battery 200-electrode assembly

215-Anode Tab 225-Anode Tab

250-sealing tape 300-can

310-side plates 330-crimping section

340-Beading section 350, 352, 354-Engraved groove

360-diagonal stripe 370-embossed

400-Cap Assembly 410-Safety Band

420-current blocking means (CID)

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having improved impregnation of an electrolyte by forming a recess or roughness on an inner surface of a case.

Secondary batteries are rechargeable and have a high possibility of being small and large in capacity. Recently, as demand for portable electronic devices such as camcorders, portable computers, and mobile phones is increasing, research and development on secondary batteries has been made with the power of these portable electronic devices. Representative examples of the recent development and use include nickel-hydrogen (Ni-MH) batteries, lithium (Li) ion batteries, and lithium ion (Li-ion) polymer batteries.

Lithium, which is widely used as a material for secondary batteries, is a material suitable for producing a battery having a large electric capacity per unit mass due to a small atomic weight of the element itself. On the other hand, since lithium reacts violently with moisture, a non-aqueous electrolyte is used in a lithium battery. In this case, since it is not affected by the electrolysis voltage of water, the lithium-based battery has an advantage of generating an electromotive force of about 3 to 4 volts.

The non-aqueous electrolyte used in the lithium secondary battery includes a liquid electrolyte and a solid electrolyte. The liquid electrolyte is obtained by dissociating a lithium salt into an organic solvent. As the organic solvent, ethylene carbonate, propylene carbonate or other alkyl group-containing carbonates or similar organic compounds can be used.

Typically, the lithium secondary battery is a separator that is positioned between the positive electrode plate coated with a positive electrode active material, the negative electrode plate coated with a negative electrode active material, and the positive electrode plate and the negative electrode plate to prevent a short and to allow only movement of lithium ions. And an electrode assembly wound around the electrode assembly, a case accommodating the electrode assembly, and an electrolyte solution injected into the case to enable movement of lithium ions.

On the other hand, a sealing tape is attached to the outer circumferential surface of the electrode assembly to support and protect the electrode assembly in a wound form. The sealing tape is usually made of a material such as polyethylene (PE), polypropylene (PP), and is not familiar with the electrolyte solution. In the case of a cylindrical battery and a square battery, the case is made of a metal can such as an aluminum alloy. Unlike the sealing tape, the inner surface of the can has a good affinity with the electrolyte.

When the electrode assembly is inserted into the case, the outer circumferential surface of the electrode assembly on which the sealing tape is wound is brought into close contact with the inner surface of the case. Accordingly, the sedimentation of the electrolyte is delayed due to the sealing tape having poor affinity with the electrolyte. In addition, the recent increase in the capacity of the battery increases the density of the electrode assembly, and the adhesion between the case and the sealing tape becomes more severe. In this situation, there is a need to change the shape of the inner surface of the case to increase the settling speed of the electrolyte.

The present invention is to solve the problems of the conventional lithium secondary battery described above, an object of the present invention is to provide a lithium secondary battery with improved impregnation of the electrolyte by forming a groove or roughness on the inner surface of the case.

Lithium secondary battery in one aspect of the present invention for achieving the above object, an electrode assembly, a sealing tape attached to the outer peripheral surface of the electrode assembly, a case for accommodating the electrode assembly, sealing the upper opening of the case In the lithium secondary battery comprising a cap assembly, it characterized in that the groove is formed on the inner surface of the case in which the case and the electrode assembly contact. At this time, the groove may be formed linearly along the column surface from the upper opening to the lower end of the case. In addition, the groove may have a cross-sectional shape in a direction parallel to the bottom surface of the case, any one of a triangle, a square, a semi-circular. In addition, the groove is preferably formed to a depth of 15% or less of the thickness of the case, the groove is preferably formed to a depth of 37.5㎛ or less.

In addition, the lithium secondary battery may have a cylindrical shape including a cap assembly having a safety vent. At this time, it is preferable that the case withstands a pressure three times or more of the operating pressure of the safety vane, and the case preferably withstands an internal pressure of 15 kg / m 2 or more.

In addition, the sealing tape may be coated with a material that is friendly to the electrolyte, and the material that is friendly to the electrolyte may be a polymer material. In this case, the polymer material may be PVdF 761.

