Patent Description:
In general, secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, lithium ion batteries, and lithium ion polymer batteries. Such a secondary battery is being applied to and used in small-sized products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, E-bikes, and the like as well as large-sized products requiring high power such as electric vehicles and hybrid vehicles, power storage devices for storing surplus power or renewable energy, and backup power storage devices.

In order to manufacture an electrode assembly, a cathode, a separator, and an anode are manufactured and stacked. Specifically, cathode active material slurry is applied to a cathode collector, and anode active material slurry is applied to an anode collector to manufacture a cathode and an anode. Also, when the separator is interposed and stacked between the manufactured cathode and anode, unit cells are formed. The unit cells are stacked on each other to form an electrode assembly. Also, when the electrode assembly is accommodated in a specific case, and an electrolyte is injected, the secondary battery is manufactured.

Such a secondary battery is classified into a pouch type secondary battery and a can type secondary battery according to a material of a battery case accommodating an electrode assembly. In the pouch type secondary battery, the electrode assembly is accommodated in a pouch made of a flexible polymer material having a variable shape. Also, in the can type secondary battery, an electrode assembly is accommodated in a case made of a metal or plastic material having a predetermined shape. A pouch-type secondary battery is disclosed in <CIT>, in <CIT> and in <CIT>.

The pouch type battery case is manufactured by performing drawing molding on a pouch film having flexibility to form a cup part. The drawing molding is performed by inserting a pouch film into a press and applying a pressure to the pouch film through a punch to stretch the pouch film. In addition, when the cup part is formed, an electrode assembly is accommodated in an accommodation space of the cup part, and then, the battery case is folded to seal a sealing part, thereby manufacturing a secondary battery.

When the cup part is molded in the pouch film, two cup parts that are symmetrical to each other may be drawn and molded to be adjacent to each other in one pouch film. Also, the electrode assembly may be accommodated in the accommodation space of the one cup part, and then, the battery case may be folded so that the two cup parts face each other. As a result, since the two cup parts accommodate the one electrode assembly, the electrode assembly having a thickness thicker than of an electrode assembly accommodated in one cup part. Also, since the battery case is folded to form one edge of the secondary battery, only three edges except for the one edge may be sealed when a sealing process is performed later. Thus, the number of edges to be sealed may be reduced to improve a process rate and reduce the number of trimming processes.

<FIG> is a plan view of a pouch type secondary battery <NUM> according to the related art.

When a battery case is folded, and heat and a pressure are applied to seal the battery case, a portion of folded one edge of the secondary battery <NUM>, i.e., a portion of a folding part <NUM> protrudes to the outside. This is called a bat ear <NUM>.

As illustrated in <FIG>, when the bat ear <NUM> protrudes, an unnecessary volume further increases, and thus an error occurs in a designed size of the secondary battery <NUM>. Thus, when assembling the secondary batteries <NUM> to manufacture a battery module or the like, there is a problem in that it is not easy to assembly the secondary batteries <NUM>, and each of the secondary batteries <NUM> has to be designed with a small size from the beginning. Also, since the volume of the secondary battery <NUM> increases as a whole, there is also a problem in that energy density to the volume decreases.

An object to be achieved by the present invention is to provide a battery case for a secondary battery, which is capable of reducing an error in size and increasing in energy density to a volume, and a pouch type secondary battery.

The objects of the present invention are not limited to the aforementioned object, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below.

A pouch type battery case for a secondary battery, which accommodates an electrode assembly, in which electrodes and separators are stacked, according to an embodiment of the present invention for achieving the above object comprises: a first cup part and a second cup part, which are defined to recessed in a pouch film, respectively; an accommodation part, which is provided in a longitudinal direction of edges of the first cup part and the second cup part, which face each other, between the first cup part and the second cup part and in which one side of the electrode assembly is accommodated; an inclined part extending from both ends of the accommodation part and provided to be recessed in the pouch film; and a line forming part extending linearly from an outer end of the inclined part and provided to be recessed in the pouch film in the same direction as the longitudinal direction of the accommodation part.

In addition, in the inclined part, a ratio of a height up to the outer end to a length of an edge shared with an edge of one end of the accommodation part is greater than <NUM>.

In addition, in the inclined part, a ratio of the height up to the outer end to the length of the edge shared with the edge of the one end of the accommodation part is less than <NUM>.

