Patent Description:
The present disclosure relates to a pouch case and a method of manufacturing a pouch type secondary battery including the same.

With the increase of the technological development and demand for a mobile device, demand for a battery as an energy source rapidly increases, and accordingly, many researches of the battery capable of meeting a variety of needs are emerging.

A secondary battery has attracted considerable attention as an energy source for power-driven devices, such as an electric bicycle, an electric vehicle, and a hybrid electric vehicle, as well as an energy source for mobile devices, such as a mobile phone, a digital camera, and a laptop computer.

A small-sized battery pack, in which a battery cell is mounted, is used for small-sized devices, such as a mobile phone and a digital camera, whereas a middle or large-sized battery pack, in which a battery pack including two or more battery cells connected to each other in parallel and/or in series is mounted, is used for middle or large-sized devices, such as a laptop computer and an electric vehicle.

In view of a battery shape, a prismatic type secondary battery and a pouch type secondary battery that can be applied to products such as a mobile phone with a thin thickness shows high demand. In the case of the prismatic type lithium secondary battery, it is advantageous in protecting an electrode assembly from external impact and the injection process is easy, but the shape is fixed, which make it difficult to reduce the volume. On the other hand, the pouch type lithium secondary battery has advantages in that it is suitable for manufacturing a thin cell due to no restriction on its shape and size, it is easy to assemble the pouch type lithium secondary battery through thermal fusing, and it has high stability due to easy vent of gas or liquid under the condition of abnormal behaviors. However, since the pouch type secondary battery uses a thin soft laminated sheet as a case thereof unlike the prismatic type secondary battery, its physical and mechanical strength are weak, especially its sealing reliability is low, and so its safety against external impact and the like may be low.

The present disclosure has been made to solve the above problems, and it is therefore an object to provide a pouch case capable of improving a bonding force of a sealing part so as to increase sealing reliability, and a method of manufacturing a pouch type secondary battery including the same.

However, the problem to be solved by the embodiments of the present disclosure is not limited to the above-described problems, and can be variously expanded within the scope of the technical idea included in the present disclosure.

A pouch case according to an exemplary embodiment of the present disclosure as defined in the appended set of claims, the pouch case includes an upper case and a lower case, wherein edge parts of the upper case and the lower case each includes a substrate layer, a metal layer and a sealing layer that are sequentially stacked, and wherein at least one sealing layer of the upper case and the lower case includes a plurality of grooves that are recessed from one surface of the sealing layer.

The depth of the groove is <NUM>% to <NUM>% of the thickness of the sealing layer.

The width of the groove may be <NUM> to <NUM>.

The grooves may be formed in a lattice shape.

The interval of the lattice shape may be <NUM> to <NUM>.

The grooves may be formed in a stripe shape.

The grooves may be formed in an irregular concave-convex shape.

The sealing layer may include a thermoplastic resin.

A method of manufacturing a pouch type secondary battery according to another exemplary embodiment of the present disclosure is defined in the appended set of claims. The method includes the steps of: accommodating an electrode assembly in a space between an upper case and a lower case, and thermally fusing edge parts of the upper case and the lower case to each other, wherein edge parts of the upper case and the lower case each includes a substrate layer, a metal layer and a sealing layer that are sequentially stacked, and wherein before the step of thermally fusing, the method further includes forming a plurality of grooves on one surface of at least one sealing layer of the upper case and the lower case.

The step of forming the plurality of grooves may include applying pressure to the sealing layer by a first pressing part having a pressing surface on which a protruding shape is formed.

The pressure applied by the first pressing part may be <NUM> MPa to <NUM> MPa.

The step of thermally fusing may include applying heat while applying pressure by the second pressing part having a flat pressing surface.

According to the embodiments, it is possible to manufacture a pouch type secondary battery having improved sealing adhesion without significantly changing the manufacturing process and without affecting the appearance of the battery, by adding a plurality of grooves onto the sealing layer of the pouch case.

Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement them. The present disclosure may be modified in various different ways, and is not limited to the embodiments set forth herein.

