KR100624959B1 - Lithium Secondary Battery and Manufacturing Method Thereof - Google Patents

Abstract

The present invention relates to a lithium secondary battery having a structure in which an electrode assembly wound in a substantially cylindrical shape is housed in a pouch packaging material, and a method of manufacturing the lithium secondary battery of the present invention. An electrode assembly having a separator interposed between the electrode plate and the second electrode plate and wound in a cylindrical shape; It characterized in that it comprises a pouch packaging material having a space for accommodating the electrode assembly wound in the cylindrical shape.

Lithium Secondary Battery, Cylindrical, Pouch Case

Description

Lithium secondary battery and method of manufacturing the same {Li Secondary Battery and Method of fabricating the same}

1A is an exploded perspective view of a rechargeable lithium battery according to one embodiment of the present invention.

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

1C is a cross sectional view along line A-A in FIG. 1B;

On the other hand, Figure 2 is a flow chart illustrating a method of manufacturing a lithium secondary battery according to an embodiment of the present invention.

3A to 3D are views for explaining a method of manufacturing a lithium secondary battery according to one embodiment of the present invention.

(Explanation of symbols for main parts of drawing)

100; Lithium secondary battery 200; Electrode assembly

210; First electrode plate 215; Second electrode plate

220; Second electrode plate 225; Second electrode plate

230; Separator 240; Insulation tape

300; Pouch sheath 310; First side

315; First spaces 317 and 327; flange

320; Second side 325; 2nd space

330; Tangential line 340; Gas capture space

350; A first moving path 360; 2nd driveway

400; Electrolyte

The present invention relates to a lithium secondary battery and a method of manufacturing the same, and more particularly, to a lithium secondary battery and a method for manufacturing the same, a structure in which an electrode assembly wound in a substantially cylindrical shape is housed in a pouch case.

Recently, compact and lightweight electric / electronic devices such as cellular phones, notebook computers, camcorders, etc. have been actively developed and produced. These portable electric / electronic devices have a battery pack that can be operated in a place where no separate power source is provided. The built-in battery pack includes at least one battery therein for outputting a predetermined level of voltage for driving the portable electric / electronic device for a period of time.

In view of economical aspects, the battery pack employs a secondary battery capable of charging and discharging. Representative secondary batteries include lithium secondary batteries such as nickel-cadmium (Ni-Cd) batteries, nickel-hydrogen (Ni-MH) batteries, lithium (Li) batteries, and lithium ion (Li-ion) batteries.

In particular, the lithium secondary battery has an operating voltage of 3.6 V, which is three times higher than that of a nickel-cadmium battery or a nickel-hydrogen battery, which is widely used as a power source for portable electronic equipment, and rapidly expands in terms of high energy density per unit weight. There is a trend.

Such lithium secondary batteries mainly use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials. In general, a battery is classified into a liquid electrolyte battery and a polymer electrolyte battery according to the type of electrolyte, and a battery using a liquid electrolyte is called a lithium ion battery, and a battery using a polymer electrolyte is called a lithium polymer battery. Moreover, although a lithium secondary battery is manufactured in various shapes, typical shapes include cylindrical shape, square shape, and pouch type.

Typically, the cylindrical lithium secondary battery has a positive electrode plate coated with a positive electrode active material capable of generating lithium ions (Li-ion), a negative electrode plate coated with a graphite negative electrode active material, and the positive electrode plate and the negative electrode plate An electrode assembly in which a separator is disposed between the electrode assembly to prevent shorting and allow only movement of lithium ions, a cylindrical case to which the electrode assembly is coupled, and a cap assembly to block the case to suppress detachment of the electrode assembly. And an electrolyte solution injected into the case to enable movement of lithium ions.

The manufacturing method of such a cylindrical lithium ion secondary battery is as follows.

First, the negative electrode plate on which the predetermined active material layer is formed, the separator and the positive electrode plate on which the predetermined active material layer is formed are laminated together, and then one end is bonded to a rod-shaped winding shaft, and then wound in a substantially cylindrical form to form an electrode assembly.

Subsequently, after inserting the electrode assembly into the cylindrical case, the electrolyte is injected, and then the cap assembly is welded to the upper portion of the cylindrical case, thereby completing a substantially cylindrical lithium ion secondary battery.

