KR20080047635A - Secondary battery employed with electrode lead of ptc - Google Patents

Abstract

A secondary battery is provided to improve safety by preventing the explosion due to overcharge, overdischarge, falling and internal shortage and to increase the battery capacity to identical size. A secondary battery is provided with a battery case where an electrode assembly comprising a positive electrode, a separator and a negative electrode(300) is infiltrated in an electrolyte solution, wherein the positive electrode and the negative electrode of the electrode assembly are electrically connected to input/output terminals by an electrode lead(500), and the electrode lead is a PTC-type electrode lead. Preferably the PTC-type electrode lead has a thin and long hexahedral structure.

Description

Secondary Battery Embedding Electrode Lead of PCC {Secondary Battery Employed with Electrode Lead of PTC}

1 is a schematic diagram of a conventional cylindrical lithium secondary battery structure;

2 is a schematic diagram of a jelly-roll type electrode assembly used in a secondary battery according to one embodiment of the present invention;

3 is a perspective view of the PTC electrode lead of Figure 2;

4 is a schematic view of one end of the jelly-roll type electrode assembly used in the secondary battery according to another embodiment of the present invention;

FIG. 5 is an exploded perspective view of a square battery including the electrode assembly of the jelly-roll of FIG. 4.

The present invention relates to a secondary battery including an electrode lead of a PTC element, and more particularly, an electrode assembly having a positive electrode / separation membrane / cathode structure is embedded in a battery case in a state in which an electrolyte is impregnated, and the positive electrode of the electrode assembly. Alternatively, the negative electrode relates to a secondary battery electrically connected to an input / output terminal through an electrode lead made of a PTC element.

As the development and demand for mobile devices increases, the demand for secondary batteries as an energy source is increasing rapidly. Among the secondary batteries, a lot of researches have been conducted and commercialized on lithium secondary batteries having high energy density and high discharge voltage. It is widely used.

However, in the conventional lithium secondary battery, when a large current flows within a short time due to overheating, overcharge, external short circuit, nail penetration, local crush, etc., the battery is heated by IR heating. Risk of ignition / explosion. When the temperature of the battery rises, the reaction between the electrolyte and the electrode is accelerated, and as a result, heat of reaction is generated, which further increases the temperature of the battery, which in turn accelerates the reaction between the electrolyte and the electrode. Thus, the temperature of the battery rises rapidly, which in turn accelerates the reaction between the electrolyte and the electrode. Due to such a vicious cycle, a thermal runaway phenomenon in which the temperature of the battery rises rapidly occurs, and when the temperature rises to a certain level or more, the battery may ignite.

In addition, as a result of the reaction between the electrolyte and the electrode, gas is generated to increase the battery internal pressure, and when the pressure rises above a certain pressure, the lithium secondary battery explodes. The risk of ignition or explosion can be said to be the most fatal disadvantage of lithium secondary batteries.

Therefore, the lithium secondary battery includes various safety devices that can effectively control the battery when it is in an abnormal operating state such as an overcurrent state or a high temperature state.

Among them, a PTC (Positive Temperature Coefficient) element is electrically connected between an electrode assembly of a battery cell and an external input / output terminal, and maintains a low resistance at a temperature in a normal operating state, and flows a current, such as overcurrent or high temperature. In an abnormal state, the resistance increases rapidly with temperature rise, and only a small amount of current flows, thereby suppressing an increase in battery internal pressure due to overheating.

1 schematically shows a structure of a typical cylindrical lithium secondary battery.

Referring to FIG. 1, the secondary battery 10 includes a cylindrical can 20, an electrode assembly 30 accommodated in the can 20, and a cap assembly 40 coupled to an upper portion of the can 20. It is.

The electrode assembly 30 has a structure that is wound in a jelly-roll shape with a separator 33 interposed between the positive electrode 31 and the negative electrode 32, and the positive electrode lead 34 is attached to the positive electrode 31. A negative electrode lead (not shown) is attached to the negative electrode 32, and is connected to the lower end of the can 20.

The cap assembly 40 includes an upper cap 41 that forms a positive electrode terminal, a PTC element 42 that blocks a current by greatly increasing battery resistance when the temperature inside the battery increases, and blocks a current or a gas when the pressure increases inside the battery. A safety vent 43 for exhausting the air, an insulating member 44 for electrically separating the safety vent 43 from the cap plate 45 except for a specific portion, and a positive terminal 34 connected to the positive electrode 31. The cap plate 45 which is present is structured to be sequentially stacked.