In addition, the inclined part may have a polygonal shape and is recessed in the pouch film.

In addition, the inclined part may have a triangular or trapezoidal shape.

In addition, the inclined part may be recessed in an isosceles triangular shape.

In addition, in the inclined part, a vertex having the polygonal shape may be chamfered or filleted.

In addition, the inclined part may have a depth that gradually decreases from the accommodation part to the line forming part.

In addition, the line forming part may be recessed up to an edge of one side of the pouch film.

In addition, the line forming part may be recessed in a V shape.

In addition, the line forming part may be recessed in a U shape.

In addition, the accommodation part, the inclined part, and the line forming part may be formed together through one drawing process.

A pouch type secondary battery according to an embodiment of the present invention for achieving the above object includes: an electrode assembly, in which electrodes and separators are stacked; and a battery case configured to accommodate the electrode assembly therein, wherein the battery case includes: a first cup part and a second cup part, which are defined to recessed in a pouch film, respectively; an accommodation part, which is provided in a longitudinal direction of edges of the first cup part and the second cup part, which face each other, between the first cup part and the second cup part and in which one side of the electrode assembly is accommodated; an inclined part extending from both ends of the accommodation part and provided to be recessed in the pouch film; and a line forming part extending linearly from an outer end of the inclined part and provided to be recessed in the pouch film in the same direction as the longitudinal direction of the accommodation part.

Particularities of other embodiments are included in the detailed description and drawings.

The embodiments of the present invention may have at least the following effects.

The bat ear may be prevented from protruding outward more than the bottom surface of the accommodation part to reduce the error occurring in the designed size of the secondary battery, and the secondary batteries may be easily assembled to manufacture the battery module.

In addition, since the unnecessary volume of the secondary battery decreases as a whole, the energy density to the volume may increase.

In addition, since the shapes of the cup part, the sealing part, and the inclined part are maintained without being deformed, and the battery case is folded, the electrode assembly may be stably accommodated in the cup part.

In addition, since the sealing parts of the battery case accurately contact each other and then are sealed, the sealing parts may be firmly sealed.

In addition, the bottom surface of the accommodation part may be prevented from being wrinkled.

The effects of the present invention are not limited by the aforementioned description, and thus, more varied effects are involved in this specification.

Advantages and features of the present invention, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. The present invention may, however be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Further, the present invention is only defined by scopes of claims.

Unless terms used in the present invention are defined differently, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art. Also, unless defined clearly and apparently in the description, the terms as defined in a commonly used dictionary are not ideally or excessively construed as having formal meaning.

In the following description, the technical terms are used only for explaining a specific exemplary embodiment while not limiting the present invention. In this specification, the terms of a singular form may include plural forms unless specifically mentioned. The meaning of "comprises" and/or "including" does not exclude other components besides a mentioned component.

<FIG> is an assembly view of a pouch type secondary battery <NUM> according to an embodiment of the present invention, and <FIG> is a perspective view of the pouch type secondary battery <NUM> according to an embodiment of the present invention.

As illustrated in <FIG>, the pouch type secondary battery <NUM> according to an embodiment of the present invention includes a pouch type battery case <NUM> and an electrode assembly <NUM> accommodated in the battery case <NUM>.

The electrode assembly <NUM> may be a stacked structure including two electrodes such as a cathode and an anode and a separator interposed between the electrodes to insulate the electrodes from each other or disposed at a left or right side of one electrode. The stacked structure may have various shapes without being limited in shape. For example, the cathode and the anode, each of which has a predetermined standard, may be stacked with the separator therebetween, or the stacked structure may be wound in the form of a jelly roll. Each of the two electrodes has a structure in which active material slurry is applied to a metal foil or a mesh-shaped collector including aluminum and copper. The slurry may be usually formed by agitating a granular active material, an auxiliary conductor, a binder, and a plasticizer with a solvent added. The solvent may be removed in the subsequent process.

