KR20130008883A - Electrode assembly of excellent productability and secondary battery comprising the same - Google Patents

Abstract

PURPOSE: An electrode assembly with excellent manufacture fairness and a secondary battery including the same are provided to enhance performance and lifetime property of the batteries. CONSTITUTION: An electrode assembly (200) has a structure of reeling a plurality of unit cells(110-140) with a porous detach film(200). The unit cell is composed of a stack type structure in which one or more positive electrodes and one or more negative electrodes are laminated. One or more punched holes(210-240) are formed at an area of the detach film corresponding to the side of the electrode assembly. The unit cell is composed fullcell structure.

Description

Electrode Assembly with Excellent Manufacturing Process and Secondary Battery Comprising the Same {Electrode Assembly of Excellent Productability and Secondary Battery Comprising the Same}

The present invention relates to an electrode assembly having a superior manufacturing processability and a secondary battery including the same, and more particularly, a folding type electrode assembly having a structure in which a plurality of unit cells are wound with a porous separation film, wherein the unit cells are at least one positive electrode. And one or more cathodes are stacked in a stacked structure in which a separator is interposed therebetween, and at least one portion of the separation film corresponding to the side of the electrode assembly of the separator film facilitates injection of electrolyte and discharge of gas. The present invention relates to an electrode assembly in which a hole is drilled.

Due to the development of technology and demand for mobile devices, the demand for secondary batteries is also rapidly increasing. Among them, lithium secondary batteries, which have high energy density, high operating voltage and excellent storage and life characteristics, It is widely used as an energy source.

Lithium secondary batteries are largely classified into cylindrical batteries, square batteries, pouch-type batteries, and the like according to their appearance, and may be classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, and the like depending on the type of electrolyte.

The electrode assembly of the anode / separator / cathode structure constituting the secondary battery is largely classified into a jelly-roll type (winding type) and a stack type (laminate type) depending on its structure. In the jelly-roll type electrode assembly, an electrode active material or the like is coated on a metal foil used as a current collector, dried and pressed, cut into a band shape having a desired width and length, and a cathode and an anode are diaphragm- . The jelly-roll type electrode assembly is suitable for cylindrical batteries, but has disadvantages such as peeling problems of electrode active materials and low space utilization when applied to rectangular or pouch type batteries. On the other hand, the stacked electrode assembly has a structure in which a plurality of anode and cathode unit cells are sequentially stacked, and has an advantage of easily obtaining a rectangular shape, but when the manufacturing process is complicated and an impact is applied, the electrode is pushed and a short circuit occurs. There is a disadvantage that is caused.

In order to solve this problem, as an electrode assembly of a further structure of the jelly-roll type and the stacked type, a full cell or a positive electrode (cathode) / separator / of a certain unit size of the anode / separator / cathode structure A stack-foldable electrode assembly has been developed in which a bicell having a cathode (anode) / separator / anode (cathode) structure is folded using a continuous separation film having a long length.

However, in general, the stack-foldable electrode assembly is surrounded by a separation film on its outer surface, and the separation film is present in multiple layers on the side of some full cells or bicells, so that wettability of the electrolyte during impregnation of the battery is poor. It has a disadvantage. In particular, since the impregnation of the electrolyte is a kind of bottleneck process that takes a lot of time in the manufacturing process of the battery, if the impregnation of the electrolyte takes a lot of time, the overall production process may be greatly reduced.

In addition, the low wettability of the electrolyte may cause problems such as deterioration of the battery performance and shortening of lifespan. In addition, the process speed may be increased because the time for discharging bubbles between the electrodes in a vacuum state is increased during the gas discharge process.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art and the technical problems required from the past.

An object of the present invention is to provide a secondary battery having a structure that can improve the performance and manufacturing processability of the battery by winding the electrode assembly with a separation film of a specific structure that improves the wettability of the electrode assembly to the electrolyte and easy gas discharge. .

An electrode assembly according to the present invention for achieving the above object, as a folding electrode assembly of a structure in which a plurality of unit cells wound with a porous separation film,

The unit cell has a stack-type structure in which at least one positive electrode and at least one negative electrode are stacked in a state where a separator is interposed therebetween.

The separation film corresponding to the side of the electrode assembly of the separation film is composed of one or more perforated holes are formed to facilitate the injection of the electrolyte and the discharge of the gas.

