Patent Description:
The present invention relates to a pouch-type secondary battery and a method of manufacturing the same, and more particularly to a pouch-type secondary battery and a method of manufacturing the same, capable of completely protecting a metal layer from moisture or air by forming an insulating coating layer including a conformal coating layer on the metal layer exposed to a cut surface of a battery case.

As mobile devices have been continuously developed and the demand for mobile devices has increased, secondary batteries, which are capable of being charged and discharged, have been used as energy sources for various mobile devices. In addition, secondary batteries have also attracted considerable attention as energy sources for electric vehicles and hybrid electric vehicles, which have been presented as alternatives to existing gasoline and diesel vehicles using fossil fuels.

Based on the shape of a battery case, secondary batteries are classified into a cylindrical battery having an electrode assembly mounted in a cylindrical metal can, a prismatic battery having an electrode assembly mounted in a prismatic metal can, and a pouch-shaped battery having an electrode assembly mounted in a pouch-shaped case made of an aluminum laminate sheet.

The electrode assembly, which is mounted in the battery case, is a power generating element that is configured to have a structure including a positive electrode, a negative electrode, and a separator that is interposed between the positive electrode and the negative electrode and that can be charged and discharged. The electrode assembly is classified as a jelly-roll type electrode assembly, which is configured to have a structure in which a long sheet type positive electrode and a long sheet type negative electrode, to which active materials are applied, are wound in the state in which a separator is disposed between the positive electrode and the negative electrode, or a stacked type electrode assembly, which is configured to have a structure in which a plurality of positive electrodes having a predetermined size and a plurality of negative electrodes having a predetermined size are sequentially stacked in the state in which separators are disposed respectively between the positive electrodes and the negative electrodes. The jelly-roll type electrode assembly has advantages in that it is easy to manufacture the jelly-roll type electrode assembly and in that the jelly-roll type electrode assembly has high energy density per unit weight.

As shown in <FIG>, such a secondary battery is configured to have a structure in which an electrode assembly <NUM> is mounted in a battery case <NUM> and in which positive and negative electrode tabs and are welded respectively to two lead members <NUM>, which are exposed out of the battery case <NUM>.

Meanwhile, the battery case <NUM> configured to receive the electrode assembly <NUM> has a structure in which a lower case <NUM> and an upper case <NUM> covering the lower case <NUM> are integrally formed, and a surface in which the lower case <NUM> and the upper case <NUM> contact each other is bent and folded. The lower case <NUM> and the upper case <NUM> have a laminate structure consisting of an inner coating layer, a metal layer and an outer coating layer. In the case of a general pouch-type secondary battery manufacturing method, a process of cutting the lower case <NUM> and the upper case <NUM> is involved, and in this process, the metal layer is exposed to the outside, which is a cause for significantly reducing the battery performance, such as accelerating the deterioration of the battery.

As an example of the conventional art for solving the above problem, <CIT> discloses a method of manufacturing a pouch-type secondary battery including a step of receiving an electrode assembly between an upper sheathing member and a lower sheathing member of a pouch, a step of primary sealing an outer regions of the upper sheathing member and the lower sheathing member of the pouch, a step of cutting edges of the upper sheathing member and the lower sheathing member of the sealed pouch, and a step of pressing distal ends of the upper sheathing member and the lower sheathing member of the cut pouch to form an additional sealing portion on a surface of a cutting portion of the upper sheathing member and the lower sheathing member.

According to the above-mentioned prior document, there is an advantage that it can prevent the disadvantage in which an exposed portion of a metal layer is in contact with a metal material of a pack unit by forming an additional sealing portion on the surface of the cutting portion of the sheathing member. Since a part of a material of an inner resin layer is leaked to the outside of the cut surface through the pressing to form the additional sealing portion, however, the inner resin layer should be formed thick, and thus there is a problem that the overall volume of the battery case is increased. In addition, there is a problem that a part of an exposed surface of the metal layer is not likely to form a sealing portion because the additional sealing portion is simply formed relying on the pressing.