Parts that are irrelevant to the description will be omitted to clearly describe the present disclosure, and like reference numerals designate like elements throughout the specification.

In addition, it will be understood that when an element such as a layer, film, region, or plate is referred to as being "on" or "above" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, it means that other intervening elements are not present. Further, the word "on" or "above" means disposed on or below a reference portion, and does not necessarily mean being disposed on the upper side of the reference portion toward the opposite direction of gravity.

Further, throughout the specification, when a part is referred to as "including" a certain component, it means that it can further include other components, without excluding the other components, unless otherwise stated.

Further, throughout the specification, when referred to as "on a plane", it means when a target portion is viewed from the top, and when referred to as "on a cross-section" means when a target portion is viewed from the side of a cross section cut vertically.

<FIG> is an exploded perspective view illustrating a pouch case and a secondary battery including the same according to an exemplary embodiment of the present disclosure.

As shown in <FIG>, a pouch type secondary battery has a positive electrode current collector, a separator, and a negative electrode current collector as a basic structure, and includes an electrode assembly <NUM> provided with a positive electrode tab extending from the positive electrode current collector and a negative electrode tab extending from the negative electrode current collector, and a pouch case <NUM> for accommodating the electrode assembly <NUM>.

The pouch case <NUM> includes an upper case <NUM> and a lower case <NUM>. In <FIG>, the upper case <NUM> and the lower case <NUM> are illustrated as being separated and formed from each other, but the upper case <NUM> and the lower case <NUM> may be connected and integrally formed. The shape of the pouch case <NUM> is not limited to that illustrated in <FIG>, and any shape may be used as long as it is a shape that can accommodate and seal the electrode assembly <NUM>. The upper case <NUM> and the lower case <NUM> in <FIG> each includes an accommodating part having a recessed concave shape. The electrode assembly <NUM> and the electrolyte may be accommodated in the accommodating part.

The electrode assembly <NUM> may be configured in a form in which a positive electrode plate and a negative electrode plate are disposed with a separator being interposed between them. At this time, the electrode assembly <NUM> may have a structure in which one positive electrode plate and one negative electrode plate are wound with a separator being interposed between them, or a structure in which a plurality of positive electrode plates and a plurality of negative electrode plates may be stacked with a separator being interposed between them. The positive electrode plate and the negative electrode plate may be respectively formed as a structure in which an active material slurry is coated onto the electrode current collector. The slurry may typically be formed by stirring an active material, a conductive material, a binder, a plasticizer, and the like in the presence of a solvent.

The electrode assembly <NUM> may have a noncoated part where the slurry is not coated onto the electrode plate, and electrode tabs corresponding to the respective electrode plates may be formed in the noncoated part. At this time, for electrical connection with external terminals or devices, a part of a positive electrode lead <NUM> extending from the positive electrode tab and a negative electrode lead <NUM> extending from the negative electrode tab may have a form exposed to the outside. In this regard, an adhesive film may be further used for attaching or bonding to the pouch case <NUM> of the electrode lead in accordance with the exemplary embodiment.

<FIG> is an enlarged cross-sectional view of parts A and B in <FIG>.

Referring to <FIG> and <FIG>, the upper case <NUM> and the lower case <NUM> constituting the pouch case according to an exemplary embodiment of the present disclosure include sealing parts 110a and 120a formed at edge parts of the pouch case <NUM> surrounding the accommodating part in which the electrode assembly <NUM> of <FIG> is accommodated. The sealing parts 110a and 120a are formed along the edge parts of the pouch case <NUM>, and all or part of the sealing parts 110a and 120a may be a bonding area to which the upper case <NUM> and the lower case <NUM> are bonded. The upper case <NUM> and the lower case <NUM> may be thermally fused to seal a pouch case <NUM>.

