KR20060103613A - Pouch type secondary battery and preparation thereof - Google Patents

Abstract

The present invention relates to a pouch type secondary battery and a method of manufacturing the same, characterized in that two electrode tabs (attach) is attached to each of the positive electrode and the negative electrode, the secondary battery according to the present invention is superior safety compared to the conventional secondary battery And high rate characteristics.

Description

Pouch type secondary battery and manufacturing method thereof {POUCH TYPE SECONDARY BATTERY AND PREPARATION THEREOF}

1 is a cross-sectional view showing the electrode structure of a lithium secondary battery according to the present invention,

Figure 2 is a side view showing a jelly-roll (jelly-roll) of the battery according to the present invention,

Figure 3 is a high rate characteristic comparison graph of the lithium secondary battery prepared in Examples and Comparative Examples,

Figure 4 is a graph of the comparison of the surface temperature of the battery during the large current discharge of the lithium secondary battery prepared in Examples and Comparative Examples.

* Brief description of the reference numbers

(a): electrode tab (b): lead wire

The present invention relates to a pouch type secondary battery having excellent high rate characteristics and stability, and a manufacturing method thereof.

In general, a secondary battery refers to a battery capable of charging and discharging, unlike a primary battery that is not rechargeable, and is widely used in the field of advanced electronic devices. In particular, lithium secondary batteries that commonly use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials are nickel-cadmium batteries and nickel- batteries that are frequently used as power sources for electronic equipment such as remote control and power tools. Attempts have been made to replace nickel-cadmium batteries or nickel-hydrogen batteries because the operating voltage is more than three times higher and the energy density per unit weight is higher than that of hydrogen batteries. However, the current lithium battery is low in high rate characteristics compared to other batteries, and the situation is somewhat insufficient in terms of safety, and studies to improve it are being conducted.

In particular, the pouch-type lithium secondary battery stores a jelly-roll obtained by stacking or winding in a form in which a separator is inserted between a positive electrode and a negative electrode in a molded aluminum (Al) -laminate film. As manufactured, it has the advantage of being light in weight

Among the pouch-type lithium batteries, the stacking type battery is advantageous compared to the winding type battery in terms of high yield characteristics, but the manufacturing process of the battery is very complicated and the yield is low. On the other hand, in the case of a conventional wound battery provided with one electrode tab for each electrode, the manufacturing process is very simple, but when the capacity of the battery is increased, especially when the battery capacity is about 2000 mAh or more, a large current discharge When the high rate characteristic is rapidly reduced and the surface temperature of the battery is high, there is a problem of low safety.

Accordingly, an object of the present invention is to provide a pouch type secondary battery excellent in safety and high rate characteristics and a method of manufacturing the battery.

In order to achieve the above object, in the present invention, in the pouch type secondary battery comprising a jelly-roll (jelly-roll) comprising a cathode, an anode and a separator and an electrolyte disposed between these electrodes, each of the two electrodes is 2 Provided is a pouch type secondary battery having two electrode tabs and having a structure in which a lead wire is coupled to each of the electrode tabs in which tabs on the same electrode are bonded to each other.

In the present invention, 1) attaching each one of the electrode tabs to the both ends of the positive electrode and the negative electrode, respectively, 2) inserting a separator between the positive electrode and the negative electrode attached to the electrode tab and then wound by winding the jelly-roll Pouch type comprising the steps of: obtaining a battery cell of the form; 3) attaching each electrode lead wire after welding the same electrode tabs to each other, and 4) inserting the battery cell with a lead wire into a pouch and injecting an electrolyte solution It provides a method for producing a secondary battery.

Hereinafter, the present invention will be described in more detail.

The secondary battery according to the present invention is characterized in that a total of four electrode tabs, each of which is provided in each of the positive electrode and the negative electrode.

In the present invention, the anode consists of an anode coating portion coated with a positive electrode active material and an uncoated portion at both ends not coated with the cathode active material, and a cathode is made of a cathode coating portion and a cathode coated with a cathode active material. The active material is coated with both ends of the uncoated end, where the electrode uncoated means a region where the electrode active material is not coated on both ends of each electrode.

In addition, the electrode tabs that cause the flow of current while connecting the inside and the outside of the battery are fixedly attached to both end portions of the positive and negative ends by, for example, welding or the like, as shown in FIG. Here, each electrode tab is formed in the electrode non-coating portion, rather than the electrode coating portion coated with the electrode active material, there is no capacity loss of the electrode.

In the present invention, the size of the tab depends on the battery capacity, for example, if the battery capacity is about 2000 mAh or more, it may be about 10 mm (butterfly) x 0.1 mm (thickness), but there is no particular limitation.

A battery obtained by inserting a porous separator between the two tabbed positive and negative electrodes, wound into a roll, and called a jelly-roll as shown in FIG. 2. A cell is formed, wherein electrode tabs protrude outward from the top of the battery cell. The electrode tabs drawn out of the jelly-roll are joined together by welding two tabs formed on the same electrode, and then a lead wire of each electrode is connected by welding.