As illustrated in <FIG>, the electrode assembly <NUM> includes the electrode tabs <NUM>. The electrode tabs <NUM> are respectively connected to a positive electrode and a negative electrode of the electrode assembly <NUM> to protrude to the outside of the electrode assembly <NUM>, thereby providing a path, through which electrons are moved, between the inside and outside of the electrode assembly <NUM>. A collector of the electrode assembly <NUM> is constituted by a portion coated with an electrode active material and a distal end, on which the electrode active material is not applied, i.e., a non-coating portion. Also, each of the electrode tabs <NUM> may be formed by cutting the non-coating portion or by connecting a separate conductive member to the non-coating portion through ultrasonic welding. As illustrated in <FIG>, the electrode tabs <NUM> may protrude in each of different directions of the electrode assembly <NUM>, but is not limited thereto. For example, the electrode tabs may protrude in parallel to each other from one side in the same direction.

In the electrode assembly <NUM>, the electrode lead <NUM> is connected to the electrode tab <NUM> through spot welding. Also, a portion of the electrode lead <NUM> is surrounded by an insulation part <NUM>. An insulation part <NUM> may be disposed to be limited within a sealing part <NUM>, at which a first case <NUM> and a second case <NUM> are thermally fused, so as to be bonded to the battery case <NUM>. Also, electricity generated from the electrode assembly <NUM> may be prevented from flowing to the battery case <NUM> through the electrode lead <NUM>, and the sealing of the battery case <NUM> may be maintained. Thus, the insulation part <NUM> may be made of a nonconductor having non-conductivity, which is not electrically conductive. In general, although an insulation tape which is easily attached to the electrode lead <NUM> and has a relatively thin thickness is mainly used as the insulation part <NUM>, the present invention is not limited thereto. For example, various members may be used as the insulation part <NUM> as long as the members are capable of insulating the electrode lead <NUM>.

The electrode lead <NUM> may extend in different directions or extend in the same direction according to the formation positions of the positive electrode tab <NUM> and the negative electrode tab <NUM>. The positive electrode lead <NUM> and the negative electrode lead <NUM> may be made of materials different from each other. That is, the cathode lead <NUM> may be made of the same material as the cathode plate, i.e., an aluminum (Al) material, and the anode lead <NUM> may be made of the same material as the anode plate, i.e., a copper (Cu) material or a copper material coated with nickel (Ni). Also, a portion of the electrode lead <NUM>, which protrudes to the outside of the battery case <NUM>, may be provided as a terminal part and electrically connected to an external terminal.

The battery case <NUM> is a pouch made of a flexible material and is manufactured by performing drawing molding on the pouch film having flexibility to form a cup part <NUM>. Also, the battery case <NUM> accommodates the electrode assembly <NUM> so that a portion of the electrode lead <NUM>, i.e., the terminal part is exposed and then is sealed. As illustrated in <FIG>, the battery case <NUM> includes a first case <NUM> and a second case <NUM>. A first cup part <NUM> and a second cup part <NUM> are respectively provided in the first case <NUM> and the second case <NUM> to provide an accommodation space in which the electrode assembly <NUM> is accommodated. Also, the battery case <NUM> is folded to allow the electrode assembly <NUM> to be accommodated in the accommodation space of the cup part <NUM>, thereby preventing the electrode assembly <NUM> from being separated to the outside of the battery case <NUM>.

When the two cup parts <NUM> are drawn and molded to be symmetrical to each other in the pouch film, an accommodation part <NUM> may be drawn and molded together between the two cup parts <NUM>. As illustrated in <FIG>, the accommodation part <NUM> is a space which is lengthily defined in a longitudinal direction of edges of the first cup part <NUM> and the second cup part <NUM>, which face each other, and in which the electrode assembly <NUM> is accommodated first, between the first cup part <NUM> and the second cup part <NUM>. The accommodation part <NUM> accommodates one side of the electrode assembly <NUM> first to fix a position of the one side of the electrode assembly <NUM> so that the electrode assembly <NUM> is easily accommodated in the cup part <NUM>. For this, as illustrated in <FIG>, the accommodation part <NUM> has a width W and length I, which respectively correspond to a thickness T and length L of the electrode assembly <NUM> and is disposed at a position spaced the same distance from the first cup part <NUM> and the second cup part <NUM>. Thus, a central axis defined in a longitudinal direction of the accommodation part <NUM> functions as a symmetrical axis of the first cup part <NUM> and the second cup part <NUM>.