As such, the safety devices including the PTC device 42 must maintain electrical connection with the electrode terminals and at the same time maintain electrical insulation with other parts of the battery cell. Therefore, in order to configure such a connection form, a plurality of insulating mounting members are required and have a disadvantage in that the assembly process of the battery is complicated.

In addition, in the above structure, since the electrode assembly inside the battery case and the PTC element mounted on the cap assembly at the top of the battery case are separated from each other, it is difficult to accurately detect the actual temperature of the battery. There is a problem in that the current blocking reaction rate of the drop does not prevent the risk of explosion of the battery in advance.

In this regard, Korean Patent Application Publication No. 2006-0027278 discloses a pouch-type secondary battery in which an electrode assembly having a separator interposed between a positive electrode and a negative electrode is stored, the protective circuit board for controlling charging and discharging and an electrode housed inside a battery case. A structure including a connecting lead portion for electrically connecting an assembly and a positive temperature element material layer between an upper conductive film and a lower conductive film is disclosed, and Japanese Patent Application Laid-Open No. 2004-228044 discloses a protection attached to a battery case. Disclosed is a structure in which a temperature protection device is provided at a lower end of a circuit board so that the temperature protection device is directly connected to the electrode lead.

However, the above techniques also have to install a separate temperature protection device (PTC device) between the protection circuit board and the electrode assembly, the manufacturing process is complicated, the temperature during the heating of the electrode assembly due to overcharge, over-discharge and internal short circuit There is still a problem that it is difficult to expect a rapid response of the protective device (PTC device).

Therefore, there is a high need for a technology capable of reducing the number of parts mounted on the top of the battery cell to simplify the manufacturing process and also improving the safety by quickly detecting the exothermic reaction inside the battery.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After extensive research and various experiments, the inventors of the present application implement a simple internal structure by reducing the number of parts of a battery when the electrode lead connected to the uncoated portion of the electrode sheet of the cylindrical secondary battery is formed of a PTC element. It is possible to shorten the manufacturing process, and because the PTC device is directly welded to the electrode sheet to confirm the advantage that the actual temperature of the electrode sheet is accurately transferred to significantly improve the safety of the battery and to complete the present invention.

In order to achieve the above object, the secondary battery according to the present invention, the electrode assembly of the positive electrode / separator / cathode structure is embedded in the battery case in the state impregnated with the electrolyte, the positive electrode and the negative electrode of the electrode assembly through the electrode lead It is electrically connected to the input / output terminal, and the electrode lead is composed of a PTC element ('PTC electrode lead').

As described above, the PTC device is typically mounted outside the cell as a separate module or substrate. Therefore, in the process of mounting the PTC element outside the cell, a separate module or substrate must be manufactured, space for mounting the module or substrate is required, and a difficult coupling process with the cell such as welding must be performed. Many problems are caused.

However, in the present invention, by using the electrode lead made of the PTC element, the above problems can be solved, and abnormal operation of the battery can be quickly detected without causing performance degradation of the battery. Can improve. In addition, by reducing the number of parts and the compact internal structure, the internal space of the battery can be utilized to the maximum, and the capacity of the battery can be increased compared to the same standard.

An electrode assembly in which a battery reaction occurs in a secondary battery generally has a structure in which an electrolyte solution is impregnated into a cathode plate coated with a cathode active material, an anode plate coated with an anode active material, and a separator. The electrode assembly of the secondary battery is classified into a jelly-roll type (wound) electrode assembly and a stacked type (laminated) electrode assembly according to its structure. Accordingly, the rectangular battery is manufactured by storing the jelly-roll type electrode assembly or the stacked electrode assembly in the rectangular metal case, and the cylindrical battery is manufactured by storing the jelly-roll type electrode assembly or the stacked electrode assembly in the cylindrical metal case.

The electrode assembly according to the present invention is not particularly limited as long as it is a structure that forms a positive electrode and a negative electrode by interconnecting a plurality of electrode tabs, and may be formed in a jelly-roll structure in one preferred example. The jelly-roll type electrode assembly has a structure in which a positive electrode and a negative electrode manufactured by applying an electrode active material to both sides of a long sheet metal foil are wound in a state with a separator interposed therebetween. According to the invention, such an anode or cathode is electrically connected to the cap assembly (structure including the top cap) and the metal can, respectively, via a PTC electrode lead.

In another preferred embodiment, the electrode assembly may have a stacked or stacked / folding structure, and the PTC electrode lead may be welded to the electrode tabs of the electrode assembly. Details of the electrode assembly of the stack / foldable structure are disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059, and 2001-0082060, which are described in the context of the present invention. Incorporated by reference.

