Patent Description:
More particularly, the present invention relates to a battery cell including a sealed portion having an embossed pattern formed thereon, wherein the embossed pattern is configured to prevent easy venting of a sealed portion of a pouch-shaped battery cell.

A lithium secondary battery, which is capable of being charged and discharged, has been widely used as an energy source for wireless mobile devices or wearable devices, which are worn on bodies, and has also been used as an energy source for electric vehicles and hybrid electric vehicles presented as alternatives to existing gasoline and diesel vehicles, which cause air pollution.

Depending on the material and shape of a battery case, the lithium secondary battery may be classified as a cylindrical battery cell having an electrode assembly mounted in a metal can, a prismatic battery cell having an electrode assembly mounted in a metal can, or a pouch-shaped battery cell having an electrode assembly mounted in a battery case made of a laminate sheet. The pouch-shaped battery cell has advantages of easy deformation and high energy density.

In order to seal the pouch-shaped battery cell, a method of pressing an outer periphery of the battery case using a high-temperature sealing block to form a sealed portion is used. If such a sealing method is used, however, venting of the pouch-shaped battery cell easily occurs when internal pressure of the pouch-shaped battery cell is increased.

Accordingly, methods of improving sealability of the pouch-shaped battery cell have been devised.

Patent Document <NUM> discloses a power storage device configured such that, in a sealed container formed of a power storage device sheathing member including a metal foil layer, an anti-corrosion treatment layer, and a sealant layer, which are sequentially stacked, an edge portion at which the sealant layers contact each other is sealed by thermal sealing, and a thin concave portion is formed at the edge portion.

In Patent Document <NUM>, the thin portion is formed at the sealed portion formed by thermal sealing, whereby the edge portion is easily bent.

Patent Document <NUM> discloses a film coated battery including a sheathing film configured such that at least a thermally fusible resin layer and a metal thin film layer are stacked, a battery element is surrounded in the state in which the thermally fusible resin layer faces inside, and a peripheral joining portion is thermally fused to seal the battery element, wherein at least one bent portion is formed at the joining portion, and the thickness of the bent portion is less than the thickness of the joining portion around the bent portion.

In Patent Document <NUM>, the bent portion having a relatively small thickness is formed at the joining portion of the sheathing film, whereby formation of cracks at the bent portion due to difference in extension of the film inside and outside the joining portion is prevented.

Patent Document <NUM> discloses a sealing device for performing preliminary sealing, the preliminary sealing and main sealing being sequentially performed in order to seal a pouch-shaped battery case, wherein the sealing device includes a press configured to heat and press one surface and the other surface of an outer periphery of a sheet member for battery cases in order to form a preliminary sealed portion and a pair of sealing blocks, each including a fixing portion configured to fix the sheet member, a sealing protrusion is formed on the press so as to protrude outwards, and an outer end of the sealing protrusion is round when viewed in vertical section.

In Patent Document <NUM>, the preliminary sealing is performed before the main sealing, whereby formation of wrinkles on an outer surface of a battery cell is reduced.

However, the above patent documents do not suggest technology capable of easily providing a structure capable of increasing sealing force of a pouch-shaped battery cell, and therefore there is a need to develop such technology.

In addition, the document <CIT> provides an example of rechargeable battery to secure sealing property at a sealing interface of a laminate sheet forming a case.

The document <CIT> provides an example of a secondary battery suitable for a wearable device or a portable information terminal.

The document <CIT> provides an example of a laminated battery (having a sealing part guiding the electrode terminal outside formed in a concavo-convex shape.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a battery cell including a sealed portion having an embossed pattern formed thereon such that a structure in which sealing force of a sealed portion of a pouch-shaped battery cell is increased is applicable using a simple method.

A battery cell according to the present invention to accomplish the above object is provided in the appended claims.

As is apparent from the above description, a battery cell is configured such that an embossed pattern is formed on the entirety of a sealed portion, whereby the total surface area of the sealed portion is increased. Consequently, contact area between an upper case and a lower case may be increased, and therefore sealing force of the battery cell may be increased.

Even when a pouch-shaped battery cell is deformed, therefore, it is possible to prevent opening of the sealed portion, and even when internal pressure of the battery cell is increased, it is possible to inhibit explosion of the battery cell.

In addition, it is possible to form the embossed pattern on the sealed portion during a conventional battery cell manufacturing process, and therefore expansion of production facilities is unnecessary.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<FIG> is a perspective view of a battery cell according to a first embodiment.

