WO2006135183A1

WO2006135183A1 - Lithium secondary battery having anode lead and cathode lead oppositely projected from pouch

Info

Publication number: WO2006135183A1
Application number: PCT/KR2006/002246
Authority: WO
Inventors: Whanjin Roh; Seongwoo Park; Byung Su Jung
Original assignee: Enerland Co., Ltd.
Priority date: 2005-06-13
Filing date: 2006-06-13
Publication date: 2006-12-21
Also published as: KR200394701Y1

Abstract

There is provided a lithium secondary battery having an anode lead and a cathode lead oppositely projected from a pouch. The lithium secondary battery comprises a) a rechargeable electrode assembly comprising a plurality of anode plates and a plurality of cathode plates in which each of the anode plates has one anode tap and each of the cathode plates has one cathode tap, and each of the anode plates and each of the cathode plates are alternatively arranged to each other and separated by a separator; b) a pouch equipped with a cavity into which the rechargeable electrode assembly is accommodated; and c) a anode lead and a cathode lead that deliver current generated from the rechargeable electrode assembly to an outer circuit, wherein the anode lead and the cathode lead are oppositely projected from the pouch based on the electrode assembly and parallel with the anode tap and the cathode tap. The lithium secondary battery provides various advantages such as simple tap treatment and balanced heat distribution. In addition, the width of the battery is not substantially restricted by the presence of the lead.

Description

LITHIUM SECONDARY BATTERY HAVING ANODE LEAD AND CATHODE LEAD OPPOSITELY PROJECTED FROM

POUCH

Technical Field

[1] The present invention relates to a lithium secondary battery, more specifically, to a lithium secondary battery having an anode lead and a cathode lead oppositely projected from a pouch. The present invention relates to a method for fabricating the lithium secondary battery. Background Art

[2] A battery is a device to convert chemical energy of chemicals into electrical energy through electrochemical reaction, and is classified into two categories: a primary battery and a secondary battery. Among the rechargeable secondary battery, a lithium secondary battery is the most important one, because it has the highest voltage and the largest energy density among existing batteries. Currently, the lithium secondary battery is used in a field of electronic appliances such as mobile phones and notebooks.

[3] One of the conventional methods for fabricating the lithium secondary battery is described in Fig. 5. The lithium secondary battery according to the method is fabricated by successively depositing a grid-type anode current collector 111, a matrix- film type anode 112, a matrix-film type separator 113, a matrix-film type cathode 114 and a grid-type cathode current collector 115, followed by laminating the members to integrate them, and folding the laminated members in a zig-zag fashion. The lithium secondary battery prepared from the method comprises the electrode in a form of a continuous, integrated sheet, such that it can be called as a continuous type lithium secondary battery. The continuous type lithium secondary battery has an advantage that it does not require tap treatment due to the use of continuous sheet- like electrode. But it suffers from the damage to the electrodes in the folding process because an electrode active material is detached at the folded position.

[4] In order to avoid the above disadvantages, KR 309,604, 336,396 and 2002-93781 disclose examples in which a plurality of anode plates and a plurality of cathode plates are used. Herein, each of the anode plates and each of the cathode plates are alternatively stacked such that the lithium secondary battery obtained from the method can be called as a stacked lithium secondary battery. The stacked lithium secondary battery does not involve the damage to the electrode plate in the folding process. Fig. 6 is a perspective view showing the conventional stacked lithium secondary battery. With regard to the arrangement of the electrodes on a separator to prepare the stacked lithium secondary battery shown in Fig. 6, please refer to the detailed description of KR 309,604, 336,396 and 2002-93781. As shown in Fig. 6, the conventional lithium secondary battery 1' comprises an anode lead 30a' and a cathode lead 30b' that are projected from a pouch 20 in the same direction. In the Fig. 6, unexplained reference numeral 22' is a cavity for housing an electrode assembly. Investigation on heat distribution on the electrode plate at the charge and discharge of the lithium secondary battery revealed that the heat distribution on the electrode plate is dependent upon the distance from the lead. Specifically, it was observed that as the distance from the lead is farther, the heat is lower. To the contrary, as the distance from the lead is shorter, the heat is higher. In this case, the anode lead 30a' and the cathode lead 30b' projected at the same side reinforces the uneven heat distribution. In other words, when the anode lead 30a' and the cathode lead 30b' are formed at the same side of the pouch 20', uneven heat distribution is even reinforced and the position at the near to the lead (or electrode tap) undergoes much heat. Further, the electronic appliance is currently even smaller. This restricts installation of the anode lead 30a' and the cathode lead 30b' at the same side. Generally, each of the anode lead 30a' or the cathode lead 30b' has a width of 5 10 mm. Therefore, the anode lead 30a' and the cathode lead 30b' positioned in the same side requires at least 10 mm width. Therefore, in this case, a lithium secondary battery with less than 10 mm width is not practical. Disclosure of Invention Technical Problem