<CIT>
<CIT>, <CIT>, <CIT> disclose a layer formed at a side surface of a sealing portion of a battery case.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method of manufacturing a pouch-type secondary battery having a simple process and a low defective rate and a pouch-type secondary battery manufactured thereby by forming a coating layer covering a metal layer on a side surface of a sealing portion configured to couple an upper case and a lower case.

In accordance with the present invention, the above and other objects can be accomplished by the provision of a pouch-type secondary battery as defined in the appended set of claims, the pouch-type secondary battery including a battery case made of a laminate sheet; and an electrode assembly received in the batter case, wherein the battery case is composed of an upper case and a lower case made of a laminate sheet including an outer coating layer, a metal layer and an inner coating layer; a sealing portion configured to couple the upper case and the lower case to each other is provided at an outer periphery of the upper case and the lower case; and a conformal coating layer configured to prevent exposure of the metal layer is formed at a side surface of the sealing portion.

Here, a resin coating layer is further formed on a predetermined area of an outer surface of the conformal coating layer, and the resin coating layer may be formed by melting a portion of the outer coating layer.

Alternatively, a resin coating layer is further formed on a predetermined region of an inner surface of the conformal coating layer, and the resin coating layer is formed by melting a portion of the outer coating layer and/or the inner coating layer.

Also, it is provided a method of manufacturing a pouch-type secondary battery as defined in the appended set of claims. The method of manufacturing of a pouch-type secondary battery according to a first embodiment of the present invention includes a first step of preparing a battery case including an upper case and a lower case by cutting a laminate sheet including an outer coating layer, a metal layer, and an inner coating layer; a second step of receiving an electrode assembly between the upper case and the lower case; a third step of closely contacting a sealing portion provided at an outer periphery of the upper case and the lower case; and a fourth step of forming a conformal coating layer on a side surface of the sealing portion so as to prevent the exposure of the metal layer.

Also, in the method of manufacturing of the pouch-type secondary battery according to the present invention, it further includes a fifth step of sealing the upper case and the lower case by heat sealing the sealing portion of the upper case and the lower case.

Also, in the fifth step, a resin coating layer is formed on a predetermined area of an outer surface of the conformal coating layer, wherein the resin coating layer is formed of a part of the outer coating layer melted during the heat sealing of the sealing portion.

Also, a method of manufacturing of a pouch-type secondary battery according to a second embodiment of the present invention as defined in the appended set of claims, the method includes a first step of preparing a battery case including an upper case and a lower case by cutting a laminate sheet comprising an outer coating layer, a metal layer, and an inner coating layer; a second step of receiving an electrode assembly between the upper case and the lower case; a third step of closely contacting a sealing portion provided at an outer periphery of the upper case and the lower case; a fourth step of sealing the upper case and the lower case by heat sealing the sealing portion of the outer periphery of the upper case and the lower case; and a fifth step of forming a conformal coating layer on a side surface of the sealing portion so as to prevent the exposure of the metal layer.

Also, in the fourth step, a resin coating layer is partially formed on a predetermined area of a side surface of the sealing portion, the resin coating layer being formed of a part of the outer coating layer and/or the inner coating layer melted during the heat sealing of the sealing portion.

In addition, a battery module according to the present invention is the battery module including the pouch-type secondary battery.

In addition, a battery pack according to the present invention is the battery pack including the battery module.

In the present application, it should be understood that the terms "comprises," "has," or "includes," etc. specify the presence of features, integers, steps, operations, components, parts, or combinations thereof 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.

In the case in which one part is said to be connected to another part in the specification, not only may the one part be directly connected to the another part, but also, the one part may be indirectly connected to the another part via a further part.

Hereinafter, a pouch-type secondary battery and a method of manufacturing the same according to the present invention will be described with reference to the accompanying drawings.

<FIG> is a flowchart illustrating a method of manufacturing a pouch-type secondary battery according to a preferred first embodiment of the present invention, and <FIG> is a process diagram illustrating an assembly process of an upper case and a lower case according to the first embodiment.