The battery cell <NUM> is a pouch-shaped battery cell including a pouch-shaped battery case <NUM> made of a laminate sheet. The pouch-shaped battery case <NUM> includes an upper case <NUM> having an electrode assembly receiving portion <NUM> configured to receive an electrode assembly formed therein and a lower case <NUM> located under the upper case <NUM>.

The battery case may be made of a laminate sheet configured such that an outer resin layer, an air and moisture blocking metal layer, and a thermally fusible inner resin layer are stacked.

It is required for the outer resin layer to exhibit excellent tolerance to an external environment, and therefore more than predetermined tensile strength and weather resistance are necessary. For example, the outer resin layer may include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or oriented nylon.

The metal layer may be made of aluminum (Al) or an aluminum alloy in order to exhibit a function of improving strength of the battery case in addition to a function of preventing introduction of foreign matter, such as gas and moisture, or leakage of an electrolytic solution.

A polymer resin that exhibits thermal fusibility, has low hygroscopicity to the electrolytic solution, and is not expanded or eroded by the electrolytic solution may be used as the inner resin layer. For example, the inner resin layer may be made of a cast polypropylene (CPP) film.

The upper case <NUM> and the lower case <NUM> contact each other at outer peripheries thereof that surround the electrode assembly receiving portion. When the outer peripheries are heated and pressed, the inner resin layer of the upper case and the inner resin layer of the lower case are melted and coupled to each other to form a sealed portion <NUM>.

In the battery cell <NUM>, the upper case <NUM> and the lower case <NUM> are connected to each other, and the sealed portion <NUM> is formed at three direction outer peripheries thereof excluding a bent portion.

That is, the sealed portion formed at the three-way outer peripheries includes overall width direction (W) sealed portions located at opposite ends of the battery cell and an overall length direction (H) sealed portion, and an embossed pattern <NUM> is formed on all of the sealed portions.

The embossed pattern <NUM> may be formed on all of the sealed portions so as to have regular sizes. In an embodiment not according to the invention, it is disposed at regular intervals such that all of the sealed portions have the same sealing force.

According to the invention, since internal pressure is most greatly increased in an overall length direction middle part of the overall length direction (H) sealed portion, the embossed pattern is formed on the overall length direction middle part at smaller intervals.

Alternatively, electrode leads <NUM> extend outwards from the battery case at the overall width direction (W) sealed portions, and sealing force at parts from which the electrode leads <NUM> protrude is further reduced. In order to prevent reduction in sealing force at the parts from which the electrode leads <NUM> protrude, therefore, the embossed pattern formed on the sealed portions in directions in which the electrode leads <NUM> protrude may be formed at smaller intervals than the embossed pattern formed on the sealed portion in a direction in which the electrode leads <NUM> do not protrude. This construction may also be equally applied to a unidirectional battery cell configured such that electrode leads protrude from one direction sealed portion.

The embossed pattern formed on the battery cell <NUM> generally has a cylindrical shape and a circular shape when viewed in plan. However, the shape of the embossed pattern is not particularly restricted as long as it is possible to increase the adhesion area between the upper case and the lower case. For example, the vertical section of the embossed pattern may be polygonal, semicircular, or semielliptical.

In the present invention, the embossed pattern is formed in order to increase the adhesion area of the battery case on the sealed portion. The embossed pattern may be formed such that relief parts when viewed from above the sealed portion are recess parts when viewed from under the sealed portion and such that recess parts when viewed from above the sealed portion are relief parts when viewed from under the sealed portion.

<FIG> is a perspective view of a battery cell according to a second embodiment.

Referring to <FIG>, an upper case <NUM> and a lower case <NUM> constituting a pouch-shaped battery case <NUM> of the battery cell <NUM> are shown as being spaced apart from each other for convenience of description; however, the upper case <NUM> and the lower case <NUM> are brought into tight contact with each other by thermal fusion.

The battery cell <NUM> is configured to have a structure in which an electrode assembly receiving portion <NUM> is formed in each of the upper case <NUM> and the lower case <NUM> in order to receive a bidirectional electrode assembly having electrode leads <NUM> protruding in opposite directions, which may be more suitable to manufacture a high-capacity battery cell.