Looking at the cross-sectional structure of the pouch case <NUM> located in the bonding area, each of the upper case <NUM> and the lower case <NUM> includes substrate layers <NUM> and <NUM>, metal layers <NUM> and <NUM>, and sealing layers <NUM> and <NUM>. The stacking direction of the first substrate layer <NUM>, the first metal layer <NUM>, and the first sealing layer <NUM> included in the upper case <NUM> and the stacking direction of the second substrate layer <NUM>, the second metal layer <NUM> and the second sealing layer <NUM> included in the lower case <NUM> are opposite to each other. Specifically, as shown in <FIG>, the upper case <NUM> includes a first substrate layer <NUM>, a first metal layer <NUM>, and a first sealing layer <NUM> that are sequentially located toward the inside from the outside of the upper case <NUM>. The lower case <NUM> includes a second substrate layer <NUM>, a second metal layer <NUM>, and a second sealing layer <NUM> that are sequentially located toward the inside from the outside of the lower case <NUM>. At this time, the first sealing layer <NUM> and the second sealing layer <NUM> are in contact with each other and thermally fused to form a sealed structure.

An adhesive layer (not shown) may also be located between the first substrate layer <NUM> and the first metal layer <NUM>, between the first metal layer <NUM> and the first sealing layer <NUM>, between the second substrate layer <NUM> and the second metal layer <NUM> and between the second metal layer <NUM> and the second sealing layer <NUM>, respectively.

The first substrate layer <NUM> and the second substrate layer <NUM> may be made of an insulating material such as polyethylene terephthalate (PET) resin or nylon resin in order to secure insulation and formability between the secondary battery and the outside.

The first metal layer <NUM> and the second metal layer <NUM> may include any one selected from the group consisting of copper, aluminum, nickel, iron, carbon, chromium, manganese, and alloys thereof.

The first sealing layer <NUM> and the second sealing layer <NUM> according to the present embodiment may include a thermoplastic resin. The thermoplastic resin may include polypropylene (PP).

The first sealing layer <NUM> and the second sealing layer <NUM> include a plurality of grooves <NUM> and <NUM> that are recessed from one surface of the first sealing layer <NUM> and the second sealing layer <NUM>. That is, a plurality of grooves <NUM> and <NUM> respectively recessed in the direction toward the first metal layer <NUM> and the second metal layer <NUM> are formed from one surface of the first sealing layer <NUM> and the second sealing layer <NUM> which are surfaces where the upper case <NUM> and the lower case <NUM> face each other.

The shape of the plurality of grooves <NUM> and <NUM> is not particularly limited. For example, it may be formed in a shape in which the grooves <NUM> and <NUM> are arranged in a lattice shape, a stripe shape, or an irregular shape. Among them, it may be formed in a lattice shape from the viewpoint of ease of processing, etc., but it is not particularly limited. At this time, intersecting lines of the lattice shape may be formed at an angle of <NUM> to <NUM> degrees, preferably <NUM> to <NUM> degrees, more preferably <NUM> degrees with respect to the outer periphery of the pouch case <NUM>, and this is also not particularly limited. In addition, the interval between the lattice-shaped intersecting lines can be appropriately adjusted according to the depth and thickness of the grooves <NUM> and <NUM> to be described later, and preferably, it may be <NUM> to <NUM>.

The plurality of grooves <NUM> and <NUM> has a depth d of <NUM>% to <NUM>% with respect to the thickness of the sealing layers <NUM> and <NUM>. Preferably, the depth d of the grooves <NUM> and <NUM> may be <NUM>% to <NUM>% and more preferably <NUM>% to <NUM>% of the thickness of the sealing layers <NUM> and <NUM>.

If the depth d is less than <NUM>%, the sealing adhesion is not sufficiently improved, and if the depth is more than <NUM>%, not only does it cause damage to the metal layers <NUM> and <NUM>, but also the sealing thickness becomes thin and rather, the adhesive force of the sealing layers <NUM> and <NUM> can be reduced, which is not preferable.

In addition, the plurality of grooves <NUM> and <NUM> may have a width w of about <NUM> to about <NUM>. If the width w is less than <NUM>, the sealing adhesion is not sufficiently improved and the workability is not good. If the width is <NUM> or more, it may cause damage to the metal layers <NUM> and <NUM> and it is likely to damage the sealing layers <NUM> and <NUM>, which is not preferable.