The positive electrode and the negative electrode according to the present invention may use a conventional one used in a secondary battery. For example, in the case of a lithium ion battery, a positive electrode active material may be a mixture containing a binder, a plasticizer, a conductive material, and the like in a lithium-based oxide. As a negative electrode active material, a mixture containing a binder, a plasticizer, a conductive material, and the like in a carbon material may be used.

In addition, the electrolyte solution used in the present invention is not particularly limited, and both liquid electrolytes and polymer electrolytes used in the art may be used, and the separator used in the present invention is typically used in the case of lithium ion batteries such as polyethylene or polypropylene. A porous plate made of a polymeric material, which insulates the anode and cathode from each other, while allowing active material ions to be exchanged between the electrodes.

The pouch-type secondary battery according to the present invention can be manufactured by inserting the battery cell with the lead wires into the pouch as described above and injecting the electrolyte solution.

As described above, the secondary battery according to the present invention has two electrode tabs attached to each electrode, so that the amount of current applied by one tab is reduced by half compared to a conventional battery having one electrode tab attached to each electrode. As a result, the so-called IR (V = IR) drop due to the resistance of the path through which the current flows in the electrode is greatly reduced, thereby increasing the high rate characteristic, and also generating heat generated by the IR drop at the electrode tab during a large current discharge. Safety is also improved.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

<Example>

A negative electrode active material composition was prepared by mixing 93.76 g of graphite, 6.24 g of polyvinylidene fluoride, and 57.5 g of N-methylpyrrolidone. The obtained negative electrode active material slurry was coated using a die coater leaving both ends 17 mm on both surfaces of the copper foil, and dried and pressed to prepare a negative electrode. Subsequently, negative electrode tabs having a width of 10 mm and a thickness of 0.1 mm were welded and attached to both ends of the non-coated ends where the negative electrode active material was not coated.

A positive electrode active material composition was prepared by mixing 88 g of LiCoO ₂ , 6.8 g of carbon black, 5.2 g of polyvinylidene fluoride, and 52.5 g of N-methylpyrrolidone. The obtained positive electrode active material slurry was coated using a die coater leaving both ends 20 mm on both surfaces of the aluminum foil, dried and pressed to prepare a positive electrode. Subsequently, positive electrode tabs having a width of 10 mm and a thickness of 0.1 mm were welded to the plain portions at both ends not coated with the positive electrode active material, respectively.

A cathode roll and a cathode with electrode tabs attached to both ends of the plain and a separator (20 μm, Cellgard 2320 microporous film) were wound to make a jelly roll, and then the same electrode tabs were welded together. After the bonding, the lead wires of the electrodes were welded and attached to each of the molded Al laminate films, and partially sealed.

Subsequently, 2 g of poly (2-vinylpyridine-co-styrene) (PVPS, Aldrich) and 0.5 g of 1,4-butanediol diglycidyl ether (BDDGE, Aldrich) were added to an electrolyte solution (LiPF ₆ 12.1 weight). %, Ethylene carbonate (EC) / propylene carbonate (PC) / dimethyl carbonate (DMC) = 21 / 35.7 / 31.2% by weight), and then injected into a jelly-containing Al-laminate film and then completely sealed. Then, the polymer was cured at 65 ° C. for 24 hours to prepare a lithium secondary battery according to the present invention.

Comparative Example

A lithium secondary battery was manufactured in the same manner as in Example, except that the electrode tab was attached to only one of the plain portions at both ends of the positive electrode and the negative electrode to form one electrode tab for each electrode.

<Test Example>

The high rate characteristics of the lithium batteries prepared in Examples and Comparative Examples were measured using a maco test equipment, and the results are shown in FIG. 3 as a graph. From the graph of FIG. 3, the lithium battery of the present invention with two tabs attached to each electrode (Example) shows much higher high rate characteristics than the battery with one tab attached per electrode (Comparative Example) (7C 42% higher during discharge).

Furthermore, the surface temperature of the battery was measured when a large current of 28.7A was supplied to the lithium secondary batteries prepared in Examples and Comparative Examples, and the results are shown in FIG. 4. From FIG. 4, it can be seen that a battery including two electrode tabs per electrode manufactured in the example has a low battery surface temperature during high current discharge compared to the battery manufactured in the comparative example, thereby increasing safety.

As described above, in the secondary battery according to the present invention, two electrode tabs are attached to each electrode, thereby exhibiting excellent safety and high rate characteristics.

Claims (3)

In a pouch type secondary battery comprising a cathode, an anode, and a jelly-roll including an separator and an electrolyte disposed between these electrodes, each of the two electrodes has two electrode tabs and the same electrode. A pouch type secondary battery having a structure in which a lead wire is coupled to each of the electrode tabs bonded to each other by tabs on the tabs. The method of claim 1, A pouch type secondary battery, characterized in that one electrode tab is attached to each of the both ends of the positive electrode and the negative electrode. 1) attaching one electrode tab to each of the plain ends of the positive electrode and the negative electrode, 2) inserting a separator between the positive electrode and the negative electrode to which the two tabs are attached, and then wound and wound to form a jelly-roll battery cell The method of claim 1, comprising the steps of: 3) welding the same electrode tabs to each other, and then attaching the electrode lead wires, and 4) inserting the battery cell with the lead wires into the pouch and injecting the electrolyte solution. Method for producing a battery.

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