The battery cell <NUM> is different in shape of an embossed pattern from the battery cell <NUM>. Specifically, the embossed pattern <NUM> generally has a quadrangular prism shape and a quadrangular shape when viewed in plan. In addition, the embossed pattern <NUM> is formed up to the end of a sealed portion. Consequently, the adhesion area between the upper case <NUM> and the lower case <NUM> on the sealed portion <NUM> may be wider, whereby sealing force may be further improved.

Meanwhile, the battery cell <NUM> is configured such that the embossed pattern formed on the overall width direction (W) sealed portion and the embossed pattern formed on the overall length direction (H) sealed portion are different in size and interval from each other. Consequently, it is possible to freely set the size and interval of the embossed pattern in order to secure desired sealing force.

A description of the battery cell <NUM> may be equally applied to the other parts of the battery cell <NUM>, and therefore a detailed description thereof will be omitted.

<FIG> is a vertical sectional view of a sealed portion of a battery cell.

Referring to <FIG>, three types of embossed patterns are shown. For convenience of understanding, the upper case <NUM> and the lower case <NUM> are shown as being spaced apart from each other; however, these cases are brought into tight contact with each other without being spaced apart from each other to form a sealed portion.

The embossed pattern shown in (a) of <FIG> is configured such that polygonal shapes when viewed in vertical section are formed at regular intervals having regular sizes, such that relief parts when viewed from above the sealed portion are recess parts when viewed from under the sealed portion, and such that recess parts when viewed from above the sealed portion are relief parts when viewed from under the sealed portion.

The embossed pattern shown in (b) of <FIG> is configured such that polygonal shapes when viewed in vertical section are formed at regular intervals having regular sizes, such that reliefs and recesses are alternately repeated when viewed from above the sealed portion, and such that recesses and reliefs are alternately repeated when viewed from under the sealed portion at positions corresponding to the reliefs and the recesses.

The embossed pattern shown in (c) of <FIG> is configured such that semicircular shapes when viewed in vertical section are formed at regular intervals having regular sizes, such that the semicircular shapes are reliefs when viewed from above the sealed portion, and such that the semicircular shapes are recesses when viewed from under the sealed portion.

The embossed pattern according to the present invention is not limited to the shapes shown in <FIG>, and the embossed pattern may be formed at various intervals while having various shapes.

<FIG> is a vertical sectional view of a sealing block according to a third embodiment.

Referring to <FIG>, the sealing block according to the third embodiment is suitable for forming the embossed pattern shown in (a) of <FIG>. The sealing block according to the third embodiment includes an upper sealing block <NUM> disposed above a sealed portion of a pouch-shaped battery cell and a lower sealing block <NUM> disposed under the sealed portion of the pouch-shaped battery cell.

The upper sealing block <NUM> and the lower sealing block <NUM> are configured to be engaged with each other at positions at which the upper sealing block and the lower sealing block correspond to each other. Concave recesses <NUM> are formed based on a sealing surface <NUM>, and convex protrusions <NUM> are formed based on the sealing surface <NUM>.

When the sealed portion of the pouch-shaped battery cell is disposed between the upper sealing block <NUM> and the lower sealing block <NUM> and the sealed portion is pressed and heated, the embossed pattern shown in (a) of <FIG> is formed. The protrusions <NUM> may protrude toward the sealed portion of the pouch-shaped battery cell.

<FIG> is a vertical sectional view of a sealing block according to a fourth embodiment.

Referring to <FIG>, the sealing block according to the fourth embodiment is suitable for forming the embossed pattern shown in (b) of <FIG>. The sealing block according to the fourth embodiment includes an upper sealing block <NUM> disposed above a sealed portion of a pouch-shaped battery cell and a lower sealing block <NUM> disposed under the sealed portion of the pouch-shaped battery cell.

The protrusions <NUM> are configured such that portions protruding upwards toward the sealed portion of the pouch-shaped battery cell and portions protruding downwards toward the sealed portion of the pouch-shaped battery cell are alternately repeatedly arranged, and the recesses <NUM> are formed in the sealing blocks that face each other so as to be engaged with the protrusions <NUM>.

In the battery cell according to the present invention, the sealing force of the sealed portion is increased. In a battery module including the battery cell as a unit battery, therefore, the battery cell may not be vented even at larger internal pressure. Consequently, safety of the battery module may be improved.

Hereinafter, the present invention will be described with reference to examples. These examples are provided only for easier understanding.

A pouch-shaped battery cell was prepared, and an outer periphery of the pouch-shaped battery cell was sealed such that an embossed pattern was formed on the entirety of the sealed portion.