By forming the plurality of grooves <NUM> and <NUM> in the sealing layers <NUM> and <NUM> as described above, when the upper case <NUM> and the lower case <NUM> are thermally fused, the contact surfaces which are in contact with each other are increased, and thus the adhesive force is enhanced, thereby increasing the sealing reliability. In addition, grooves are not formed in all layers forming the upper case <NUM> and the lower case <NUM>, but the grooves <NUM> and <NUM> are formed only in the sealing layers <NUM> and <NUM> to be thermally fused, whereby flat sealing parts 110a and 120a can be obtained without bending in appearance, and thus, it may not affect subsequent folding processes, etc. That is, due to bending or wrinkles remaining in the sealing parts 110a and 120a, damage to the pouch or the like may occur during folding, or the problem of excessive sealing may occur. As described above, the grooves for improving the sealing adhesion are formed only in the sealing layers <NUM> and <NUM> and do not affect the appearance, thereby preventing the occurrence of these problems.

Hereinafter, a method of manufacturing a pouch type secondary battery according to an exemplary embodiment of the present disclosure will be described with reference to <FIG> and <FIG>.

<FIG> is a flowchart illustrating a method of manufacturing a pouch type secondary battery according to an exemplary embodiment of the present disclosure. <FIG> and <FIG> are diagrams illustrating a pressing process by the pressing part.

First, the lower case <NUM> of the pouch case <NUM> and the electrode assembly <NUM> are disposed on a pressing plate <NUM> (S10). At this time, a part of a positive electrode lead <NUM> and a negative electrode lead <NUM> of the electrode assembly <NUM> is disposed so as to be exposed to the outside of the lower case <NUM>.

Next, as illustrated in <FIG>, the sealing part 120a of the lower case <NUM> is pressed using a first pressing part <NUM> to form a plurality of grooves <NUM> (S20). That is, pressure is applied to the second sealing layer <NUM> located on the upper surface of the sealing part 120a by using the first pressing part having a pressing surface where a shape protruding from the surface is formed (an enlarged part in <FIG>), so that the grooves <NUM> recessed from the upper surface can be formed. At this time, the pressure applied by the first pressing part <NUM> may be <NUM> MPa to <NUM> MPa, preferably <NUM> MPa. When the pressure applied by the first pressing part <NUM> is less than <NUM> MPa, grooves having sufficient depth cannot be formed on the surface of the second sealing layer <NUM>. When the pressure is <NUM> MPa or more, the second metal layer <NUM> located below the second sealing layer <NUM> may be damaged, which is not preferable.

In addition, although not separately illustrated in the present specification, the grooves <NUM> can be formed even in the upper case <NUM> through the same process. That is, grooves may be formed on at least one side of the upper case <NUM> and the lower case <NUM>. Moreover, the grooves <NUM> and <NUM> of the upper case <NUM> and the lower case <NUM> may be formed only on a pair of sides where the electrode leads <NUM> and <NUM> are not formed, as shown in <FIG>, and the grooves may also be formed on all sides of the pouch case <NUM> including the part where the electrode leads <NUM> and <NUM> are formed as shown in <FIG>, without being particularly limited.

Next, as shown in <FIG>, the upper case <NUM> is disposed so as to cover the lower case <NUM> and the electrode assembly <NUM>, and heat is applied while applying pressure by the second pressing part <NUM> having a flat pressing surface to thereby thermally fuse the first and second sealing layers <NUM> and <NUM> (S30). That is, by applying heat and pressure, the first and second sealing layers <NUM> and <NUM> including the thermoplastic resin are thermally fused to form one integrated sealing layer (not shown). Thereby, the sealed structure of the pouch case is formed to fabricate a pouch type secondary battery.