[5] An object of the present invention is to provide a lithium secondary battery that does not involve uneven heat distribution during charge and discharge.

[6] Another object of the present invention is to provide a lithium secondary battery that does not substantially involve limitation on the width of the battery by a width of the lead. Technical Solution

[7] The objects and others which will be described in the detailed description of the present invention can be accomplishable by provision of a lithium secondary battery comprising: a rechargeable electrode assembly, a pouch equipped with a cavity into which the rechargeable electrode assembly is accommodated, an anode lead and a cathode lead that deliver current generated from the rechargeable electrode assembly to an outer circuit, wherein the anode lead and the cathode lead are oppositely projected from the pouch based on the electrode assembly.

[8] According to more preferred embodiment of the present invention, the rechargeable electrode assembly is comprised of a plurality of anode plates and a plurality of cathode plates in which each of the anode plates has one anode tap and each of the cathode plates has one cathode tap, and each of the anode plates and each of the cathode plates are alternatively arranged to each other and separated by a separator. [9] According to another preferred embodiment of the present invention, the separator is successively folded in a fixed one direction.

Advantageous Effects

[10] The lithium secondary battery having an anode lead and a cathode lead oppositely projected from a pouch provides the following advantages.

[11] (a) The lithium secondary battery of the present invention solves uneven or unbalanced heat distribution during charge/discharge of the battery. Inside the lithium secondary battery, uniform or balanced heat distribution is accomplished. This increases the safety of the battery. Specifically, this reduces the danger of explosion of the battery that may be caused by excessive heat unbalance.

[12] (b) The width of the lithium secondary battery of the present invention is not restricted by the presence of the lead. This facilitates fabrication of even smaller sized batteries. Further, when the width of the lithium secondary battery was set to a certain value, the lithium secondary battery of the present invention can accommodate even larger lead than the conventional ones. This ensures much enhanced flow of the current. The lithium secondary battery with higher capacity and higher output can be obtainable.

[13] (c) The lead can be positioned at the center of the electrode plate. This simplifies arrangement of the electrode plate on the separator. The conventional lithium secondary battery has the anode lead and the cathode lead on the same side. In the case, each of the anode plate (or the cathode plate) should have two different configurations on the separator. To the contrary, the lithium secondary battery of the present invention makes it possible to be arranged as only one configuration.

[14] (d) The lithium secondary battery folded in a fixed one-direction has enhanced characteristic in terms of life cycle and charge/discharge capability. Brief Description of the Drawings

[15] Fig. 1 is a perspective view showing a preferred embodiment of the lithium secondary battery, in accordance with the present invention.

[16] Fig. 2 is a cross-sectional view showing a preferred embodiment of the lithium secondary battery, in accordance with the present invention.

[17] Fig. 3 is a resolved cross-sectional view showing a preferred embodiment of the lithium secondary battery, in accordance with the present invention.

[18] Fig. 4 is a perspective view showing a preferred embodiment of the electrode assembly used for the lithium secondary battery of the present invention.

[19] Fig. 5 is a cross-sectional view showing a conventional continuous type lithium secondary battery.

[20] Fig. 6 is a perspective view showing a typical conventional lithium secondary battery. Mode for the Invention

[21] Referring the accompanied drawings, the present invention will be more fully illustrated.

[22] Fig. 1 is a perspective view showing a preferred embodiment of the lithium secondary battery, in accordance with the present invention. Fig. 2 is a cross-sectional view showing a preferred embodiment of the lithium secondary battery, in accordance with the present invention. And Fig. 3 is a resolved cross-sectional view showing a preferred embodiment of the lithium secondary battery, in accordance with the present invention. As shown in Figs. 1 to 3, the lithium secondary battery of the present invention 1 comprises a pouch 20 having a cavity 22, an electrode assembly 10 accommodated into the cavity 22, an anode lead 30a and a cathode lead 30b oppositely projected from the pouch 20 base on the electrode assembly 10.

