KR101367751B1 - secondary battery and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a secondary battery, comprising: an electrode assembly having a first electrode plate, a second electrode plate, and a separator; A secondary battery having a case having an accommodating portion together with an electrode assembly, the secondary battery comprising: a first lead connected to a first tab connected to a first electrode plate and a second tab connected to a second electrode plate; A second lead, which may be connected to the first lead; And a connection / separation member electrically connecting the first lead and the second lead and electrically separating the first lead and the second lead when the internal pressure of the case increases.

Secondary battery, lead, foaming agent, welding, blocking

Description

Secondary battery and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery and a method of manufacturing the same, and to a secondary battery and a method of manufacturing the same having an improved structure to prevent explosion or ignition caused by an increase in internal pressure due to anomalous phenomenon.

In general, with the development of technology and increasing demand for mobile devices, the demand for secondary batteries is also rapidly increasing. Among them, lithium (ion / polymer) secondary batteries having high energy density, high operating voltage, and excellent storage and life characteristics are various. It is widely used as an energy source of various electronic products as well as mobile devices.

However, since various combustible materials are built into the secondary battery, the battery body swells when there is an abnormal phenomenon such as overcharging, overcurrent, other physical external shock, or neglect at high temperature, and thus, there is a risk of overheating and explosion, thereby making the safety inferior. There are disadvantages. Therefore, when the battery operates abnormally, for example, PTC (Positive Temperature Coefficient) element, protection, forcibly discharging the electrolyte inside the battery to the outside or effectively controlling abnormal conditions such as overcharge, overcurrent Safety devices, such as a protection circuit module (PCM), are connected to the battery cell.

However, even if these safety measures are taken, the problem of malfunction still remains in the secondary battery, and if a problem occurs in the circuit, the probability of occurrence of such malfunction is higher. Therefore, there is a need for an improved technology that can solve this problem.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above problems, and in a secondary battery such as a lithium ion batter, a lead attached to a tab for connecting a battery and an external device has a double structure, and the secondary battery is in use. It is an object of the present invention to provide a secondary battery and a method of manufacturing the same, in which the stability of the secondary battery can be improved by disconnecting the lead of such a double structure when the temperature rises due to an abnormal phenomenon.

In order to achieve the above object, a secondary battery according to a preferred embodiment of the present invention, an electrode assembly having a first electrode plate, a second electrode plate, and a separator; A secondary battery having a case having a receiving part for receiving an electrolyte together with the electrode assembly, comprising: a first lead connected to a first tab connected to the first electrode plate and a second tab connected to the second electrode plate; A second lead that may be connected to the first lead; And a connection / separation member electrically connecting the first lead and the second lead and electrically separating the first lead and the second lead when the internal pressure of the case increases.

Preferably, the connection / disconnection member comprises: a foaming agent interposed between the first lead and the second lead; An adhesive for bonding between the first lead and the second lead to wrap around the blowing agent; And a weld formed between the first lead and the second lead.

Preferably, the weld is formed by spot or ultrasonic welding.

Preferably, the weld is formed at a pair of edges of the end of the first lead or the second lead.

Preferably, the ends of the first lead and the second lead have bent portions that face each other, and the blowing agent is applied between the bent portions.

Preferably, the width of the first lead is greater than the width of the second lead.

Preferably, the adhesive is applied to corner portions of the first lead and the second lead.

A secondary battery manufacturing method according to a preferred embodiment of the present invention for achieving the above object, (a) preparing a first lead and a second lead; (b) applying a blowing agent to the end of the first lead; (c) disposing the blowing agent so that the end of the second lead is covered and welding the first lead and the second lead; (d) attaching the first lead and the second lead with an adhesive; (e) integrating the tabs of the electrode plate with the cathode electrode plate / separator / anode electrode plate sequentially arranged; (f) connecting an end of the tab to the first lead to which the second lead is attached to form an electrode assembly; And (g) sealingly storing the electrode assembly together with the electrolyte in the case.