When the electrode lead <NUM> is connected to the electrode tab <NUM> of the electrode assembly <NUM>, and the insulation part <NUM> is disposed on a portion of the electrode lead <NUM>, the electrode assembly <NUM> is accommodated in the accommodation part <NUM>. Also, when the first case <NUM> and the second case <NUM> are folded, the electrode assembly <NUM> is accommodated in the accommodation space provided in the first and second cup parts <NUM> and <NUM>, and then, the first and second cup parts <NUM> and <NUM> surround the electrode assembly <NUM>. Also, an electrolyte is injected into the accommodation space, and sealing parts <NUM> disposed on edges of the first case <NUM> and the second case <NUM> are sealed. The electrolyte may move lithium ions generated by electrochemical reaction of the electrode during charging and discharging of the secondary battery <NUM>. The electrolyte may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and a high-purity organic solvent or a polymer using a polymer electrolyte. As illustrated in <FIG>, the pouch type secondary battery <NUM> may be manufactured through the above-described method.

<FIG> is a cross-sectional view of the pouch type battery case <NUM>, taken along line A-A' of <FIG>, according to an embodiment of the present invention.

As illustrated in <FIG>, the cup part <NUM> has a shape in which a depth d gradually increases from a portion <NUM> corresponding to a central portion of the width W of the electrode assembly <NUM> toward a portion <NUM> corresponding to an upper edge of the electrode assembly <NUM>. Also, a section between the accommodation part <NUM> and the cup part <NUM> has a flat shape with little change in depth.

The deepest depth d in the cup part <NUM> is a portion corresponding to the upper edge of the electrode assembly <NUM>, and the depth d is preferably deeper than half of the thickness T of the electrode assembly <NUM>. Thereafter, when the first and second cup parts <NUM> and <NUM> face each other, and the sealing parts <NUM> of the battery case <NUM> are sealed, the cup part <NUM> accommodates the electrode assembly <NUM> therein. However, if the depth d of each of the first cup part <NUM> and the second cup part <NUM> is not deeper than half of the thickness T of the electrode assembly <NUM>, after the first cup part <NUM> and the second cup part <NUM> accommodate the electrode assembly <NUM> therein, the sealing parts <NUM> may not contact each other so as not to be sealed, or even if the sealing parts contact each other, a contact area is too narrow to cause sealing failure.

A section between the accommodation part <NUM> and the cup part <NUM> has a length S that varies according to the width W and thickness T of the electrode assembly <NUM>. That is, it is preferable that the shorter the width W of the electrode assembly <NUM>, the shorter the length S of the section between the accommodation part <NUM> and the cup part <NUM>. On the other hand, it is preferable that the longer the width W of the electrode assembly <NUM>, the longer the length S of the section between the accommodation part <NUM> and the cup part <NUM>. Also, since the thicker the thickness T of the electrode assembly <NUM>, the deeper the depth d of the cup part <NUM>, it is preferable that that the length S of the section between the accommodation part <NUM> and the cup part <NUM> is shortened. On the other hand, since the thinner the thickness T of the electrode assembly <NUM>, the shallower the depth d of the cup part <NUM>, it is preferable that the length S of the section between the accommodation part <NUM> and the cup part <NUM> is longer.

<FIG> is a cross-sectional view illustrating a state in which the electrode assembly <NUM> is being accommodated in the pouch type battery case <NUM> of <FIG>, and <FIG> is a cross-sectional view illustrating a state in which the electrode assembly <NUM> is accommodated in the pouch type battery case <NUM> of <FIG>.

The accommodation part <NUM> accommodates one side of the electrode assembly <NUM>. Here, as illustrated in <FIG> and <FIG>, it is preferable that the electrode assembly <NUM> is accommodated upright from the top to the bottom. Thus, when the battery case <NUM> is folded later, the first and second cup parts <NUM> and <NUM> respectively disposed on both sides of the electrode assembly <NUM> may surround the electrode assembly <NUM> to accommodate the electrode assembly <NUM> therein.

As described above, since the accommodation part <NUM> has the width W and length I, which respectively correspond to the thickness T and length L of the electrode assembly <NUM>, as illustrated in <FIG>, the electrode assembly <NUM> may be easily accommodated in the accommodation part <NUM> and then fixed in position.

<FIG> is a cross-sectional view illustrating a state in which the pouch type battery case <NUM> of <FIG> is being folded, and <FIG> is a cross-sectional view illustrating a state in which the pouch type battery case <NUM> of <FIG> is folded.