In the cylindrical lithium secondary battery, when charging, lithium ions penetrate between the lattice of graphite which is a negative electrode active material, thereby causing expansion due to charging. However, the cylindrical lithium secondary battery is made of a high-strength material, the cylindrical case of any one of aluminum (Al), iron (Fe) and their alloys to suppress expansion due to the charging. Accordingly, the charging efficiency of the lithium secondary battery is reduced, and thus there is a problem against the recent trend of maximizing the capacity of the lithium secondary battery.

In addition, the cylindrical lithium secondary battery is provided with a safety device such as a safety interrupt device (CID) and a breaking pressure of about 9 kgf / cm 2 in general, in the cap assembly to improve safety. There is a problem that the manufacturing cost of the lithium secondary battery increases.

In addition, since the cylindrical lithium secondary battery has a structure in which the cap assembly is coupled to the upper portion of the cylindrical case, there is a problem in that the battery capacity is lowered compared to the volume of the cylindrical case.

An object of the present invention is to solve the above-mentioned problems of the prior art, the present invention is to provide a lithium secondary battery and a method for manufacturing the lithium secondary battery consisting of a structure in which an electrode assembly wound in a substantially cylindrical shape is housed in a pouch case. There is this.

The lithium secondary battery of the present invention for achieving the above object has a separator interposed between the first electrode plate, the second electrode plate, the first electrode plate and the second electrode plate, the electrode wound in a cylindrical shape An assembly; It characterized in that it comprises a pouch packaging material having a space for accommodating the electrode assembly wound in the cylindrical shape.

The pouch sheathing material is divided into a first surface and a second surface on the basis of a fold line, and a space for accommodating the electrode assembly includes a first space formed on the first surface and a second surface formed on the second surface. It is preferable that the space is formed, and the first space and the second space preferably have a shape in which the shape of the space is cut in the axial direction of a substantially cylindrical shape.

The pouch packaging material includes a core and a heat fusion layer formed on an upper surface of the core; It is preferable that the core is made of an insulating film formed on the lower surface, more preferably, the core is made of aluminum (Al), the heat-sealing layer is made of modified polypropylene, the insulating film is nylon or polyethylene terephthalate It is preferable to consist of either.

The pouch packaging material preferably has a breaking pressure of 9 kgf / cm 2 or less.

In addition, the method of manufacturing a lithium secondary battery of the present invention comprises the steps of preparing a pouch case having a space for accommodating the electrode assembly and the gas collecting space; Receiving an electrode assembly in the pouch case; Heat-sealing the pouch sheathing material while maintaining a first moving path located around a space for accommodating the electrode assembly and a second moving path located in an area between the gas collecting space and a space for accommodating the electrode assembly; Steps; Injecting electrolyte through the first moving path and impregnating the electrode assembly; Collecting gas into the gas collecting space by initial charging and discharging; And cutting the space between the space for accommodating the electrode assembly and the gas collection space to remove the gas collection space.

The first moving path is preferably located at a portion of the flange around the gas collection space that is opposite the space for receiving the electrode assembly.

After injecting the electrolyte and impregnating the electrode assembly, the method may further include sealing the first moving path.

The method may further include sealing the second moving path after collecting the gas into the gas collecting space by the initial charging and discharging.

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

Like reference numerals in the drawings denote like elements.

1A is an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention, FIG. 1B is a perspective view of a lithium secondary battery after coupling according to an embodiment of the present invention, and FIG. 1C is a cross-sectional view taken along line AA of FIG. 1B. to be.

As illustrated in FIGS. 1A to 1C, the cylindrical lithium secondary battery 100 according to the exemplary embodiment of the present invention includes an electrode assembly 200 that generates a voltage difference when charging and discharging, and accommodates the electrode assembly 200. The pouch sheath 300 and the pouch sheath 300 are injected into the pouch sheath 300 and have an electrolytic solution 400 that allows lithium ions to move between the electrode assemblies 200.

The electrode assembly 200 may include any one of a positive electrode active material and a negative electrode active material, for example, a first electrode plate 210 coated with a positive electrode active material, another one of the positive electrode active material and the negative electrode active material, for example, a negative electrode active material. A short of the first electrode plate 210 and the second electrode plate 220 is disposed between the coated second electrode plate 220, the first electrode plate 210, and the second electrode plate 220. ) And a separator 230 that allows only lithium ions to move. In addition, the first electrode plate 210, the second electrode plate 220, and the separator 230 are wound in a substantially cylindrical shape and accommodated in the case 300.