In another aspect of the present invention, a lithium secondary battery includes an electrode assembly, a sealing tape attached to an outer circumferential surface of the electrode assembly, a case accommodating the electrode assembly, and a cap assembly sealing a top opening of the case. In the lithium secondary battery formed, the case is characterized in that the inner surface is formed rough (rough). At this time, the sealing tape may be formed by coating a material familiar with the electrolyte. In this case, the material friendly to the electrolyte may be a polymer material, and the polymer material may be polyvinyl difluoride (hereinafter referred to as PVdF) 761.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view of a cylindrical lithium secondary battery according to an exemplary embodiment of the present invention, and FIG. 2 is a sectional view taken along the line A-A of FIG. However, here, the description has been developed as a cylindrical lithium secondary battery for convenience, but of course, the present invention can be applied to the case of square and pouch-type lithium secondary batteries.

1 and 2, the cylindrical lithium secondary battery 100 includes an electrode assembly 200, a cylindrical can 300 containing the electrode assembly 200 and an electrolyte, and an upper portion of the cylindrical can 300. It is formed to include a cap assembly 400 for sealing the cylindrical can 300 to flow the current generated in the electrode assembly 200 to an external device.

Referring to FIG. 2, the electrode assembly 200 includes a positive electrode plate 210 coated with a positive electrode active material layer on a surface of a positive electrode current collector, a negative electrode plate 220 coated with a negative electrode active material layer on a surface of a negative electrode current collector, and the positive electrode plate. A separator 230 positioned between the 210 and the negative electrode plate 220 to electrically insulate the positive electrode plate 210 and the negative electrode plate 220 is wound and formed in a jelly-roll shape.

Although not shown in detail in the drawing, the positive electrode plate 210 includes a positive electrode current collector made of a thin metal plate having excellent conductivity, for example, aluminum (Al) foil, and a positive electrode active material layer coated on both surfaces thereof. have. Both ends of the positive electrode plate 210 are provided with a positive electrode current collector region, that is, a positive electrode non-coating portion, in which a positive electrode active material layer is not formed. One end of the positive electrode non-coating portion is generally formed of aluminum (Al), and the positive electrode tab 215 protruding a predetermined length to the upper portion of the electrode assembly 200 is bonded.

In addition, the negative electrode plate 220 includes a negative electrode current collector made of a conductive metal thin plate, for example, copper (Cu) or nickel (Ni) foil, and a negative electrode active material layer coated on both surfaces thereof. Both ends of the negative electrode plate 220 are provided with a negative electrode current collector region, that is, a negative electrode non-coating portion, in which a negative electrode active material layer is not formed. One end of the negative electrode non-coating portion is generally formed of nickel (Ni), and the negative electrode tab 225 protruding a predetermined length to the lower portion of the electrode assembly 200 is bonded. In addition, the upper and lower portions of the electrode assembly 200 may further include insulating plates 241 and 245 for preventing contact with the cap assembly 400 or the cylindrical can 300, respectively.

2, the cylindrical can 300 may include a cylindrical side plate 310 having a predetermined diameter and a cylindrical side plate 310 such that a predetermined space in which the cylindrical electrode assembly 200 can be accommodated is formed. It is formed to include a lower plate 320 to seal the lower portion, the upper portion of the cylindrical side plate 310 is an opening (開口) for inserting the electrode assembly 200. By bonding the negative electrode tab 225 of the electrode assembly 200 to the center of the lower plate 320 of the cylindrical can 300, the cylindrical can 300 itself serves as a negative electrode. In addition, the cylindrical can 300 is generally formed of aluminum (Al), iron (Fe) or an alloy thereof. In addition, the cylindrical can 300 is formed with a crimping portion 330 bent from the top to the top to press the upper portion of the cap assembly 400 coupled to the upper opening. In addition, the cylindrical can 300 is beaded inwardly to press the lower portion of the cap assembly 400 at a position spaced apart from the crimping portion 330 by a distance corresponding to the thickness of the cap assembly (beading) A portion 340 is further formed.

Referring to FIG. 3, an indented groove 350 is formed on the inner surface of the can. FIG. 3 is a cross-sectional view of only a can in FIG. 2 and shows a shape before crimping and beading. Into the inside of the can 300 into which the electrode assembly 200 is inserted, an electrolyte that is a movement path of lithium ions is injected. 6, a sealing tape 250 is attached to the outer circumferential surface of the electrode assembly 200 to support and protect the electrode assembly 200. At this time, the inner surface of the can 300 is made of a material having a relatively good affinity with the electrolyte, such as aluminum, iron, the sealing tape 250 has a good affinity with the electrolyte, such as polyethylene (PE), polypropylene (PP). It is not made of material. In addition, when the electrode assembly 200 wound up is inserted into the can 300, the sealing tape 250 and the inner surface of the can 300 are closely adhered to each other, and there is little space for the electrolyte solution to settle. The sealing tape 250 is not intimate with the electrolyte solution, thereby preventing the electrolyte solution from penetrating by the capillary phenomenon.