Preferably, the step (c) includes spot or ultrasonic welding the corner portions of at least ends of the first lead and the second lead.

Preferably, after the step (c) pressing the first lead and the second lead around the blowing agent; And after the step (d), releasing the pressure after the adhesive is cured.

Preferably, the step (a) further comprises the step of bending the ends of the first lead and the second lead to form a bent portion, in the step (b) is applied to the blowing agent between the bent portion.

The secondary battery and the manufacturing method thereof according to the present invention has the following effects.

First, because the two leads are connected by the connecting portion, the secondary battery does not affect the performance of the secondary battery within the normal operating temperature range, but the abnormality is caused by the foaming agent foamed at a high temperature and the adhesive rapidly deteriorating the adhesive force at a high temperature. When the internal temperature of the secondary battery rises due to the occurrence, the two leads connected by the expansion of the blowing agent and the weakening of the adhesive force are separated to block the electric flow inside the secondary battery, thereby improving the stability of the battery.

Second, instead of connecting the two leads only with an adhesive, spot or ultrasonic welding of the leads can block the possibility of increasing contact resistance.

Hereinafter, a rechargeable battery and a method of manufacturing the same according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view schematically illustrating a rechargeable battery according to a preferred embodiment of the present invention, FIG. 2 is a plan view illustrating a first lead portion of FIG. 1, and FIG. 3 is a first lead and a first lead of FIG. 1. 2 is a plan view of the connecting portion of the two leads, and FIG. 4 is a side view of FIG. 3.

1 to 4, a secondary battery 100 according to a preferred embodiment of the present invention includes a first electrode plate 12 (see FIG. 2), a second electrode plate (not shown), and a separator 14. It is provided with the case 20 which has the electrode assembly 10 provided, and the accommodating part 22 with which the electrolyte solution is accommodated with the electrode assembly 10.

In general, secondary batteries may be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries according to the type of separator and electrolyte used, and may be classified into cylindrical, square coin, and pouch types according to their shape. It may be classified into a bulk type and a thin film type according to the size. The secondary battery 100 according to a preferred embodiment of the present invention is particularly suitable for a so-called pouch type battery in which a positive electrode plate and a negative electrode plate are alternately stacked by a polyethylene separator. Therefore, the secondary battery 100 to be described below means a pouch-type lithium secondary battery, the structure and manufacturing method of such a battery is well known in the art, its detailed description is omitted.

The secondary battery 100 according to the preferred embodiment of the present invention includes a first tab 42 and a second tab 44 formed integrally with the first electrode plate 12 and the second electrode plate, respectively, The first lead 30 welded to the ends of the first tab 42 and the second tab 44, the second lead 50 which may be connected to the first lead 30, the first lead 30 and the second lead. The lead 50 is electrically connected to each other, and has a connection / separation member 60 capable of electrically separating the first lead 30 and the second lead 50 when the internal pressure of the case 20 increases.

The electrode assembly 10 has a structure in which a so-called pouch-type battery in which electrode plates are stacked, for example, a first electrode plate 12 / separator 14 / a second electrode plate is sequentially arranged. Here, the first electrode plate 12 means an anode, and the second electrode plate means a cathode. Typically, in the electrode assembly 10, the first electrode plate 12 and the second electrode plate have a structure in which an active material is coated on at least one surface of the current collector. In the case of the current collector, the positive electrode current collector is made of aluminum (Al), the negative electrode current collector is made of copper (Cu), and the positive electrode current collector or the negative electrode current collector is generally manufactured to a thickness of 3 to 500 μm.

Since the first tab 42 and the second tab 44 are formed integrally with the corresponding first electrode plate 12 and the second electrode plate, respectively, the first tab 42 and the second tab 44 are formed of the corresponding first electrode plate 12 and the second electrode plate. It is the same as the material and the active material is not coated on the surface. Accordingly, the secondary battery 100 having a structure in which a plurality of electrode plates are stacked is connected to the corresponding first leads 30 by integrating tabs having the same number and number of electrode plates at the same polarity at substantially the same positions.