Therefore, the electrode assembly according to the present invention is stacked in a state in which the unit cells of the stack-type structure of a predetermined unit is sequentially wound by the separation film, the hole formed in the separation film corresponding to the side of the electrode assembly Through the impregnation of the electrolyte can improve the wettability and easily discharge the gas, ultimately improve the performance and life characteristics of the battery and manufacturing processability.

An electrode assembly according to the present invention is a kind of stack / foldable electrode assembly, and details thereof are disclosed in Korean Patent Application Publication Nos. 2001-82058, 2001-82059, 2001-82060, and the like.

Specifically, the unit cell of the stacked structure is not particularly limited as long as it consists of a cathode and an anode, and a separator interposed therebetween, and may be, for example, a bi-cell or a full cell.

The bicell is a cell composed of electrodes having the same polarity, and means a unit cell having a structure in which an anode is located at both sides and a structure in which a cathode is located at both sides. For example, the bicell may include an anode / separator / cathode / separator / anode cell and a cathode / separator / anode / separator / cathode cell. In order to configure the electrode assembly using the bicell, the bicell of the anode / separator / cathode / separator / anode structure and the bicell of the cathode / separator / anode / separator / cathode structure are separated from each other with a separator film interposed therebetween. Multiple bicells must be stacked to face each other.

The full cell is a cell composed of electrodes of opposite polarities, and refers to a unit cell having a structure of an anode, a separator, and a cathode. For example, the full cell may include an anode / separator / cathode cell and an anode / separator / cathode / cathode / anode / separator / cathode cell having the most basic structure. In order to configure the electrode assembly using such a full cell, a plurality of full cells should be stacked such that the positive electrode and the negative electrode face each other with the separation film interposed therebetween.

In one preferred example, the separation film may have a structure in which one or more perforation holes are formed in portions of the separation film corresponding to both sides of the electrode assembly.

In the present invention, both sides of the electrode assembly mean both sides of the outer circumferential surface of the electrode assembly except for the top and bottom surfaces of the electrode assembly, except for the front surface from which the electrode terminals protrude and the rear surface facing the electrode assembly.

In the above structure, it is characterized in that the perforation holes are formed on the separation film at both sides of the position, the part of the separation film is a concept including both the inner side portion as well as the outer side portion of the portion of the separation film. .

In the present invention, the boring hole is not particularly limited as long as it can easily pass through the electrolyte and gas, preferably has a diameter of 10 ㎛ to 5 mm. If the diameter of the punched hole is too large, the separation film is likely to be damaged between the punched punched holes or adjacent punched holes during winding, and if the diameter of the drilled holes is too small, the electrolyte and gas are not easily passed, so that the desired wettability is achieved. And gas emissions cannot be achieved, which is undesirable.

The perforation hole may be formed in various forms, for example, may be in the form of a circle or a polygon. Particularly, in the case of the rectangular structure, since the perforation hole can be formed more closely on the long sheet type separation film, it is very preferable.

The perforation holes may be formed on a plurality of positions corresponding to the separation widths between the unit cells when the unit cells are positioned on the separation film for winding for manufacturing the electrode assembly. As a result, the perforation hole is located on the side of the electrode assembly during the winding process, and the separation width may vary depending on the number of stacked unit cells and the stacked structure. In addition, since the perforation hole is formed in a portion corresponding to the side of each unit cell in the separation film, it is preferable that the perforated hole is formed in a shape corresponding to the side of the unit cell, the unit cell, depending on the size of the perforation hole At intervals of the separation width between the two, it may be formed in the form of one row or multiple rows perpendicular to the longitudinal direction of the separation film.

Accordingly, the electrode assembly of the present invention can be moved in the longitudinal direction as well as in the left and right directions by the perforation hole in comparison with the prior art in which the electrolyte is introduced and the gas is discharged in the longitudinal direction of the electrode assembly. The time to reach can be shortened, which greatly shortens the process time. In addition, as compared with the prior art formed in the portion corresponding to the entire surface of the unit cell, it is very preferable because the occurrence of short can be prevented in advance.

The perforation hole may be formed by various methods, for example, may be formed by cutting the separation film with a punch having a size corresponding to the diameter of the perforation hole, partially separating the separation film into a needle having a diameter of a predetermined size. It may be formed by breaking. Here, when forming the punched holes using the needle body, since the diameter of the punched holes may be somewhat smaller than when using the punch, it is possible to implement a desired wettability and gas discharge by increasing the number of punched holes.

The present invention also provides a secondary battery comprising the electrode assembly, wherein the secondary battery may be preferably applied to a lithium secondary battery prepared by impregnating an electrode assembly with a lithium-containing electrolyte.