After the electrode assembly <NUM> is accommodated in the accommodation part <NUM>, the first case <NUM> and the second case <NUM>, which are respectively disposed at both sides of the accommodation part <NUM>, are folded upward as illustrated in <FIG>. As a result, as illustrated in <FIG>, the two cup parts <NUM> may face each other to surround the electrode assembly <NUM> so that the electrode assembly <NUM> is accommodated in the accommodation space provided in the cup parts <NUM>.

As illustrated in <FIG>, the first case <NUM> and the second case <NUM> are respectively bent and connected at substantially right angles from both sidewalls that define the accommodating part <NUM>. Also, when the first case <NUM> and the second case <NUM> are folded, the first and second cases <NUM> and <NUM>, which are bent as illustrated in <FIG>, are unfolded from both sidewalls of the accommodation part <NUM> to accommodate the electrode assembly <NUM> in the cup part <NUM>. That is, the battery case <NUM> is folded when viewed as a whole, but the bent portion is unfolded when viewed from both the sidewalls of the accommodation part <NUM>.

As described above, after the first case <NUM> and the second case <NUM> are folded, when the sealing part <NUM> is sealed using a sealing tool, the secondary battery <NUM> is completely manufactured.

<FIG> is an enlarged perspective view of a line forming part <NUM> according to an embodiment of the present invention.

According to an embodiment of the present invention, the bat ear <NUM> may be prevented from protruding outward more than a bottom surface of the accommodation part to reduce an error that occurs in a designed size of the secondary battery <NUM>, and thus, the secondary batteries <NUM> may be easily assembled to form a battery module. Also, since the secondary battery <NUM> is unnecessarily reduced in volume as a whole, energy density to a volume may increase. Also, since the shapes of the cup part <NUM>, the sealing part <NUM>, and the inclined part <NUM> are maintained without being deformed, and the battery case <NUM> is folded, the electrode assembly <NUM> may be stably accommodated in the cup part <NUM>. Also, since the sealing parts <NUM> of the battery case <NUM> accurately contact each other and then are sealed, the sealing parts <NUM> may be firmly sealed. In addition, the bottom surface of the accommodation part may be prevented from being wrinkled.

For this, the pouch type battery case <NUM> for the secondary battery <NUM>, which accommodates an electrode assembly, in which electrodes and separators are stacked, according to an embodiment of the present invention includes: a first cup part <NUM> and a second cup part <NUM>, which are defined to recessed in a pouch film, respectively; an accommodation part <NUM>, which is provided in a longitudinal direction of edges of the first cup part <NUM> and the second cup part <NUM>, which face each other, between the first cup part <NUM> and the second cup part <NUM> and in which one side of the electrode assembly <NUM> is accommodated; an inclined part <NUM> extending from both ends of the accommodation part <NUM> and provided to be recessed in the pouch film; and a line forming part <NUM> extending linearly from an outer end <NUM> of the inclined part <NUM> and provided to be recessed in the pouch film in the same direction as the longitudinal direction of the accommodation part <NUM>.

As described above, the accommodation part <NUM> is lengthily defined in a longitudinal direction of edges of the first cup part <NUM> and the second cup part <NUM>, which face each other, between the first cup part <NUM> and the second cup part <NUM>, and one side of the electrode assembly <NUM> is accommodated in the accommodation part <NUM>. The accommodation part <NUM> is disposed to be spaced the same distance from the two cup parts <NUM>, has a substantially rectangular shape, and is recessed lengthily to one side in the pouch film. Thus, a central axis defined in a longitudinal direction of the accommodation part <NUM> functions as a symmetrical axis of the two cup parts <NUM>.

The inclined part <NUM> extends from both ends of the accommodation part <NUM> and is recessed in the pouch film. The inclined part <NUM> may have a triangular or trapezoidal polygon when viewed from an upper side of the pouch film and may be recessed in an isosceles triangle shape. Also, an edge corresponding to a bottom side of the inclined part <NUM> shares the same edge as edges corresponding to both ends of the accommodation part <NUM>. However, the present invention is not limited thereto, and the inclined part <NUM> may have various shapes such as a semicircle or a semi-ellipse shape when viewed from above.

