KR20120134341A - Secondary cell having improved adhesiveness at edges of electrode terminals - Google Patents

Abstract

PURPOSE: A secondary battery with the improved adhesion of an edge part of an electrode lead is provided to prevent phenomenon such as dielectric breakdown, the leakage of electrolyte due to cracks, etc. CONSTITUTION: A secondary battery in which an electrode assembly(30) with the structure of a positive electrode/separator/negative electrode is mounted in a pouch type battery case; electrode leads(60,70) connected to electrode taps(40,50) in the electrode assembly and in which an edge part is tapered to be gradually inclined in an angle of 100° or more; and a lead film composed to surround the electrode lead for simultaneously attaching the electrode lead to the battery case and insulating the same.

Description

Secondary cell having improved adhesiveness at edges of electrode terminals

The present invention relates to a secondary battery having improved adhesion of the edge portion of the electrode lead, and more specifically, to form an electrode tapered to gently incline the edge portion of the electrode lead more than 100 ° to hermetically adhere the electrode lead to the battery case The present invention relates to a secondary battery having improved adhesion between edge portions of leads and electrode leads, which can improve leakage preventing and moisture penetration of electrolyte between electrode leads and battery cases.

Secondary cells and storage batteries are devices that convert external electrical energy into chemical energy and store it, and then generate electricity when needed. The term "rechargeable battery" also means that the battery can be recharged several times.

Common secondary batteries include lead acid batteries, NiCd batteries, NiMH batteries, Li-ion batteries, and Li-ion polymer batteries.

Recently, with the rapid development of multimedia, mobile communication devices, portable electronic devices, and new information terminals with complex functions have been spread, and secondary batteries are keeping pace with the emergence of new batteries that require miniaturization, light weight, high capacity, and short charging time. Was developed.

Secondary batteries used in electronic devices include lead acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and lithium ion batteries (LIB, lithium). ion battery) and lithium polymer battery (LPB).

Recently, with the increase of portable devices requiring high performance, eco-friendly lithium ion secondary batteries, which have high energy density, no memory effect, and excellent cycle characteristics, have made up for the shortcomings of nickel-cadmium batteries or nickel-hydrogen batteries. .

As a result, research and development of large-scale high-power secondary batteries used in hybrid cars and electric vehicles as well as small secondary batteries such as mobile phones, PCs, personal digital assistants (DDAs), digital cameras, and camcorders are being actively conducted.

In accordance with the technological innovation of secondary batteries, the current era of the internal combustion engine based on automobile oil is gradually ended, and the era of electric motor power has started to enter. Rechargeable batteries are the most essential part of the era of electric motor power and represent the era of electric vehicles.

As the environmental awareness deepens, the hybrid (HEV) vehicle, which is being spotlighted as an eco-friendly vehicle, uses a large high-output secondary battery as an auxiliary power. High-power secondary battery maximizes the driving efficiency of gasoline engines by assisting the engine when the vehicle demands high output, ie when the vehicle starts or when climbing slopes and rapid acceleration, and it improves fuel efficiency more than twice compared to the existing cars and releases pollutant emissions. 50% reduction effect.

Secondary batteries provide both economic and environmental advantages over single-use primary batteries. The advantage is that it can be recharged several times, but it is more expensive than the primary battery and the chemicals and metals used in these cells are more toxic.

Secondary batteries are also attracting attention as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are proposed as solutions for air pollution of conventional gasoline and diesel vehicles using fossil fuels.

Representatively, there is a high demand for square secondary batteries and pouch type secondary batteries that can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and high energy density, discharge voltage, and output stability in terms of materials. There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

In addition, secondary batteries are classified according to the structure of the electrode assembly of the positive electrode / separator / cathode structure, typically a long sheet-shaped cathode and the cathode of the structure wound around the separator interposed- jelly- Roll (electrode) assembly, a plurality of anodes and negatives cut in a unit of a predetermined size, a jelly-roll (winding) electrode assembly of a structure wound around the separator interposed, a plurality of units of a predetermined size And a stack-folding electrode assembly having a structure in which bi-cells or full cells are wound, in which positive and negative electrodes are stacked with a separator interposed therebetween.

Recently, a pouch-type battery having a stacked or stacked / folding electrode assembly in a pouch-type battery case of an aluminum laminate sheet has attracted a lot of attention due to its low manufacturing cost, small weight, and easy shape deformation. Usage is gradually increasing.