The method of manufacturing the pouch-type secondary battery according to the first embodiment of the present invention includes a first step of preparing a battery case <NUM> including an upper case <NUM> and a lower case <NUM>; a second step of receiving an electrode assembly <NUM> between the upper case <NUM> and the lower case <NUM>; a third step of closely contacting a sealing portion <NUM> provided at an outer periphery of the upper case <NUM> and the lower case <NUM>; a fourth step of forming a conformal coating layer <NUM> on a side surface of the sealing portion <NUM>; and a fifth step of sealing the upper case <NUM> and the lower case <NUM> by heat sealing the sealing portion <NUM> of the outer periphery of the upper case <NUM> and the lower case <NUM>.

First, the first step of preparing the battery case <NUM> including the upper case <NUM> and the lower case <NUM> and the second step of receiving the electrode assembly <NUM> between the upper case <NUM> and the lower case <NUM> will be described in more detail. The battery case <NUM> is a case accommodating the electrode assembly <NUM>, and forms a space part which can accommodate the electrode assembly <NUM> using a laminate sheet made of outer coating layers <NUM> and <NUM>; metal layers <NUM> and <NUM>; and inner coating layers <NUM> and <NUM>.

The inner coating layers <NUM> and <NUM> directly contact the electrode assembly <NUM>. For this reason, it is necessary for the inner coating layers to exhibit an insulation property and electrolytic resistance. In addition, for hermetically sealing the inside and the outside of the pouch-type secondary battery, it is necessary for the inner coating layers to exhibit high sealability. Thus, it is necessary for a sealing portion, formed by thermally adhering inner coating layers of the upper case and the lower case, to exhibit excellent thermal adhesive strength.

The material for the inner coating layers <NUM> and <NUM> may be selected from among a polyolefin-based resin, such as polypropylene, polyethylene, polyethylene acrylate, or polybutylene, a polyurethane resin, and a polyimide resin, which exhibit excellent chemical resistance and good sealability. However, the present invention is not limited thereto. For example, polypropylene, which exhibits excellent mechanical properties, such as tensile strength, rigidity, surface hardness, and impact resistance, as well as excellent chemical resistance, is the most preferable.

The metal layers <NUM> and <NUM>, which abut the inner coating layers <NUM> and <NUM>, correspond to a barrier layer configured to prevent the permeation of moisture or various kinds of gases from the outside into the battery. An aluminum thin film, which is lightweight and exhibits excellent formability, may be used as a preferred material for the metal layer.

The outer coating layers <NUM> and <NUM> are provided at the other surfaces of the metal layers <NUM> and <NUM>. The outer coating layers <NUM> and <NUM> may be made of a heat-resistant polymer that exhibits excellent tensile strength, moisture permeation prevention capability, and air permeation prevention capability such that the outer coating layer exhibits heat resistance and chemical resistance while protecting the electrode assembly <NUM>. In an example, the outer coating layer may be made of nylon or polyethylene terephthalate. However, the present invention is not limited thereto.

The electrode assembly <NUM> received in the battery case <NUM> may be a jelly-roll type electrode assembly, which is configured to have a structure in which a long sheet type positive electrode and a long sheet type negative electrode are wound in the state in which a separator is interposed between the positive electrode and the negative electrode, a stacked type electrode assembly including unit cells, each of which is configured to have a structure in which a rectangular positive electrode and a rectangular negative electrode are stacked in the state in which a separator is interposed between the positive electrode and the negative electrode, a stack/folded type electrode assembly, which is configured to have a structure in which the unit cells are wound in the state in which the unit cells are disposed on a long separation film, or a laminated/stacked type electrode assembly, which is configured to have a structure in which the unit cells are stacked so as to be attached to each other in the state in which a separator is interposed between the unit cells. However, the present invention is not limited thereto.