In the present invention, an intaglio groove is linearly formed from the upper opening to the lower end on the inner surface of the can 300. 4A, 4B, and 4C, the intaglio grooves 350, 352, and 354 may be formed in one of a triangle, a quadrangle, and a semicircle. However, the shape of the cross section is not limited thereto, and other shapes may be used as long as the electrolyte can settle along the intaglio grooves 350, 352, and 354. When the intaglio grooves 350, 352, and 354 are formed in the side plate 310 of the can, the surface area of the can that is intimate with the electrolyte is enlarged relative to the sealing tape 250, so that the electrolyte may settle.

As described above, when the intaglio groove 350 is formed in the side plate 310 of the can, there is a problem that the electrolyte is advantageous to settle, but the strength is reduced in the portion where the intaglio groove 350 is formed. When the voltage of the battery rises above a certain limit due to overcharging or the like, or when the temperature inside the battery rises above a certain limit, gas is generated in the battery together with evaporation of the electrolyte. The gas generated as described above, with reference to FIG. 1, deforms or breaks the safety vent 410 to deform or break the current interruption means CID 420 located above the safety vent 410. When the current blocking means 420 is deformed or broken, the current is cut off and the phenomenon such as overcharging is stopped.

Therefore, the side plate 310 of the can should not be deformed or broken by the intaglio groove 350 until at least the safety vent 410 is operated due to the gas generated inside the battery. According to the results of experiments to increase the stability of the battery, the depth of the intaglio groove 350 is preferably formed to be less than 15% of the thickness of the side plate 310 of the can. Because, when the depth of the intaglio groove 350 exceeds 15% of the thickness of the side plate 310 of the can, the current blocking means 420 is deformed or broken due to the deformation of the safety vent 410, resulting in an overcharge state. This is because the side plate 310 of the can is deformed before it is completely stopped. Since the thickness of the cylindrical can is typically about 250 μm, the depth of the intaglio groove is preferably within 37.5 μm, which is 15% of 250 μm.

In addition, according to the results of experiments to increase the safety of the battery, the can 300 must withstand a pressure of at least three times the internal pressure of the battery in which the safety vent 410 operates. Typically, since the battery internal pressure at which the safety vent 410 starts to be deformed is in the range of 5 to 11 kg / m 2, the can 300 may have at least 15 kg / w even if the recess groove 350 is formed in the side plate 310. It must be able to withstand the pressure of ㎡.

According to another aspect of the present invention, a lithium secondary battery comprising an electrode assembly, a sealing tape attached to an outer circumferential surface of the electrode assembly, a case accommodating the electrode assembly, and a cap assembly sealing an upper opening of the case. The case is characterized in that the inner surface is rough (rough). The inner surface of the case is usually smoothly formed. Instead of such a smooth surface, it is necessary to form various patterns or protrusions on the surface to roughen the surface, thereby increasing the surface area of the inner surface of the case.

Referring to FIG. 5A, the side plate 310 of the can is formed with an intersecting diagonal stripe 360. That is, roughness is given to the surface of the side plate 310. In FIG. 5A, the surface of the side plate 310 is roughened by forming intersecting diagonal stripes 360. However, this is only an example. Thus, various patterns may be formed to roughen the surface of the side plate 310. Can be formed.

In addition, to roughen the surface of the side plate 310, referring to Figure 5b, a plurality of embossed projections 370 are formed. When such stripes or embossed protrusions are formed on the surface of the side plate 310 to roughen the surface of the side plate 310, the surface area of the can having good affinity with the electrolyte is enlarged and the sealing tape 250 is attached to the outer circumferential surface of the electrode assembly. The effect of can be made relatively small. Therefore, the sedimentation rate of electrolyte solution can be improved.

6 is a perspective view of an electrode assembly having a sealing tape 250 attached to an outer circumferential surface thereof, and FIG. 7 is a cross-sectional view illustrating a shape in which the electrode assembly of FIG. 6 is inserted into a can having a side plate having a roughened surface. Referring to FIG. 6, a positive electrode plate and a negative electrode plate facing each other, a separator interposed between the positive electrode plate and the negative electrode plate are wound in a cylindrical shape, and the positive electrode tab 215 and the negative electrode tab 225 protrude to the top and bottom of the electrode assembly. have. On the outer circumferential surface of the electrode assembly 200, an end portion of the separator wound from the center of the electrode assembly 200 to the outside is exposed. In order to prevent the wound electrode assembly 200 from loosening, the sealing ring tape 250 is attached to the outer circumferential surface of the electrode assembly 200 including the end of the separator. Referring to FIG. 7, an electrode assembly to which a sealing tape 250 is attached is inserted into the can. The inside of the side plate 310 of the can is roughly formed, and thus a certain amount of space is formed even when the sealing tape 250 and the inside of the side plate 310 are in close contact with each other. Through this space, the electrolyte is injected and the injected electrolyte is settled to the bottom of the can due to intermolecular cohesion and capillary action.