In addition, the first electrode plate 210 is generally made of aluminum (Al) and is bonded to the first electrode tab 215 protruding a predetermined length. The second electrode plate 220 is generally made of nickel (Ni) and has a second electrode tab 225 protruding to a predetermined length. However, in the present invention, the first electrode tab 215 and the second electrode tab 215 are bonded to each other. The material of the electrode tab 225 is not limited. In addition, although the first electrode tab 215 and the second electrode tab 225 only show structures that protrude in opposite directions on the drawing, the present invention does not limit the protruding direction or the first electrode tab. The 215 and the second electrode tab 225 may protrude in the same direction.

In addition, a short circuit between the first electrode plate 210 and the second electrode plate 220 is prevented at the boundary portion from which the first electrode tab 215 and the second electrode tab 225 are drawn out from the electrode assembly 200. Alternatively, the first electrode tab 215 and the second electrode tab 225 may be insulated with insulating tape 240 to prevent the pouch sheath 300 from being short-circuited.

The pouch sheath 300 is formed of a metal material such as aluminum (Al), a core portion 300a, a heat seal layer 300b formed on an upper surface of the core portion 300a, and the core portion 300a. It is made of an insulating film 300c formed on the lower surface. The heat seal layer 300b serves as an adhesive layer using a modified polypropylene, for example, CPP (Casted Polypropylene), which is a polymer resin, and the insulating film 300c may be formed of a resin material such as nylon or polyethylene terephthalate (PET). It may be, but is not limited to the structure and material of the pouch packaging material 300.

In addition, the pouch packaging material 300 is divided into a first surface 310 and a second surface 320 through a fold line 330. A first space 315 is formed on the first surface 310 of the pouch sheath 300 to accommodate the electrode assembly 200 wound in a substantially cylindrical shape. In addition, a second space 325 corresponding to the first space 315 of the first surface 310 is formed on the second surface 320 of the pouch packaging material 300. In this case, since the first space 315 and the second space 325 are spaces for accommodating the substantially cylindrical electrode assembly 200, the space of the first space 315 and the second space 325 is cut out in a substantially cylindrical axial direction. It is preferable to make. That is, the space for accommodating the electrode assembly 200 includes a first space 315 of the first surface 310 and a second space 325 of the second surface 320.

In addition, the portions of the edges of the first space 315 and the second space 325 of the first surface 310 and the second surface 320 are flanges 317 and 327 which are joined when the pouch sheath 300 is sealed. Acts as)

In addition, the breaking pressure of the pouch packaging material 300 is preferably 9kgf / ㎠ or less. In general, the breaking pressure of the pouch sheath 300 is about 3 kgf / cm 2.

The electrolyte 400 serves as a moving medium of lithium ions (Li Ion) generated by an electrochemical reaction at the positive and negative electrodes inside the battery during charging and discharging, which is a non-aqueous water mixture of lithium salts and high purity organic solvents. The organic electrolyte may be. In addition, the electrolyte 400 may be a polymer using a polymer electrolyte, and the type of the electrolyte material is not limited thereto.

Although not shown in the drawings, a protection circuit module for controlling charging, discharging, and malfunction of the lithium secondary battery 100 may be further provided. The protection circuit module is electrically connected to the first electrode tab 215 and the second electrode tab 225 of the electrode assembly 200.

2 is a flowchart illustrating a method of manufacturing a rechargeable lithium battery according to one embodiment of the present invention.

Referring to FIG. 2, the manufacturing process of the pouch type secondary battery according to the preferred embodiment of the present invention may include preparing a pouch case having a first space and a second space and a gas collecting space for accommodating an electrode assembly ( S1), accommodating the substantially cylindrical electrode assembly in the pouch sheathing material (S2), and heat-sealing the pouch sheathing material except the first movement path and the second movement path (S3), through the first movement path. Injecting and impregnating an electrolyte solution (S4), heat-sealing the first moving path (S5), performing initial charging and discharging, collecting gas into the gas collecting space (S6), and the second movement. After the heat-sealing of the furnace, the process includes the step of cutting and removing the gas collection space (S7), thereby manufacturing a lithium secondary battery according to an embodiment of the present invention.