[23] In this case, the electrode assembly 10 is comprised of a plurality of anode plates

12a and a plurality of cathode plates 12b in which each of the anode plates 12a and each of the cathode plates 12b are separated by a separator 14 and alternatively stacked each other. Herein, each of the anode plates 12a has only one anode tap 16a, and each of the cathode plates 12b has only one cathode tap 16b. In a stacked electrode assembly 10, the anode taps 16a of the anode plates 12a are overlapping one another and the cathode taps 16b of the cathode plates 12b are also overlapping one another, as specifically exemplified in Fig. 4. The anode taps 16a and cathode taps 16b overlapping one another are each independently subjected to tap treatment, and then integrated each independently. Details of the tap treatment are described in Korean published patent No. 2003-95519 and Korean patent application No. 2004-82841.

[24] To the integrated anode taps 16a and cathode taps 16b, an anode lead 30a and a cathode lead 30b are each independently connected to deliver current from the electrode assembly 10 to an outer circuit or to charge the electrode assembly 10 with aid of an outer power source. Herein, the most important distinguishing point of the present invention is that the anode lead 30a and cathode lead 30b are positioned in parallel with the anode taps 16a and the cathode taps 16b and projected oppositely from the pouch 20 based on the electrode assembly 10. This arrangement avoids the uneven heat distribution during charge and discharge of the battery. As mentioned in the description of the prior art, the heat distribution is proportional to the distance from the lead. With the anode lead 30a and cathode lead 30b oppositely projected from the pouch 20, the uneven heat distribution on the anode plate 12a and the cathode plate 12b is offset, thereby relieving the uneven heat distribution on the electrode assembly 10.

[25] Further, with the opposite positioning of the anode lead 30a and cathode lead 30b based on the electrode assembly 10 does not involve limitation to the width of the battery by the presence of the lead. Suppose that each of the anode lead 30a and cathode lead 30b has a width of 5 mm. In this case, in order to arrange both the anode lead 30a and the cathode lead 30b in the same side of the pouch, which is shown in Fig. 6, the lithium secondary battery 1' should have at least above 10 mm width. Generally, it requires 13 mm width. According to the present invention, however, the battery having 6 mm width satisfies such a condition. Therefore, the width of the battery is not substantially limited by the anode lead 30a and the cathode lead 30b.

[26] The electrode plate (12a, 12b), but is not limited thereto, may be cut into a rectangular or circular shape, provided that the electrode plate (12a, 12b) has only one tap (16a, 16b). The shape of the electrode plate (12a, 12b) can be changed according to the desired form of the final electrochemical cell. The rectangular battery is typically used in PDA or mobile phone. The electrode plate (12a, 12b) is manufactured by coating an electrode active material (a cathode active material or an anode active material) onto a current collector. Regarding energy density, double-sided coating is preferable. Preferred cathode and anode active materials are exemplified in US Patent Nos. 5,837,015, 5,635,151 and 5,501,548. Specifically, a lithium transition metal oxide capable of intercalation/deintercalation of lithium ion, such as LiCoO 2 , LiMn 2 O 4 ,

LiNiO 2 or LiMnO 2 , can be mentioned as a cathode active material. As an anode active material, a material capable of intercalation/deintercalation of lithium ion, such as lithium metal, lithium alloy, carbon and graphite, can be mentioned. Preferably, the anode active material is carbon or graphite.

[27] The cathode or anode active material is dispersed into a suitable solvent, coated onto the surface of the current collector, and cut into a desired size to form the anode plate 12a or the cathode plate 12b, respectively. The electrode active material may be coated on one surface of the current collector. Preferably, it is coated on both surfaces of the current collector. Double-sided coating provides an increased discharge capacity per unit volume. With regard to preferred examples of the current collector, please refer toUS Patent Nos. 5,837,015, 5,635,151 and 5,501,548, which are incorporated herein by reference. According to the specific embodiment of the present invention, an aluminum thin plate and a copper thin plate were used as a cathode and anode current collector, respectively. Meanwhile, the electrode active material is, in general, coated on the surface of the current collector, in combination with a current conductive material that increases conductivity of the electrochemical cell and a binder that adheres both the electrode active material and the current conductive material to the current collector. The choice of the current conductive material and the binder would be readily accomplished in reference to the electrode active material, which is well known to a person of ordinary skill in the art to which the present invention pertains.