At this time, in order to further improve the settling speed of the electrolyte solution, a material familiar with the electrolyte may be coated on the surface of the existing sealing tape 250. A familiar material for the electrolyte is PVdF 761. PVdF is a structure in which -CH2-CF2- is repeated and is used as a binder when coating an electrode active material on a current collector. The PVdF 761 has good spreadability when the nonaqueous electrolyte is buried. Therefore, coating the surface of the existing sealing tape 250 with PVdF 761 can improve the impregnation of the electrolyte.

2, the cap assembly 400 includes a safety vent 410, a current blocking means 420, a secondary protective element 480, and a cap up 490. The safety vent 410 has a plate-like protrusion formed at the center to protrude downward, and is positioned below the cap assembly 400, and the protrusion is deformed upward by the pressure generated inside the secondary battery. The positive electrode tab 215 drawn from the positive electrode plate 210 and the negative electrode plate 220 of the electrode assembly 200, for example, the positive electrode plate 210, is welded to a predetermined surface of the lower surface of the safety vent 410. The safety vent 410 and the positive electrode plate 210 of the electrode assembly 200 are electrically connected. Here, the other electrode plate, for example, the cathode, of the positive electrode plate 210 and the negative electrode plate 220 is electrically connected to the can 300 by a tab or direct contact method.

As described above, the present invention is not limited to the specific preferred embodiments described above, and any person having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Various modifications are possible, of course, and such changes are within the scope of the claims.

According to the lithium secondary battery according to the present invention, by forming a recess in the inner surface of the case to improve the settling speed of the electrolyte, or by forming a rough inner surface to increase the surface area having affinity with the electrolyte, By improving the impregnation of the electrolyte solution, it is possible to shorten the electrolyte solution impregnation process time, which takes up a large part of the overall process, thereby improving productivity.

Claims (15)

A lithium secondary battery comprising an electrode assembly, a sealing tape attached to an outer circumferential surface of the electrode assembly, a case accommodating the electrode assembly, and a cap assembly sealing an upper opening of the case. Lithium secondary battery, characterized in that the groove is formed on the inner surface of the case in which the case and the electrode assembly contact. The method of claim 1, The groove is a lithium secondary battery, characterized in that formed linearly along the columnar surface from the upper opening to the lower end of the case. The method of claim 1, The groove is a lithium secondary battery, characterized in that the cross-sectional shape in a direction parallel to the bottom surface of the case is any one of a triangle, a square, a semicircle. The method of claim 1, The groove is a lithium secondary battery, characterized in that the depth is less than 15% of the thickness of the case. The method of claim 1, The groove has a depth of less than 37.5㎛ lithium secondary battery. The method of claim 1, The lithium secondary battery is a lithium secondary battery, characterized in that the cylindrical including a cap assembly having a safety vent. The method of claim 6, The case is a lithium secondary battery, characterized in that withstands a pressure three times or more of the operating pressure of the safety vant. The method of claim 6, The case is a lithium secondary battery, characterized in that withstands the internal pressure of more than 15kg / ㎡. The method of claim 1, Lithium secondary battery, characterized in that the sealing tape is coated with a material friendly to the electrolyte. The method of claim 9, The material familiar to the electrolyte is a lithium secondary battery, characterized in that the polymer material. The method of claim 10, The polymer material is a lithium secondary battery, characterized in that PVdF 761. A lithium secondary battery comprising an electrode assembly, a sealing tape attached to an outer circumferential surface of the electrode assembly, a case accommodating the electrode assembly, and a cap assembly sealing an upper opening of the case. The case is a lithium secondary battery, characterized in that the inner surface is rough (rough). The method of claim 12, Lithium secondary battery, characterized in that the sealing tape is coated with a material friendly to the electrolyte. The method of claim 13, The material familiar to the electrolyte is a lithium secondary battery, characterized in that the polymer material. The method of claim 14, The polymer material is a lithium secondary battery, characterized in that PVdF 761.

Images