A pouch-shaped battery cell was prepared, and an outer periphery of the pouch-shaped battery cell was sealed such that the sealed portion was flat.

The maximum deformation amount and the maximum stress of each of the battery cells manufactured according to Experimental Example <NUM> and Experimental Example <NUM> were measured while an internal pressure of <NUM> MPa was applied thereto. The results of the maximum deformation amount structure simulation of Experimental Example <NUM> are shown in <FIG>, and the results of the maximum deformation amount structure simulation of Experimental Example <NUM> are shown in <FIG>. In addition, the results of the maximum stress structure simulation of Experimental Example <NUM> are shown in <FIG>, and the results of the maximum stress structure simulation of Experimental Example <NUM> are shown in <FIG>.

Structure simulation was performed using Meshfree, which is a CAE tool developed by Midas IT Co. Three-dimensional shapes were implemented using SolidWorks, which is a CAD program, and then structure simulation was performed on the respective shapes using Meshfree.

Referring to <FIG> and <FIG>, the maximum deformation amount of Experimental Example <NUM> is about <NUM>, and the maximum deformation amount of Experimental Example <NUM> is about <NUM>.

Referring to <FIG> and <FIG>, the maximum stress of Experimental Example <NUM> is about <NUM> N/mm<NUM>, and the maximum stress of Experimental Example <NUM> is about <NUM> N/mm<NUM>.

Experimental Example <NUM>, in which the embossed pattern was formed on the entirety of the sealed portion, exhibited a maximum deformation amount smaller than the maximum deformation amount of Experimental Example <NUM>, in which the sealed portion was flat, and therefore it can be seen that the pouch-shaped battery cell having the embossed pattern formed on the entirety of the sealed portion thereof has a harder structure having a small deformation amount with respect to an increase in internal pressure.

In addition, when the same internal pressure was applied, the maximum stress of Experimental Example <NUM> was measured to be smaller than the maximum stress of Experimental Example <NUM>. Consequently, it can be seen that the pouch-shaped battery cell having the embossed pattern formed on the entirety of the sealed portion thereof is capable of withstanding larger internal pressure.

It can be seen from the above results that, when the embossed pattern is formed on the entirety of the sealed portion of the pouch-shaped battery cell, sealing force is increased.

The maximum deformation amount and the maximum stress of each of the battery cells manufactured according to Experimental Example <NUM> and Experimental Example <NUM> were measured while an internal pressure of <NUM>. <NUM> MPa was applied thereto. The results of the maximum deformation amount structure simulation of Experimental Example <NUM> are shown in <FIG>, and the results of the maximum deformation amount structure simulation of Experimental Example <NUM> are shown in <FIG>. In addition, the results of the maximum stress structure simulation of Experimental Example <NUM> are shown in <FIG>, and the results of the maximum stress structure simulation of Experimental Example <NUM> are shown in <FIG>.

Structure simulation was performed using the same method as in the maximum deformation amount and maximum stress measurement <NUM>.

Referring to <FIG>, the maximum deformation amount of Experimental Example <NUM> is about <NUM>, and the maximum deformation amount of Experimental Example <NUM> is about <NUM>. The maximum stress of Experimental Example <NUM> is about <NUM> N/mm<NUM>, and the maximum stress of Experimental Example <NUM> is about <NUM> N/mm<NUM>.

Experimental Example <NUM>, in which the embossed pattern was formed on the entirety of the sealed portion, exhibited the maximum deformation amount and the maximum stress smaller than the maximum deformation amount and the maximum stress of Experimental Example <NUM>, in which the sealed portion was flat.

When the embossed pattern is formed on the entirety of the sealed portion of the pouch-shaped battery cell, therefore, the pouch-shaped battery cell may have a harder structure, and sealing force may be maintained even when internal pressure is more greatly increased.

Claim 1:
A battery cell (<NUM>) comprising a pouch-shaped battery case (<NUM>) configured to receive an electrode assembly therein, wherein
the pouch-shaped battery case includes a sealed portion (<NUM>) provided at an outer periphery thereof surrounding an electrode assembly receiving portion, and
an embossed pattern (<NUM>) is formed on the sealed portion in all directions,
characterized in that intervals of the embossed pattern formed on the sealed portion in a direction in which an electrode lead (<NUM>) protrudes are formed at smaller intervals than intervals of the embossed pattern formed on the sealed portion in a direction in which no electrode lead protrudes.