In such a stack type or stack / fold type electrode assembly, the PTC type electrode lead is a group of electrode plates (A electrode group) to which a predetermined number of electrode tabs are coupled, or another group of electrodes to which the other electrode tabs are coupled. It is connected between the plates (B electrode group), the PTC electrode lead may be electrically connected to the A electrode group or B electrode group. Specifically, the PTC-type electrode leads are positioned between the electrode tabs of the A electrode group or the electrode tabs of the B electrode group, so that the internal short circuit due to the movement of the electrode assembly or the compression or penetration of the needle body when the external shock is applied. When the battery cell is overheated due to an internal short circuit or the like, the PTC element blocks the energization of the A electrode group or the B electrode group, thereby preventing a large amount of current from flowing.

This is only a difference in the connection position of the PCT element, and operates by the same principle that the conventional PCT element completely shuts off the electricity supply to the external input and output terminals of the battery cell, the operation of the battery cell in an abnormal operation state of the battery The battery current can be secured by greatly reducing the amount of current carrying.

In one preferred embodiment, the PTC electrode lead is a thin hexahedral structure as a whole, it may be made of a structure in which one connecting plate is extended to one side of the PTC body, and another connecting plate is extended to the other side. In other words, the PTC body is made of a rectangular polymer composite, and a connecting plate made of a metal plate is attached to the top and bottom of the PTC body, respectively.

For example, in the case of a cylindrical battery, one of the connecting plates may be electrically connected to the positive electrode plate or the negative electrode plate, and the other connecting plate may be electrically connected to the cap assembly or the metal can. In the case of the square battery, one of the connection plates may be electrically connected to the positive electrode plate or the negative electrode plate, and the other connection plate may be electrically connected to the metal can or the top cap.

Preferably, the outer surface of the PTC electrode lead except for the connection portion may be a structure wrapped with a sealing member. Specifically, in the PTC type electrode lead, the connecting plate extending from one side of the PTC main body is welded to the uncoated portion of the electrode current collector, and the connecting plate extending from the PTC main body to the other side includes a cap assembly, a top cap, and a metal can. It is welded to the back, and the rest of the connecting plate except these welding parts and the PCT body are wrapped with a sealing member, so that the two connecting plates contact the plain part of the current collector, the cap assembly, the top cap, etc. at the same time, so that they Can be prevented from flowing.

The connecting plates described above are not particularly limited as long as they are conductive materials, but nickel materials are particularly preferable.

In the present invention, the PTC electrode lead may be connected to at least one of the positive electrode and the negative electrode. In general, when an object such as a needle or the like presses or penetrates the battery from the outside, a short circuit is caused by contact between the positive electrode and the negative electrode, and the internal temperature of the battery rapidly increases due to the reaction of the electrode active materials during such a short circuit. In particular, since a cathode active material such as lithium transition metal oxide having low electrical conductivity generates a lot of heat during a short circuit, it may lead to ignition or explosion, and therefore, it is preferable to be connected to a cathode having a high possibility of abnormal heat generation.

However, of course, the PTC type electrode lead can be connected to the cathode.

The battery according to the present invention is not particularly limited as long as it has the internal structure as described above, and may be preferably applied to the lithium secondary battery as described above.

Hereinafter, although described with reference to the drawings according to an embodiment of the present invention, this is for easier understanding of the present invention, the scope of the present invention is not limited thereto.

Figure 2 shows a schematic diagram of the structure before the winding of the jelly-roll type electrode assembly used in the secondary battery according to an embodiment of the present invention.

Referring to FIG. 2, the jelly-roll type electrode assembly 100 is manufactured by connecting the PTC electrode leads 500 to one ends of the positive electrode plate 300 and the negative electrode plate 200, respectively, and winding them from right to left in the direction of the arrow. do. The positive electrode type PTC lead 500 protrudes above the electrode assembly and is welded to the cap assembly, for example in a cylindrical cell. On the other hand, the PTC-type electrode lead 510 of the cathode protrudes below the electrode assembly and is welded to the bottom inner surface of the metal can.

3 is a perspective view of the PTC electrode lead of FIG. 2.

Referring to FIG. 3, the PTC electrode leads 500 are attached with metal plates 520 and 530, which are connecting plates, respectively, attached to upper and lower ends of the PTC body 510, which is a rectangular polymer composite exhibiting PTC characteristics. It consists of a structure. In addition, the remaining portions of the metal plates 520 and 530 except for the welding portions A and B and the outer surface of the PTC body 510 are surrounded by an insulating sealing member 540. As the sealing member 540, for example, a heat shrinkable tube of an electrically insulating material may be used.

4 is a schematic view of one end of the jelly-roll type electrode assembly used in the secondary battery according to another embodiment of the present invention. In FIG. 4, the shape of the jelly-roll electrode assembly before winding round is illustrated for convenience of description.