[28] The separator 14 has a role to prevent a direct electrical contact of the anode plate

12a with the cathode plate 12b and to provide pores for ion passage. Preferred examples are porous polyolefin films such as a polyethylene film or a polypropylene film, porous polyvinylidene fluoride films, porous hexapropylene fluoride films and porous polyethylene oxide films. The polyethylene film is being widely used in the art. As shown in Fig. 4, the separator 14 is successively folded in a fixed one direction. This increases the characteristics of the battery through tight fastening of the separator 14. The separator 14 may be folded in a zig-zag fashion, as described in KR 309,604 and 336,396, and JP H09-320637. However, the separator 14 is preferably folded in a fixed one direction, as shown in Fig. 4.

[29] The electrode assembly 10 with the anode lead 30a and the cathode lead 30b oppositely projected and extended in parallel from the taps (12a, 12b) is inserted into the cavity 22 of the pouch 20. An electrolyte solution is injected into the cavity 22 and the pouch 20 is sealed. In order to increase sealing of the anode lead 30a and the cathode lead 30b, heat-fused sheet may be additionally used, as shown in KR 274,867. In Figs. 2 and 3, unexplained reference numeral 50 is sealant.

[30] In addition, folding is performed in a fixed one-direction rather than in a zig-zag fashion. As thus, the disadvantages caused from the zig-zag folding can be avoid. For example, inconvenience of the folding process and difficulty for tight fastening of a separator can be solved. Besides the above advantages, the method reduces the scale of an facility required for adhering electrode plates and enables to efficiently utilize a working space, because the anode plates as well as the cathode plates are neighboring one another such that the portion to which the electrode plates are adhered can be reduced as much as 1/2, compared with KR 309,604, KR 336,396 and KR published patent 2002-93781. Further, the number of folding is reduced as much as 1/2, compared with KR 309,604, KR 336,396 and KR published patent 2002-93781, which increases the efficiency of the process. In addition, the lithium secondary battery fabricated by the method according to the present invention has highly enhanced charge/discharge characteristics because of stable interface by tight fastening of the separator sandwiched between the anode plate and the cathode plate during successive folding. And, the battery has no danger of an electrical short due to a complete separation between an anode plate and a cathode plate by a separator.

Claims

[1] A lithium secondary battery, comprising a rechargeable electrode assembly, a pouch equipped with a cavity into which the rechargeable electrode assembly is accommodated, an anode lead and a cathode lead that deliver current generated from the rechargeable electrode assembly to an outer circuit, wherein the anode lead and the cathode lead are oppositely projected from the pouch based on the electrode assembly.

[2] The lithium secondary battery as set forth in claim 1, wherein the rechargeable electrode assembly comprises a plurality of anode plates and a plurality of cathode plates in which each of the anode plates has one anode tap and each of the cathode plates has one cathode tap, and each of the anode plates and each of the cathode plates are alternatively arranged to each other and separated by a separator.

[3] The lithium secondary battery as set forth in claim 1, wherein the separator has a configuration folded in a fixed-one direction.

[4] The lithium secondary battery as set forth in claim 1, wherein the anode lead is parallel with the anode tap and the cathode lead is parallel with the cathode tap.

[5] The lithium secondary battery as set forth in claim 1, comprising a) the rechargeable electrode assembly comprising a plurality of anode plates and a plurality of cathode plates in which each of the anode plates has one anode tap and each of the cathode plates has one cathode tap, and each of the anode plates and each of the cathode plates are alternatively arranged to each other and separated by a separator; b) the pouch equipped with a cavity into which the rechargeable electrode assembly is accommodated; and c) the anode lead and the cathode lead that deliver current generated from the rechargeable electrode assembly to an outer circuit, wherein the anode lead and the cathode lead are oppositely projected from the pouch based on the electrode assembly and parallel with the anode tap and the cathode tap.