The inclined part <NUM> has the same depth as the accommodation part <NUM> at the accommodation part <NUM> and gradually decreases in depth from the accommodation part <NUM> toward the line forming part <NUM>. In addition, the inclined part <NUM> may be smoothly connected to the line forming part <NUM> at an outer end <NUM> (see <FIG>) thereof and have the same depth as the line forming part <NUM>. Thus, when viewed from a side surface of the pouch film, the inclined part <NUM> may have a substantially right triangle shape.

The line forming part <NUM> extends linearly from the outer end <NUM> of the inclined part <NUM> and is recessed in the pouch film in the same direction as the longitudinal direction of the accommodation part <NUM>. If the line forming part <NUM> is not provided, and the battery case <NUM> is simply folded, the first cup part <NUM> and the second cup part <NUM> may not face each other exactly, but may face each other to be misaligned with each other. As a result, the space inside the first cup part <NUM> and the second cup part <NUM>, in which the electrode assembly <NUM> is accommodated may be deformed, and the shape of the sealing part <NUM> and the inclined part <NUM> may also modified. Therefore, there is a problem that the electrode assembly <NUM> is not stably accommodated. Also, since the sealing parts <NUM> of the battery case <NUM> do not exactly contact each other, the sealing may not be performed, or an area of the sealing part <NUM> may be excessively narrowed, resulting in poor sealing.

Therefore, according to an embodiment of the present invention, since the line forming part <NUM> is provided, and the battery case <NUM> is folded along the line forming part <NUM>, the line forming part <NUM> guides the folding of the battery case <NUM>. As a result, since the shapes of the cup part <NUM>, the sealing part <NUM>, and the inclined part <NUM> are maintained without being deformed, and the battery case <NUM> is folded, the electrode assembly <NUM> may be stably accommodated in the cup part <NUM>. Also, since the sealing parts <NUM> of the battery case <NUM> accurately contact each other and then are sealed, the sealing parts <NUM> may be firmly sealed.

Since the line forming part <NUM> guides the folding of the battery case <NUM>, the battery case <NUM> is folded with respect to the line forming part <NUM>. Then, when the battery case <NUM> is folded, and the secondary battery <NUM> is completed, the folding part <NUM> that is a portion of the battery case <NUM>, which is directly folded, is disposed at a position at which the line forming part <NUM> has been provided. The line forming part <NUM> may be recessed from the outer end <NUM> of the inclined part <NUM> to one edge of the pouch film. Thus, the battery case <NUM> may be folded more easily.

<FIG> is an enlarged plan view of the inclined part and the line forming part according to an embodiment of the present invention.

As described above, the inclined part <NUM> has a polygonal shape and may be recessed in the pouch film in a triangular or trapezoidal shape. Here, the formation of the polygonal shape is not limited to the dictionary meaning of the polygon, that is, a planar configuration having plural vertexes and straight edges. As illustrated in <FIG>, the inclined part <NUM> may have various shapes as long as the inclined part <NUM> has a substantially polygonal shape without being limited to cases in which when the outer end <NUM> of the inclined part <NUM> partially overlaps the line forming part <NUM>, and thus, at least one vertex is chamfered, or two vertexes defining both ends of the edge <NUM> corresponding to the bottom side of the inclined part are filleted.

As illustrated in <FIG>, the inclined part <NUM> may be recessed in an isosceles triangular shape when the pouch film is viewed from above. That is, the two edges from both the ends of the edge <NUM> corresponding to the bottom side of the inclined part <NUM> to the outer end <NUM> of the inclined part <NUM> may have the same length. Here, the edge <NUM> corresponding to the bottom side of the inclined part <NUM> shares the same edge as one end of the accommodation part <NUM> when the pouch film is viewed from above.