A lead member <NUM>, which generally includes a positive electrode lead and a negative electrode lead, is configured to have a structure in which a positive electrode tab (not shown) and a negative electrode tab (not shown), which are attached to the upper end of the electrode assembly <NUM>, are electrically connected to the positive electrode lead and the negative electrode lead, respectively, by welding and in which the lead member <NUM> is exposed out of the battery case <NUM>. At this time, in order to provide insulativity and sealability, a pair of insulative films (not shown), which face each other, is located in the region of the sealing portion <NUM> at which the positive electrode lead and the negative electrode lead are located, and the lead member <NUM> is disposed so as to extend between the pair of insulative films (not shown).

In the third step of closely contacting the sealing portion <NUM> provided at the outer periphery of the upper case <NUM> and the lower case <NUM>, the sealing portion <NUM> of the upper case <NUM> and the sealing portion <NUM> of the lower case <NUM> are simply brought into close contact with each other, in the state in which the electrode assembly <NUM> is accommodated. Specifically, using a pair of sealing bars <NUM> located on the top and bottom of the sealing portion <NUM> of the upper case <NUM> and the lower case <NUM>, the sealing portion <NUM> of the upper case <NUM> and the lower case <NUM> is pressed by a predetermined force to be in close contact with each other. At this time, the sealing portion <NUM> is not heated, and therefore, melting of the inner coating layers <NUM> and <NUM> and the outer coating layers <NUM> and <NUM> does not occur.

Here, the pair of sealing bars <NUM> are preferably further provided with a bent portion <NUM> bent at a predetermined angle, and a wing portion <NUM> extending from the bent portion <NUM>.

More specifically, one of the sealing bars <NUM> in contact with the upper surface of the outer coating layer <NUM> of the upper case <NUM> includes the bent portion <NUM>, which is bent downward after extending a predetermined length in the direction of a cut surface of the upper case <NUM>, and the wing portion <NUM> extending upward while being inclined at a predetermined angle from the bent portion <NUM>.

Also, the other sealing bar <NUM> in contact with the lower surface of the outer coating layer <NUM> of the lower case <NUM> includes the bent portion <NUM>, which is bent upward after extending a predetermined length in the direction of a cut surface of the lower case <NUM>, and the wing portion <NUM> extending downward while being inclined at a predetermined angle from the bent portion <NUM>.

When forming the conformal coating layer <NUM> performed in the fourth step, the wing portion <NUM> is provided to protect the sealing bar <NUM> from the conformal coating resin to be sprayed, and to allow the conformal coating layer <NUM> to be seated intensively at a desired position. When heating the sealing portion <NUM> performed in the fifth step, the bent portion <NUM> is provided to induce a part of the resin of the molten outer coating layers <NUM> and <NUM> to move to a desired position.

The fourth step is to form the conformal coating layer <NUM> near the sealing portion <NUM>, more specifically, on a side surface of the sealing portion <NUM>, which is a cut surface of the laminate sheet.

The upper case <NUM> and the lower case <NUM> constituting the battery case <NUM> are obtained by cutting and forming the laminate sheet including the outer coating layers <NUM> and <NUM>; the metal layers <NUM> and <NUM>; and the inner coating layers <NUM> and <NUM>. Therefore, even if the sealing portion <NUM> is heat-sealed, some or all of the metal layers <NUM> and <NUM> are generally exposed to the outside, and thus are in an electrically vulnerable state.

In the fourth step of the present invention, the conformal coating layer <NUM> is formed so that cut surfaces of the metal layers <NUM> and <NUM> are not exposed to the outside.

Here, the conformal coating layer <NUM> may be formed on the outer coating layers <NUM> and <NUM> and/or the inner coating layers <NUM> and <NUM> as well as the metal layers <NUM> and <NUM>.

Meanwhile, conformal coating is a process of forming a protective film with a predetermined resin on the surface of a PCB assembly generally completed by mounting electronic components on a printed circuit board (PCB). In other words, when the PCB assembly is prepared, the protective film is formed by coating the surface of the PCB assembly with a resin for conformal coating through various coating methods. The protective film may be formed through various methods such as a spray coating method for discharging a resin for conformal coating, a flow coating method, a dip coating method for immersing a part of the PCB assembly in a liquid resin solution for conformal coating, or a chemical vapor deposition method.