3A to 3D are views for explaining a method of manufacturing a lithium secondary battery according to one embodiment of the present invention.

Referring to FIG. 3A, spaces 315 and 325 for accommodating an electrode assembly 200 wound in a substantially cylindrical shape, and gases generated during initial charging and discharging after impregnation of the electrolyte solution 400 of the electrode assembly 200 are described. To prepare a pouch packaging 300 having a gas collecting space 340 for collecting the.

In this case, a space for accommodating the electrode assembly 200 includes the first space 315 and the second space 325.

In addition, the pouch sheath 300 is divided into a first surface 310 and a second surface 320 based on the fold line 330, and among the first surface 310 and the second surface 320. Any one, for example, the first surface 310, any one of the first space 315 and the second space 325, for example, the first space 315 and the gas collection space 340 Is formed. In addition, the other of the first surface 310 and the second surface 320, for example, the second surface 320, the other of the first space 315 and the second space 325, For example, the second space 325 is formed.

Referring to FIG. 3B, after preparing a pouch case 300 having a first space 315, a second space 325, and a gas collection space 340, which are spaces for accommodating the electrode assembly 200, Prepare the electrode assembly 200.

In this case, as shown in FIGS. 1A to 1C, the electrode assembly 200 is disposed between the first electrode plate 210, the second electrode plate 220, the positive electrode plate 210, and the negative electrode plate 220. The separator 230 interposed therebetween is wound and formed in a substantially cylindrical shape.

On the other hand, the order of preparing the electrode assembly 200 and the pouch packaging material 300 is not necessarily limited thereto, and the pouch packaging material 300 may be prepared after preparing the electrode assembly 200 first.

After preparing the electrode assembly 200, the electrode assembly 200 may have a substantially cylindrical shape in one of the first space 315 and the second space 325, for example, the first space 315. The wound electrode assembly 200 is received.

After receiving the electrode assembly 200 in the first space 315, the pouch sheath 300 is folded along the fold line 330, the first surface 310 and the second surface 320 ) Abut.

Then, an edge portion of the first space 315 and the second space 325 and the gas collection space 12b where the first surface 310 and the second surface 320 of the pouch packaging material 300 abut, That is, the flanges 317 and 327 are thermally bonded to each other.

The thermal fusion is a process of applying heat and pressure to the flanges 317 and 327 and bonding the heat-sealed layer 300b to each other. The first and second spaces 315 and 2, for accommodating the electrode assembly 200, A portion of the flanges 317 and 327 (hereinafter referred to as a "first movement path") excluding the region between the 325 and the gas collection space 340, and a first to receive the electrode assembly 200 A portion 360 of the flange 317, 327 between the space 315 and the second space 325 and the gas collection space 340 (hereinafter referred to as the “second travel path”) intentionally excludes heat fusion. do. Preferably, the first movement path 15 is preferably located on the flanges 317 and 327 opposite to the first space 315 and the second space 325. That is, the first movement path 350 is formed at a portion of the flanges 317 and 327 opposite to the space for accommodating the electrode assembly 200 among the flanges 317 and 327 around the gas collection space 340. The second movement path 360 is formed in a portion of the flanges 317 and 327 between the space for accommodating the electrode assembly 200 and the gas collection space 340.

In other words, the heat fusion is to heat-seaze the pouch case 300 while maintaining the first movement path 350 and the second movement path 360.

After performing the heat fusion process, the gas collecting space 340 as an upper portion, the electrolyte 400 is injected through the first movement path 350, and exposed to a vacuum atmosphere to expose the electrolyte 400 The electrode assembly 200 is impregnated.

Referring to FIG. 2C, after the electrolyte solution 400 is injected and impregnated, the first movement path 350 is thermally fused and bonded.

Thereafter, initial charging and discharging are performed with the gas collecting space 340 as an upper portion. In this case, gas is generated in the electrode assembly 200 during the initial charging and discharging process, and the gas is collected into the gas collecting space 340 through the second moving path 360.

Referring to FIG. 2D, the gas is collected in the gas collecting space 340 through the initial charging and discharging process, and then, between the first space 315 and the second space 325 and the gas collecting space 340. The second moving path 360 is thermally bonded to each other.