1, the general structure of a typical representative pouch type secondary battery is schematically illustrated as an exploded.

The pouch type secondary battery 1 includes an electrode assembly 3 in which an anode and a cathode are insulated by a separator, electrode tabs 4 and 5 extending from the electrode assembly 3, and electrode tabs 4,. 5) electrode leads 6 and 7 welded to them, and a battery case 2 for receiving the electrode assembly 3.

The electrode assembly 3 is a power generator in which a positive electrode and a negative electrode are sequentially stacked in a state where a separator is interposed therebetween, and has an stacked or stacked / folding structure. The electrode tabs 4, 5 extend from each pole plate of the electrode assembly 30, and the electrode leads 6, 7 are for example welded to the plurality of electrode tabs 4, 5 extending from each pole plate. Each of them is electrically connected to each other, and part of the battery case 2 is exposed to the outside.

In addition, lead films 8 having excellent insulation properties are attached to upper and lower portions of the electrode leads 6 and 7 to increase the sealing degree with the battery case 2 and to secure the electrical insulation state. The battery case 2 is made of an aluminum laminate sheet, provides a space for accommodating the electrode assembly 3, and has a pouch shape as a whole.

The lead films 8 are attached to the electrode leads 6 and 7 of the pouch-type secondary battery 1 to be fused to each other by heat-sealing layers and heat of the upper 2a and lower sheet 2b of the battery case 2. It prevents the leakage of electrolyte in the secondary battery (1), prevents short circuit, and prevents water penetration.

However, the conventional lead film 8 has a thickness of about 0.15 mm and surrounds the electrode leads 6 and 7 as shown in FIG. 2A. The total thickness of the lead film 8 is about 0.6 mm. Since 7) is about 0.3 mm, as shown in FIG. 2B, the lead film 8 having a thickness of about 0.15 mm is broken at the corners, whereby a fine crack 9 may occur, causing the electrolyte to leak.

In addition, the edges of the electrode leads 6 and 7 are sharply formed at an angle of 90 ° or less, so that charges (for example, electrons e) are collected at the corners of the electrode leads 6 and 7 to insulate or insulate them from the edges. Insulation resistance, such as leakage current flows frequently occurred.

The technical problem of the present invention is the safety of various batteries and the battery due to problems such as leakage of electrolyte caused by the breakdown and cracks caused by the sharp edge of the lead film surrounding the edge of the electrode lead in a conventional pouch battery It is to solve the problems that impair life.

Accordingly, an object of the present invention is to provide a secondary battery having improved adhesion of the edge portion of the electrode lead that can prevent problems such as breakdown of the electrolyte generated by the edge portion of the electrode lead and leakage of the electrolyte due to cracking.

Another object of the present invention is formed by the tapered edge of the electrode lead is inclined at an angle of more than 100 ° with respect to the upper surface so that the lead film surrounding the edge of the electrode lead is gently bent attached to prevent cracks from leaking electrolyte solution It is to provide a secondary battery that improves the adhesion of the edge portion of the electrode lead that can prevent problems such as.

Another object of the present invention by sandblasting the edge portion of the electrode lead is formed to be tapered gently at an angle of more than 100 ° to form a rough surface of several micrometers to several tens of micrometers to lead to a sharp increase in the specific surface area lead at the corner portion It is to provide a secondary battery that improves the adhesion of the edge portion of the electrode lead to prevent the leakage of the electrolyte by remarkably improving the interface adhesion between the film and the conductor electrode.

In the present invention for achieving the above technical problem and the electrode lead is formed by tapering the edge portion gently inclined at an angle of 100 ° or more in a conventional secondary battery; And a lead film configured to surround the electrode lead and adhere to the case and to form insulation.

According to an embodiment of the present invention, an electrode assembly having a cathode / separation membrane / cathode structure is a secondary battery embedded in a pouch type battery case, and is connected to electrode tabs of the electrode assembly and adhered to the battery case by a lead film. An electrode lead formed by tapering the corner portion gently at an angle of 100 ° or more; The electrode lead is surrounded by a thickness thinner than 1/2 of the thickness of the electrode lead and adhered to the pouch case, and is composed of a lead film configured to form insulation at the same time.

According to one embodiment of the present invention, the left and right edges of the electrode lead are also formed so as not to have an angle, so that cracks due to sharpness are less likely to occur, and the phenomenon in which charge concentrates on the tip is also prevented.