Among the above various methods, a spray coating method is preferred in the present invention because the metal layers <NUM> and <NUM> exposed to the outside, or the outer coating layers <NUM> and <NUM> and/or the inner coating layers <NUM> and <NUM> adjacent to the metal layers <NUM> and <NUM> may be selectively coated.

The resin for conformal coating is not particularly limited as long as it can form a film on the metal layers <NUM> and <NUM>, and may be subjected to a cooling process for a predetermined time for curing after spray coating.

Since the conformal coating layer on the side surface of the sealing portion <NUM> formed through the above process perfectly coats the metal layers <NUM> and <NUM>, causes of deteriorating the battery performance such as corrosion and insulation resistance caused by moisture or air coming into contact with the metal layers can be fundamentally blocked.

Subsequently, the fifth step is performed by heat sealing the sealing portion <NUM> of the outer periphery of the upper case <NUM> and the lower case <NUM> to seal the upper case <NUM> and the lower case <NUM>.

In the fifth step, in order to maintain the sealed state of the pouch-type secondary battery, the battery case <NUM> is sealed by heating the sealing portions <NUM> provided along the periphery of the upper case <NUM> and the lower case <NUM> so that the inner coating layers <NUM> and <NUM> are bonded to each other.

At this time, a part of the resin of the outer coating layers <NUM> and <NUM> is also melted together to form a resin coating layer <NUM> on a predetermined area of the outer surface of the conformal coating layer <NUM>. Since the resin coating layer <NUM> extends to the conformal coating layer <NUM> in the state in which it is connected to the outer coating layers <NUM> and <NUM>, the resin coating layer <NUM> may prevent the conformal coating layer <NUM> from being exfoliated, and may more reliably protect the metal layers <NUM> and <NUM> from moisture or air.

Moreover, since it is not necessary to form a film on all surfaces of the metal layers <NUM> and <NUM>, in order to manufacture the pouch-type secondary battery having the conformal coating layer, the thickness of the outer coating layers <NUM> and <NUM> may be the same as that of the conventional art, and it is possible to apply a conventional heat sealing temperature and time.

<FIG> is a flowchart illustrating a method of manufacturing a pouch-type secondary battery according to a preferred second embodiment of the present invention, and <FIG> is a process diagram illustrating an assembly process of an upper case and a lower case according to the second embodiment.

The method of manufacturing the pouch-type secondary battery according to the second embodiment of the present invention includes a first step of preparing a battery case <NUM> including an upper case <NUM> and a lower case <NUM>; a second step of receiving an electrode assembly <NUM> between the upper case <NUM> and the lower case <NUM>; a third step of closely contacting a sealing portion <NUM> provided at an outer periphery of the upper case <NUM> and the lower case <NUM>; a fourth step of sealing the upper case <NUM> and the lower case <NUM> by heat sealing the sealing portion <NUM> of the outer periphery of the upper case <NUM> and the lower case <NUM>; and a fifth step of forming a conformal coating layer <NUM> on a side surface of the sealing portion <NUM>.

In the method of manufacturing the pouch-type secondary battery according to the second embodiment of the present invention, the configuration of the first step to the third step is identical to the first step to the third step of the first embodiment described above, and therefore a detailed description thereof will be omitted, and the fourth and fifth steps different from the first embodiment will be described.

In the fourth step of sealing the upper case <NUM> and the lower case <NUM> by heat sealing the sealing portion <NUM> of the outer periphery of the upper case <NUM> and the lower case <NUM>, in order to maintain the sealed state of the pouch-type secondary battery, the battery case <NUM> is sealed by heating the sealing portions <NUM> provided along the periphery of the upper case <NUM> and the lower case <NUM> so that the inner coating layers <NUM> and <NUM> are bonded to each other.