Thereafter, the first and second spaces 315 and 325 and the gas collection space 340 are cut to remove the gas collection space 340 in which the gas generated during the initial charging and discharging process is collected. .

Thereafter, although not shown in the drawings, a lithium secondary battery 100 is manufactured by performing a general lithium secondary battery manufacturing process.

The lithium secondary battery 100 as described above has a structure in which the electrode assembly 200 wound in a substantially cylindrical shape is accommodated using the pouch exterior material 300. The lithium secondary battery 100 of the present invention is free to expand the electrode assembly 200 during charging through the flexibility (flexibility) of the pouch packaging material 300, the charging efficiency of the lithium secondary battery 100 is improved Can be.

In addition, since the pouch packaging material 300 generally breaks at a pressure lower than that of a conventional safety band of about 9 kgf / cm 2, the safety of the lithium secondary battery 100 is improved.

In addition, the lithium secondary battery 100 of the present invention may not use a safety device such as a CID and a safety band by using the pouch exterior material 300, and thus, the manufacturing cost of the lithium secondary battery may be lowered.

In addition, the lithium secondary battery 100 does not use a cap assembly including a safety device such as a CID and a safety band, and thus, by using most of the volume of the pouch exterior material as an internal space, battery capacity relative to the total volume may be improved. Can be.

As described above, according to the present invention, the present invention can provide a lithium secondary battery and a method of manufacturing the same, having a structure in which an electrode assembly wound in a substantially cylindrical shape is housed in a pouch case.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (13)

An electrode assembly having a first electrode plate, a second electrode plate, a separator interposed between the first electrode plate and the second electrode plate, and wound in a cylindrical shape; A pouch sheath having a cylindrical inner space for receiving the cylindrical electrode assembly; The pouch sheathing material has a first surface having a first space, which is a space of one semi-cylindrical body divided into two by axially cutting a cylindrical body around a predetermined fold line, and a second space, which is a space of the other semi-cylindrical body. Lithium secondary battery comprising a second surface having a. The method of claim 1, The first electrode plate and the second electrode plate are attached to the first electrode tab and the second electrode tab, And the first electrode tab and the second electrode tab protrude in opposite directions to each other. The method of claim 1, The first electrode plate and the second electrode plate are attached to the first electrode tab and the second electrode tab, And the first electrode tab and the second electrode tab protrude in the same direction. delete delete The method of claim 1, The pouch exterior material Deep, A heat seal layer formed on an upper surface of the core portion; A lithium secondary battery comprising an insulating film formed on the lower surface of the core portion. The method of claim 6, The core is made of aluminum (Al), The heat seal layer is made of a modified polypropylene, The insulating film is a lithium secondary battery, characterized in that made of any one of nylon or polyethylene terephthalate. The method of claim 1, The pouch packaging material is a lithium secondary battery, characterized in that the breaking pressure is 9kgf / ㎠ or less. Preparing a pouch case having an inner space of a cylindrical body having a space for accommodating the electrode assembly and a gas collecting space; Receiving the electrode assembly wound in a cylindrical shape in the pouch case; Heat-sealing the pouch sheathing material while maintaining a first moving path located around a space for accommodating the electrode assembly and a second moving path located in an area between the gas collecting space and a space for accommodating the electrode assembly; Steps; Injecting electrolyte through the first moving path and impregnating the electrode assembly; Collecting gas into the gas collecting space by initial charging and discharging; And removing the gas collection space by cutting between the space for accommodating the electrode assembly and the gas collection space. The method of claim 9, The pouch exterior material is divided into a first surface and a second surface on the basis of a fold line, The space for accommodating the electrode assembly comprises a first space formed on the first surface and a second space formed on the second surface. The method of claim 9, And the first moving path is located at a portion of a flange opposite the space for accommodating the electrode assembly among the flanges surrounding the gas collecting space. The method of claim 9, After injecting the electrolyte and impregnating the electrode assembly, The method of manufacturing a lithium secondary battery further comprises the step of sealing the first moving path. The method of claim 9, After the initial charge and discharge to collect the gas in the gas collecting space, The method of manufacturing a lithium secondary battery further comprises the step of sealing the second moving path.

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