In the triangular or trapezoidal shape of the inclined part <NUM>, the ratio of a height h up to the outer end <NUM> to a depth D of the edge shared with the edge <NUM> corresponding to the bottom side, i.e., the edge of the one end of the accommodation part <NUM> ranges of <NUM> to <NUM>. If the ratio is less than <NUM>, the folding part <NUM> may be provided from a position that is close to the accommodation part <NUM> until the battery case <NUM> is folded later. Therefore, since an area of the sealing part, on which the bat ear <NUM> is to be formed, is sufficient, and an angle between the accommodation part <NUM> and the bat ear <NUM> is sharply changed, the bat ear <NUM> protrudes outward as ever more than a height of the accommodation part <NUM> or protrudes as ever up to a height similar to that of the accommodation part <NUM>. Also, a problem that a bottom surface <NUM> of the accommodation part <NUM> is still wrinkled may occur. When the ratio is greater than <NUM>, since the height of the inclined part <NUM> is excessively long, and a dead space increases after manufacturing the secondary battery <NUM>, energy efficiency to a volume may decrease. Also, the electrode assembly <NUM> is not fixed to move inside the battery case <NUM>, thereby deteriorating stability.

Here, it is preferable that a length D of an edge shared with the edge of the one end of the accommodation part <NUM> is the same as a width W of the accommodation part.

As illustrated in <FIG>, all the accommodation part <NUM>, the inclined part <NUM> and the line forming part <NUM> are connected to each other. Therefore, the accommodation part <NUM>, the inclined part <NUM>, and the line forming part <NUM> are not separately formed, but be formed together in one drawing process on the pouch film. Therefore, the number of drawing processes performed on the pouch film may be reduced to increase in process rate.

<FIG> is a partially enlarged side view of the battery case according to the related art.

The folding part <NUM> is a portion that is directly folded at both ends of the accommodation part <NUM> in the battery case <NUM> when the battery case <NUM> is folded. Also, when the secondary battery <NUM> is viewed from the side, a recess part <NUM> in which an area between both the ends of the accommodation part <NUM> and the folding part <NUM> is recessed inward may be defined. However, in the related art, as illustrated in <FIG>, since the inclined part <NUM> is not provided, the recess part <NUM> is defined approximately vertically at both the ends of the accommodation part <NUM>. Then, the folding part <NUM> is provided from a position that is very close to the accommodation part <NUM>, and thus, the area of the sealing part <NUM>, on which the bat ear <NUM> is to be formed is sufficient, and an angle between the accommodation part <NUM> and the bat ear <NUM> is sharply changed. Thus, the bat ear <NUM> may protrude outward more than the bottom surface <NUM> of the accommodation part <NUM>. Also, a problem that a bottom surface <NUM> of the accommodation part <NUM> is wrinkled may occur.

<FIG> is a partially enlarged side view of the battery case <NUM> according to an embodiment of the present invention.

As described above, since the inclined part <NUM> gradually decreases in depth from the accommodation part <NUM> toward the line forming part <NUM>, when the inclined part <NUM> extends from both the ends of the accommodation part <NUM>, the recess part <NUM> is recessed inward to a certain inclination. Then, as illustrated in <FIG>, the folding part <NUM> is disposed at a position spaced apart from the accommodation part <NUM> to reduce the area of the sealing part <NUM>, which is capable of forming the bat ear <NUM>. Also, the angle between the accommodation part <NUM> and the bat ear <NUM> is changed gently to a certain degree. Thus, the bat ear <NUM> may be prevented from protruding outward more than the bottom surface <NUM> of the accommodation part <NUM>. Also, the bottom surface <NUM> of the accommodation part <NUM> may be prevented from being wrinkled.

<FIG> is an enlarged front view of the line forming part according to an embodiment of the present invention.

As described above, the line forming part <NUM> is recessed in the pouch film in a straight-line shape to guide the folding of the battery case <NUM>. Here, according to an embodiment of the present invention, the line forming part <NUM> may be recessed in a V shape as illustrated in <FIG> to more easily guide the folding of the battery case <NUM>. As a result, when the battery case <NUM> is folded, since the battery case <NUM> is folded with respect to a bent portion of the lowermost end of the line forming part <NUM>, the shapes of the cup part <NUM>, the sealing part <NUM>, and the inclined part <NUM> may not be deformed but be firmly maintained, and thus, the battery case <NUM> may be easily folded.

<FIG> is an enlarged front view of a line forming part according to another embodiment of the present invention.

If a thickness of a pouch film is considerably thin, when a line forming part <NUM> is drawn and molded in a V shape, a bent portion of the lowermost end of the line forming part <NUM> may be damaged. Therefore, according to another embodiment of the present invention, when a thickness of the pouch film is considerably thin, the line forming part 138a may be recessed in a U shape, as illustrated in <FIG>. As a result, the folding of the battery case 13a may be guided while preventing the pouch film from being damaged.