As described above, before the thermal fusing process of the sealing layers <NUM> and <NUM>, the grooves <NUM> and <NUM> are formed on the upper surfaces of the sealing layers <NUM> and <NUM> by adding a pressing process by the first pressing part <NUM>, and then the thermal fusing process is performed by the second pressing part <NUM>, whereby during the thermal fusing process, contact area between the first and second sealing layers <NUM> and <NUM> is increased, so that a sealed structure having enhanced adhesion can be obtained. Further, even if the grooves <NUM> and <NUM> are formed in this way, since only the pressing step by the first pressing part <NUM> is simply added, existing equipment can be used to improve the sealing performance. Further, the grooves <NUM> and <NUM> are formed only in the sealing layers <NUM> and <NUM> by the first pressing part <NUM>, and the sealing adhesion can be enhanced without damaging the metal layers <NUM> and <NUM> and the substrate layers <NUM> and <NUM> of the pouch case <NUM>.

On the other hand, in the following, the pouch case according to the present disclosure will be described in detail by way of specific examples and comparative examples.

For each of the first and second sealing layers containing polypropylene (PP), samples each having thicknesses set to <NUM>, <NUM> and <NUM> were prepared.

A pressure of <NUM> MPa to <NUM> MPa was applied to each of the first and second sealing layers by the first pressing part of the present disclosure to form a plurality of grooves having a depth of <NUM>% relative to the thickness of the first and second sealing layers.

Next, heat and pressure were applied by using the second pressing part of the present disclosure, and the first and second sealing layers were thermally fused at a sealing temperature of <NUM> to manufacture a pouch case.

A pouch case was manufactured in the same manner as in Example <NUM>, except that a plurality of grooves having a depth of <NUM>% relative to the thickness of the first and second sealing layers were formed in each of the first and second sealing layers having thicknesses of <NUM>, <NUM>, and <NUM>.

A pouch case was manufactured in the same manner as in Example <NUM>, except that no grooves were formed in each of the first and second sealing layers having thicknesses of <NUM>, <NUM>, and <NUM>.

For the pouch cases of Examples <NUM> to <NUM> and Comparative Examples <NUM> and <NUM>, an adhesion test was performed for each sample. Specifically, each sample was cut to a width of <NUM> using a UTM (Universal Testing Machine) equipment, and then both ends were pulled to measure the adhesive force (kg/mm). Ten samples were measured for each thickness, and the average, minimum and maximum values of the measured adhesive forces (kg/mm) are shown in Table <NUM> below.

Next, based on the average value of Table <NUM>, the degree of increase in the adhesion force of Examples <NUM>, <NUM>, <NUM> and Comparative Example <NUM> compared to Comparative Example <NUM> in which no grooves were formed is shown in Table <NUM> below.

Referring to Table <NUM> and Table <NUM>, when forming grooves having a depth of <NUM>% to <NUM>% relative to the thickness of the sealing layer as in Examples <NUM> to <NUM>, it can be confirmed that contact surface between the sealing layers was increased compared to Comparative Example <NUM> in which the grooves were not formed, thereby enhancing the adhesive force. In particular, in Examples <NUM> to <NUM>, the adhesive force of the sealing layer was increased by <NUM>%, <NUM>% and <NUM>%, respectively, compared to Comparative Example <NUM>.

Claim 1:
A pouch case (<NUM>) comprising: an upper case (<NUM>) and a lower case (<NUM>),
wherein edge parts of the upper case (<NUM>) and the lower case (<NUM>) each includes a substrate layer (<NUM>, <NUM>), a metal layer (<NUM>, <NUM>) and a sealing layer (<NUM>, <NUM>) that are sequentially stacked,
wherein at least one sealing layer (<NUM>, <NUM>) of the upper case (<NUM>) and the lower case (<NUM>) includes a plurality of grooves (<NUM>, <NUM>) that are recessed from one surface of the sealing layer (<NUM>, <NUM>), and
wherein a depth (d) of the groove (<NUM>, <NUM>) is <NUM>% to <NUM>% of the thickness of the sealing layer (<NUM>, <NUM>).