As described above, the electrode assembly according to the present invention is excellent in the wettability and gas discharge for the electrolyte, and ultimately has the effect of improving the performance and life characteristics of the battery and greatly improve the manufacturing processability of the battery.

1 is a cross-sectional view of a manufacturing process of an electrode assembly according to one embodiment of the present invention;
FIG. 2 is a plan view of a unit cell and a separation film forming the electrode assembly of FIG. 1; FIG.

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

1 is a cross-sectional view schematically showing a manufacturing process of an electrode assembly according to an embodiment of the present invention, Figure 2 is a plan view of a unit cell and a separation film constituting the electrode assembly of FIG. have.

Referring to these drawings, the folding electrode assembly 100 has a structure in which a plurality of full cells 110, 120, 130, 140... Are wound around the porous separation film 200.

The full cell 140 has a stacked structure in which the anode 10 and the cathode 20 are stacked in a state of being interposed in a separator (not shown), and electrodes at both ends are formed of electrodes having opposite polarities.

The electrode assembly 100 has the full cells 110, 120, 130, 140... In a structure in which the full cells 110, 120, 130, 140 .. are placed on the separation film 200. ) Can be prepared by folding. Therefore, the separation widths of the full cells 110, 120, 130... So that the rectangular perforation holes 210, 220, 230, 240 .. of the separation film 200 may be located at both sides of the electrode assembly 100. Spaced apart.

Specifically, the separation film 200 includes perforation holes 210, 220, 230, 240... Which are spaced apart by a predetermined width in the longitudinal direction thereof. Accordingly, each of the perforation holes 210, 220, 230..., The separation film 200 is arranged in a row in the longitudinal direction of the full cells 110, 120, 130... On the side of the electrode assembly 100. It is formed in.

In this case, the separation distance l ₁ of the first drilling hole 210 in the separation film 200 is equal to the sum of the width (w ₁ ) and the thickness (not shown) of the first full cell 110, The separation distance l ₂ of the first drilling hole 210 and the second drilling hole 220 is equal to the sum of the width w ₁ and the thickness (not shown) of the first full cell 110. Substantially, since the thickness of the first full cell 110 is a very small value, the separation distance l ₁ , l ₂ between the first drilling hole 210 and the first drilling hole 210 and the second drilling hole 220. Is equal to the width w ₁ of the first full cell 110. However, as the number of full cells to be stacked increases, the thickness of the full cells also increases, so that the separation distance should be calculated in consideration of the thickness values of the full cells.

Thus, the electrolyte and gas may move not only in the length (A) direction but also in the left and right directions (B) by the perforation holes 210, 220, and 230 .. of the separation film 200, thereby greatly reducing the process time. Can be.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (11)

A folding electrode assembly having a structure in which a plurality of unit cells are wound with a porous separation film,
The unit cell has a stack-type structure in which at least one positive electrode and at least one negative electrode are stacked in a state where a separator is interposed therebetween.
Electrode assembly, characterized in that the separation film corresponding to the side of the electrode assembly of the separation film is formed with one or more perforation holes to facilitate the injection of the electrolyte and the discharge of the gas. The electrode assembly of claim 1, wherein the unit cell has a bicell structure in which electrodes at both ends are electrodes having the same polarity. The electrode assembly of claim 1, wherein the unit cell has a full cell structure in which electrodes at both ends are electrodes having opposite polarities. The electrode assembly of claim 1, wherein each of the separation films has one or more perforation holes formed in portions of the separation film corresponding to both sides of the electrode assembly. The electrode assembly of claim 1, wherein the drilling hole has a diameter of 10 µm to 5 mm. The electrode assembly of claim 1, wherein the drilling hole has a circular or polygonal shape. The method of claim 1, wherein the perforation hole, when positioning the unit cells on the separation film in the winding process for manufacturing the electrode assembly, characterized in that formed on a position corresponding to the separation width between the unit cells. Electrode assembly. The electrode assembly of claim 1, wherein the drilling hole is formed by cutting the separation film with a punch having a size corresponding to the shape thereof. The electrode assembly of claim 1, wherein the hole is formed by partially breaking the separation film into a needle having a diameter of a predetermined size. A secondary battery comprising the electrode assembly according to any one of claims 1 to 9. The secondary battery of claim 10, wherein the secondary battery is prepared by impregnating an electrode assembly with a lithium-containing electrolyte.

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