According to one embodiment of the present invention, the tapered four corners of the electrode lead are sandblasted to improve the adhesion with the lead film, and the surface of the electrode lead is characterized in that the fine concavo-convex surface is formed.

The secondary battery according to the present invention in accordance with the between the innermost layer of the on-electrode lead and the lead film and the cell can improve the adhesion to a lead film by the fine uneven surface formed tapering edge portion of the electrode leads, and processing the sand blasting heat By maintaining the stability and sealability of the heat seal due to fusion, it is possible to prevent moisture from penetrating from the outside and leakage of the electrolyte inside.

1 is an exploded perspective view of a pouch-type secondary battery according to the prior art,
Figure 2a is an enlarged view of the edge of the electrode lead according to the prior art,
Figure 2b is a crack caused by the sharp bending of the lead film surrounding the edge of the electrode lead according to the prior art,
Figure 3a is a perspective view showing the structure of the electrode assembly of the pouch type secondary battery according to an embodiment of the present invention,
Figure 3b is a perspective view of the electrode assembly sealed in the battery case according to an embodiment of the present invention,
4 is a cross-sectional view taken along the line AA ′ of FIG. 3B to show an electrode lead and a lead film adhered to the electrode lead of the pouch type secondary battery according to one embodiment of the present invention;
5 is a cross-sectional view showing a cross section of the electrode lead of the pouch type secondary battery according to an embodiment of the present invention;
6 is a surface state sandblasted the edge portion of the electrode lead according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text.

It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a part or a combination thereof is described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

3A is a perspective view showing the structure of an electrode assembly of a pouch type secondary battery according to an embodiment of the present invention, and FIG. 3B is a perspective view of an electrode assembly sealed in a battery case according to an embodiment of the present invention. .

The pouch type secondary battery 10 according to the present invention is a secondary battery in which an electrode assembly 30 having a positive electrode / separation membrane / cathode structure is built in a pouch-type battery case 20, and an electrode tab of the electrode assembly 30 ( Electrode leads 60 and 70 connected to 40 and 50 and tapered at an angle of 100 ° or more to an edge portion bonded to the battery case 20 by the lead film 80; The electrode leads 60 and 70 are surrounded by a thickness thinner than 1/2 of the thickness of the electrode leads, and are bonded to the battery case 20 and formed of a lead film 80 configured to form insulation.

The electrode assembly 30 is a discharge / charge device in which an anode and a cathode are sequentially stacked in a state where a separator is interposed therebetween, and has a stack type or a stack / fold type structure. The positive and negative electrode tabs 40 and 50 extend from each of the electrode plates of the electrode assembly 30, and the electrode leads 60 and 70 correspond to the plurality of positive and negative electrode tabs 40 and 50 extending from the respective electrode plates. For example, each is electrically connected by welding, and a portion of the battery case 20 is exposed to the outside of the battery case 20 as illustrated in FIG. 3B.

3A and 3B, the pouch type secondary battery 10 includes an electrode assembly 30, electrode tabs 40 and 50 extending from the electrode assembly 30, and electrode tabs 40 and 50. And a battery case 20 accommodating the electrode leads 60 and 70 to be welded, and the electrode assembly 30.

Lead films 80 are attached to upper and lower portions of the electrode leads 60 and 70 to increase the sealing degree with the battery case 20 and to secure an electrical insulation state.

4 is a cross-sectional view illustrating a cross section taken along line AA ′ of FIG. 3B to show an electrode lead and a lead film adhered to the electrode lead of the pouch type secondary battery according to the exemplary embodiment of the present invention.

Referring to FIG. 4, the plurality of positive electrode tabs 40 and the negative electrode tabs 50 protruding from the positive electrode current collector of the electrode assembly 30 are, for example, in the form of a weld portion integrally coupled by welding. The anode lead 60 and the cathode lead 70 are respectively connected.

The positive lead 60 and the negative lead 70 have one end 61 and 71 welded to the positive electrode tab 40 and the negative electrode tab 50, respectively, and the opposite ends 62 and 72 are exposed. The lead film 80 is sealed by heat sealing in the battery case 20 with the interposed state.

5 is a cross-sectional view illustrating a cross section of an electrode lead of the pouch type secondary battery according to the exemplary embodiment of the present invention.