Referring to FIG. 4, the jelly-roll type electrode assembly has the active material 320 disposed on both surfaces of the current collector (copper foil 310), similarly to a positive electrode (not shown) on which the active material is coated on both surfaces of the current collector (aluminum foil). It consists of a structure in which a separator (not shown) is interposed between the coated cathode 300. In order to prevent lithium ions from being precipitated as lithium metal, the negative electrode 300 is made somewhat larger than the positive electrode, and the separator is made larger than the positive electrode and the negative electrode 300.

An end portion of the cathode 300 is not coated with an active material, and thus, an uncoated portion 330 in which the copper foil 310 is exposed is formed. A PTC-type electrode lead 500 is welded to the uncoated portion 320. have.

The connection plate 530 extending from the PTC electrode lead 500 to one side of the PTC main body is welded to the negative electrode current collector uncoated part 330 and electrically connected thereto, and extends from the PTC main body to the other side. Part of the outer surface of the connecting plate 520 is wrapped with a sealing member 540 such as a heat shrinkable tube, thereby preventing the connecting plate 520 and the negative electrode current collector uncoated portion 330 from contacting.

FIG. 5 schematically illustrates an exploded perspective view of a rectangular battery including the jelly-roll electrode assembly of FIG. 4.

Referring to FIG. 5, in the prismatic battery, the jelly-roll electrode assembly 101 of FIG. 4 is embedded in a prismatic metal can 500, and a protruding electrode terminal (eg, a negative electrode) is formed on an open top of the can 500. Terminal: 620 has a structure that is coupled to the top cap 600 is formed.

The negative electrode of the electrode assembly 101 is electrically connected to the lower end of the negative electrode terminal 620 on the top cap 600 through the PTC electrode lead 500, such a negative electrode terminal 620 by the insulating member 624 It is insulated from the top cap 600. On the other hand, another electrode (eg, anode) of the electrode assembly 101 is electrically connected to the top cap 600 whose electrode lead 334 is made of a conductive material such as aluminum, stainless steel, or the like. It forms the positive terminal by itself.

In addition, except for the PTC-type electrode lead 620 which is a negative electrode terminal and the electrode lead 334 which is a positive electrode terminal, in order to ensure the electrical insulation state of the electrode assembly 101 and the top cap 600, the square case 500 and the electrode After inserting the sheet-shaped insulating member 650 between the assembly 101, and covers the top cap 600, and joining them by welding along the contact surface of the top cap 600 and the case 500. Then, the electrolyte is injected through the electrolyte injection hole 610 and then welded and sealed, and a battery is manufactured by applying a welding site with epoxy or the like.

Although described above with reference to the drawings according to an embodiment of the present invention, those of ordinary skill in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the electrode lead made of the PTC element in the secondary battery according to the present invention is directly connected to the negative electrode plate or the positive electrode plate inside the battery, so that the PTC element can react more sensitively to the temperature change of the battery. In addition, by unifying existing electrode leads and PTC elements into a single PTC-type electrode lead, the internal space of the battery can be utilized to the maximum, thereby simplifying the manufacturing process and greatly increasing the battery capacity compared to the same standard.

Claims (8)

The electrode assembly of the anode / membrane / cathode structure is embedded in the battery case in the state in which the electrolyte is impregnated, the anode and the cathode of the electrode assembly are electrically connected to the input / output terminal through the electrode lead, and the electrode lead is a PTC device. ('PTC type electrode lead') a secondary battery characterized by consisting of. The electrode assembly of claim 1, wherein the electrode assembly is a jelly-roll having a structure in which a cathode sheet and an anode sheet are wound with a separator interposed therebetween, and the PTC electrode lead is formed on an uncoated region where an active material of the electrode sheet is not coated. A secondary battery, which is welded. The secondary battery of claim 1, wherein the electrode assembly has a stack type or a stack / fold type structure, and the PTC type electrode lead is welded to electrode tabs of the electrode assembly. The secondary battery according to claim 1, wherein the PTC electrode lead has a thin, long hexahedral structure as a whole, and has a structure in which a connection plate extends on one side of the PTC body and another connection plate extends on the other side. . The secondary battery of claim 4, wherein an outer surface of the PTC electrode lead is surrounded by a sealing member except for an electrical connection portion. The secondary battery of claim 4, wherein the connection plates are made of nickel. The secondary battery according to claim 1, wherein the PTC electrode lead is connected to at least one of a positive electrode and a negative electrode. The secondary battery of claim 1, wherein the battery is a lithium secondary battery.

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