The first lead 30 is attached to the corresponding tabs 42 and 44 and the second lead 50 uses a conventional conductive material known in the art as a kind of terminals connected to an external device. The ends of the first lead 30 and the second lead 50 may be arranged in parallel with each other, but in this embodiment, the ends of the first lead 30 and the second lead 50 are substantially in the length direction thereof. The bent portions (32) and (52) are bent to protrude vertically. The bends 32 and 52 are formed such that the first lead 30 and the second lead 50 face each other to form a predetermined space, and the blowing agent 62 is positioned in the space. In addition, although the width of the first lead 30 and the second lead 50 may be configured to be equal to each other, in the present embodiment, the width of the first lead 30 connected to the tabs 42 and 44 is zero. It is provided slightly larger than the width of the two leads 50. This is for the first lead 30 connected to the tabs 42 and 44 to function as the main of the overall lead structure. Of course, the second lead 50 may be larger than the width of the first lead 30.

The connecting / disconnecting member 60 includes a blowing agent 62 interposed between the first lead 30 and the second lead 50, and the first lead 30 and the second lead to surround the foaming agent 62. And an adhesive 64 for adhering between the 50, and a weld 66 formed between the first lead 30 and the second lead 50.

The blowing agent 62 employs a well-known blowing agent which is foamed at about 90-130 ° C. and expands while ejecting nitrogen and carbon dioxide. The blowing agent 62 is intended to separate the first lead and the second lead 50 from each other by foaming and expanding when an abnormal situation occurs due to an increased internal pressure during use of the secondary battery 100.

The welding portion 66 is preferably formed by spot welding, and may be formed at a pair of corners of the end of the first lead 30 or the second lead 50 and may be formed at both edges. It may be. In this embodiment, the spot or ultrasonically welded to the end edge of the second lead 50 and the corresponding first lead 30 is shown. This welding portion 66 is to reduce such electrical resistance because there is an electrical resistance at the contact surface when the two metals are bonded only with an adhesive. Of course, in order to reduce the electrical resistance, when bonding the adhesive, the adhesive may be attached while the two metals are tightly tightened, and the tightening between the two metals may be released. Since this can be a problem in this embodiment is to solve such electrical resistance problem through the weld 66. Therefore, if there are too many welds 66, the two leads 30, 50 may be incompletely separated when separated by the blowing agent 62 of the separating / adhesive member 60, so that the minimum In order to connect the two leads 30 and 50 with force, it is preferable that the welding part 66 is performed by spot or ultrasonic welding in a predetermined number and a predetermined place.

The adhesive 64 is applied to corner portions of the first lead 30 and the second lead 50, and is applied in four directions around the foam 62. That is, it is preferable that the adhesive agent 64 is formed in one edge portion of the first lead 30 and the second lead 50. The adhesive preferably uses a conductive adhesive in which a conductive paste component is mixed with a conventional adhesive material.

Hereinafter, a secondary battery manufacturing method according to a preferred embodiment of the present invention.

First, the first lead 30 and the second lead 50 are prepared, respectively. The first lead 30 and the second lead 50 have one overall lead function of the secondary battery by such a connection where their ends are connected to each other and are separated from each other when necessary. Meanwhile, the ends of the first lead 30 and the second lead 50 are provided with bent portions 32 and 52 protruding a predetermined length in a direction substantially perpendicular to the length direction thereof. In addition, as described above, the width of the first lead 30 is larger than the width of the second lead 50.

Then, as shown in FIG. 2, the blowing agent 62 is applied between the ends of the first lead 30, preferably between the bends 32 and 52. The blowing agent 62 to be applied is applied to have a predetermined length in the width direction of the first lead 30 and to have a predetermined width in the longitudinal direction of the first lead 30, and the thickness thereof is two leads 30 when an abnormal phenomenon occurs. It is preferable to apply enough to separate the (50).