At this time, a part of the molten resin of the outer coating layers <NUM> and <NUM> and/or the inner coating layers <NUM> and <NUM> flows to a side surface of the sealing portion <NUM> to form a resin coating layer <NUM> on some exposed part of the metal layers <NUM> and <NUM>.

The fifth step is a step of forming a conformal coating layer <NUM> on the side surface of the sealing portion <NUM> so that the cut surfaces of the metal layers <NUM> and <NUM> are not exposed to the outside.

When the fourth step is performed, even if the resin of the outer coating layers <NUM> and <NUM> and/or the inner coating layers <NUM> and <NUM> does not cover all the exposed surfaces of the metal layers <NUM> and <NUM>, the metal layers <NUM> and <NUM> can be protected from moisture or air since a film is formed on all the metal layers <NUM> and <NUM> by the conformal coating layer <NUM>.

The conformal coating layer <NUM> has been described in detail in the first embodiment, and therefore a description thereof will be omitted.

<FIG> is a perspective view showing a pouch-type secondary battery manufactured according to the present invention. Specifically, the pouch-type secondary battery manufactured according to the first or second embodiment of the present invention includes an electrode assembly <NUM> received in a battery case <NUM> composed of an upper case <NUM> and a lower case <NUM> made of a laminate sheet including outer coating layers <NUM> and <NUM>, metal layers <NUM> and <NUM>, and inner coating layers <NUM> and <NUM>.

In addition, a coating layer <NUM> for preventing exposure of the metal layer is additionally formed on a side surface of a sealing portion <NUM> for coupling the upper case <NUM> and the lower case <NUM>.

Specifically, as described in <FIG>, the pouch-type secondary battery manufactured according to the first embodiment is provided with the coating layer <NUM> formed in a shape in which a resin coating layer, formed by melting a part of the outer coating layer <NUM> and <NUM>, is additionally formed on a predetermined area of the outer surface of a conformal coating layer.

On the other hand, as described in <FIG>, the pouch-type secondary battery manufactured according to the second embodiment is provided with the coating layer <NUM> formed in a shape in which a resin coating layer <NUM>, formed by melting a part of the outer coating layers <NUM> and <NUM> and/or the inner coating layers <NUM> and <NUM>, is additionally formed on a predetermined area of the inner surface of the conformal coating layer <NUM>.

Although the specific details of the present invention have been described in detail, those skilled in the art will appreciate that the detailed description thereof discloses only preferred embodiments of the present invention and thus does not limit the scope of the present invention. Accordingly, those skilled in the art will appreciate that various changes and modifications are possible, without departing from the category and the technical idea of the present invention, and it will be obvious that such changes and modifications fall within the scope of the appended claims.

Claim 1:
A pouch-type secondary battery, comprising:
a battery case (<NUM>) made of a laminate sheet; and
an electrode assembly (<NUM>) received in the battery case (<NUM>), wherein
the battery case is composed of an upper case (<NUM>) and a lower case (<NUM>) made of a laminate sheet comprising an outer coating layer (<NUM>, <NUM>), a metal layer (<NUM>, <NUM>) and an inner coating layer (<NUM>, <NUM>),
a sealing portion (<NUM>) configured to couple the upper case (<NUM>) and the lower case (<NUM>) to each other is provided at an outer periphery of the upper case (<NUM>) and the lower case (<NUM>),
a conformal coating layer (<NUM>) configured to prevent exposure of the metal layer (<NUM>, <NUM>) is formed at a side surface of the sealing portion (<NUM>), and
wherein a resin coating layer (<NUM>) is further formed on a predetermined area of an outer surface of the conformal coating layer (<NUM>), the resin coating layer (<NUM>) being formed by melting a portion of the outer coating layer (<NUM>, <NUM>), or
a resin coating layer (<NUM>) is further formed on a predetermined area of an inner surface of the conformal coating layer (<NUM>), the resin coating layer (<NUM>) being formed by melting a portion of the outer coating layer (<NUM>, <NUM>) and/or the inner coating layer (<NUM>, <NUM>).