Since the positive lead 60 and the negative lead 70 according to the present invention have the same shape, only the positive lead 60 is shown and described here, but the same description can be made with respect to the negative lead 70. ) Will be omitted.

The anode lead 60 according to the present invention has a wide flat plate shape, but the corner portions 68a and 68d where the upper surface 63a and the upper left and right sides 64a and 65a meet each other have an obtuse angle of 100 ° or more, more preferably 130 ° or more. The left and right side surfaces 64a and 65a are gently inclined with respect to the upper surface 63a.

Similarly, the corner portions 68b and 68c where the lower surface 63b and the lower left and right sides 64a and 65a meet are formed at an obtuse angle of 100 ° or more, more preferably 130 ° or more, so that the lower left and right sides 64b with respect to the bottom surface 63b. , 65b) is formed to be inclined gently.

Accordingly, the four corner portions 68a, 68b, 68c, and 68d where the upper surface 63a and the upper left and right sides 64a and 65a and the lower surface 63b and the lower left and right sides 64b and 65b meet each other do not have sharp bending. Since the wedge does not act like a wedge, the lead film 80 adhered thereon is hardly cracked and does not generate charge concentration.

In addition, the left and right tip portions 66 and 67 are also formed so as not to be angled, so that cracks due to sharpness are less likely to occur and the phenomenon of concentration of charge in the attachment can be prevented.

The battery case 20 is composed of a multi-layer film and should be adhered to the electrode leads 60 and 70 to prevent leakage of the internal electrolyte solution. The innermost layer of the battery case 20 is adhesive to the electrode leads 60 and 70. In particular, it is necessary to have thermal adhesiveness.

In order to bond the lead films 60 and 70 to the innermost layer of the battery case 20 by applying heat to the electrode leads 60 and 70, the battery case ( Since the innermost layer of 20) is adhered by heat fusion, adhesion at the interface between the electrode leads 60 and 70 and the lead film 80 should be hermetically sealed.

Fig. 6 shows the surface state where the edge portion of the electrode lead according to the present invention is sandblasted.

Tapered four corner portions 68a, 68b, 68c, and 68d of the electrode leads 60 and 70 according to the present invention are sandblasted on the surface to improve adhesion to the lead film 80. Fine uneven surface is formed on the surface of (60, 70).

Therefore, as shown by sandblasting, fine uneven surfaces of several micrometers to several tens of micrometers are formed so that the specific surface area of the surface at the four corner portions 68a, 68b, 68c, and 68d of the electrode leads 60 and 70 is obtained. Rapidly increasing and heat-sealed with the lead film 80, the adhesion is significantly improved to prevent the electrolyte solution from leaking inside the battery case 20.

Therefore, the secondary battery according to the present invention has a tapered edge portion of the electrode lead and sandblasted to improve adhesion to the lead film by the minute uneven surface to heat-bond between the electrode lead and the lead film and the innermost layer of the battery case. By maintaining the stability and sealing of the heat seal (heat seal) by the stable it can be prevented from infiltrating moisture from the outside and leakage of the electrolyte inside.

Description of the Related Art
10: secondary battery 20: battery case
30: electrode assembly 40, 50: electrode tab
60, 70: electrode lead 80: lead film

Claims (3)

A secondary battery in which an electrode assembly 30 having a cathode / separation membrane / cathode structure is built in the pouch type battery case 20 is connected to the electrode tabs 40 and 50 of the electrode assembly 30 and the battery case ( An electrode lead (60, 70) formed by tapering the edge portion adhered to the lead film (80) by a slanted angle at an angle of 100 ° or more;
An electrode comprising a lead film (80) configured to bond the electrode leads (60, 70) to the battery case (20) by surrounding the electrode leads (60, 70) and to form insulation at the same time. Secondary battery with improved adhesion at the edges of leads.
According to claim 1, wherein the left and right edges of the electrode leads (60, 70) is also formed so that the angle is not rounded, it is difficult to generate cracks due to the sharpness, it is possible to prevent the phenomenon that the charge concentrated on the tip portion A secondary battery having improved adhesion of the edge portion of the electrode lead.
The tapered four corner portions 68a, 68b, 68c, and 68d of the electrode leads 60 and 70 are sandblasted on the surface to improve adhesion to the lead film 80. The secondary battery with improved adhesion of the edge portion of the electrode lead, characterized in that to form a fine concave-convex surface on the surface of the electrode lead (60, 70).

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