Next, as shown in FIGS. 3 and 4, the second lead 50 is nested in the first lead 30 so that the end of the second lead 50 is covered with the blowing agent 62.

Subsequently, after pressing the first lead 30 and the second lead 50 around the foaming agent 62, the pressure is released after the adhesive 64 is cured.

Next, the first lead 30 and the second lead 50 are welded (spot or ultrasonically welded). In this case, the welding is preferably formed at the end edge portion of the second lead 50.

Next, the part (four places) where the edge of the 1st lead 30 and the 2nd lead 50 meets is bonded by an adhesive agent.

Next, the tabs 42 and 44 of the electrode plate are integrated in a state where the cathode electrode plate / separator / anode electrode plate is sequentially arranged, and the ends of the tabs 42 and 44 are connected to the second lead 50. 1 is welded with the lead 30 to form an electrode assembly.

Finally, after the electrode assembly 10 is accommodated in the case 20 together with the electrolyte, the case 20 is sealed.

Although the present invention has been described with respect to a so-called 'unidirectional lead' in which the positive electrode and negative electrode leads are all formed at one end of the electrode assembly in the electrode assembly, the positive electrode lead and the negative electrode lead exist in positions symmetrical or orthogonal to each other The present invention is not limited thereto.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. And various modifications and variations are possible within the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given above, serve to further the understanding of the technical idea of the invention, And should not be construed as interpretation.

1 is an exploded perspective view schematically illustrating a rechargeable battery according to an exemplary embodiment of the present invention.

FIG. 2 is a plan view showing an extract of the first lead portion of FIG. 1. FIG.

3 is a plan view of a connection portion of the first lead and the second lead of FIG. 1.

Figure 4 is a side view of Figure 3;

Claims (10)

An electrode assembly having a first electrode plate, a second electrode plate, and a separator; In the secondary battery having a case having a receiving portion for storing an electrolyte solution together with the electrode assembly, First leads respectively connected to a first tab connected to the first electrode plate and a second tab connected to the second electrode plate; A second lead that may be connected to the first lead; And And a connection / separation member electrically connecting the first lead and the second lead and electrically separating the first lead and the second lead when the internal pressure of the case increases. The method of claim 1, The connection / disconnection member is: A blowing agent interposed between the first lead and the second lead; An adhesive for bonding between the first lead and the second lead to wrap around the blowing agent; And And a weld formed between the first lead and the second lead. 3. The method of claim 2, The welding unit is a secondary battery, characterized in that formed by spot or ultrasonic welding. 3. The method of claim 2, The welding unit is a secondary battery, characterized in that formed on a pair of corners of the end of the first lead or the second lead. 3. The method of claim 2, Ends of the first lead and the second lead has a bent portion bent to face each other, The foaming agent is characterized in that the blowing agent is applied between the bent portion. 3. The method of claim 2, The adhesive is a secondary battery, characterized in that applied to the edge portion of the first lead and the second lead. (a) preparing the first lead and the second lead (b) applying a blowing agent to the end of the first lead; (c) disposing the blowing agent so that the end of the second lead is covered and welding the first lead and the second lead; (d) attaching the first lead and the second lead with an adhesive; (e) integrating the tabs of the electrode plates with the cathode electrode plate / separator / anode electrode plate sequentially arranged; (f) connecting the first lead to which the second lead is attached to an end of the tab to form an electrode assembly; And (g) sealing the electrode assembly together with the electrolyte in the case; manufacturing method of a secondary battery. The method of claim 7, wherein The step (c) of the secondary battery manufacturing method comprising the step of spot or ultrasonic welding the edge of at least the end of the first lead and the second lead. 9. The method of claim 8, Pressing the first lead and the second lead around the blowing agent after the step (c); And After the step (d), further comprising the step of releasing the pressure after the adhesive is cured. The method of claim 7, wherein The step (a) further includes bending the ends of the first lead and the second lead to form a bent portion, The secondary battery manufacturing method, characterized in that in the step (b) the blowing agent is applied between the bent portion.

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