First, a pouch film manufactured by sequentially stacking polypropylene (PP), aluminum (Al), and polyethylene terephthalate (PET) was prepared. Then, drawing molding was performed on the pouch film to form a first cup part, a second cup part, and an accommodation part. The first cup part and the second cup part were formed to be symmetrical to each other, and the accommodation part was formed lengthily between the first cup part and the second cup part in a longitudinal direction of edges facing each other. Each of the first cup part and the second cup part has a depth d of <NUM>, and a length S of a section between the accommodation part and the cup part is <NUM>. Also, a length <NUM> of the accommodation part is <NUM>, and a width W of the accommodation part is <NUM>.

When drawing the accommodation part, an inclined part extending from both ends of the accommodation part and a line forming part extending in a straight-line shape from an outer end of the inclined part were drawn and molded together. When molding the inclined part, the inclined part was molded so as to have a triangular shape when viewed from the above and gradually decrease in depth from the accommodation part toward the line forming part. Also, when molding the line forming part, the line forming part was molded in the same direction as a longitudinal direction of the accommodation part. In the inclined part, an edge shared with an edge of one end of the accommodation part has a length D of <NUM>, and a height h up to an outer edge is <NUM>. Accordingly, a ratio of the height h up to the outer end to the length D of the edge shared with the edge of the one end of the accommodation part is <NUM>, i.e., ranges of <NUM> to <NUM>. Also, when molding the line forming part, the line forming part was molded in a V shape.

The electrode assembly was accommodated upright from the top to the bottom in the accommodation part. The electrode assembly has a length L of <NUM>, a width W of <NUM>, and a thickness T of <NUM>. After the electrode assembly is accommodated in the accommodation part, the first case and the second case on both sides of the accommodation part were folded upward. Thereafter, the remaining edges except for the folded one edge was sealed using a sealing tool to manufacture a secondary battery.

It was manufactured in the same manner as Manufacturing Example <NUM>, except that a height h up to an outer end of an inclined part is <NUM>. Accordingly, a ratio of the height h up to the outer end to a length D of an edge shared with an edge of one end of an accommodation part is <NUM>, i.e., ranges of <NUM> to <NUM>.

It was manufactured in the same manner as Manufacturing Example <NUM>, except that an inclined part and a line forming part are not molded.

In the secondary battery manufactured in Manufacturing Example <NUM>, Manufacturing Example <NUM>, and Comparative Example, a difference between the height of the bottom surface of the accommodation part and the bat ear was measured.

In the secondary battery according to Comparative Example, since the inclined part is not formed, the folding part is formed at a position that is close to the accommodation part. Accordingly, a recess part is formed approximately vertically at both ends of the accommodation part. Also, an area of the sealing part, which is capable of forming the bat ear, is sufficiently large, and an angle between the accommodation part and the bat ear is changed sharply. Therefore, a difference t1 in height between the bat ear and the accommodation part is <NUM>, and the bat ear protrudes to a height approximately similar to that of the accommodation part.

On the other hand, in the secondary battery according to Manufacturing Example <NUM> and Manufacturing Example <NUM>, since the inclined part is formed, the folding part is formed at a position spaced a certain distance from the accommodation part. Thus, the recess part is recessed inward at a certain inclination. Also, the area of the sealing part, which is capable of forming the bat ear, is reduced, and an angle between the accommodation part and the bat ear is changed gently to a certain degree. Therefore, according to Manufacturing Example <NUM>, a difference t2 in height between the bat ear and the accommodation part is <NUM>. According to Manufacturing Example <NUM>, a difference t2 in height between the bat ear and the accommodation part is -<NUM>. That is, the bat ear protruding outward may be reduced in height to reduce an error occurring in a designed size of the secondary battery, and the secondary batteries may be easily assembled to manufacture the battery module.

Claim 1:
A pouch type battery case (<NUM>) for a secondary battery, which accommodates an electrode assembly (<NUM>), in which electrodes and separators are stacked, the battery case (<NUM>) comprising:
a first cup part (<NUM>) and a second cup part (<NUM>), which are defined to recessed in a pouch film, respectively;
an accommodation part (<NUM>), which is provided in a longitudinal direction of edges of the first cup part (<NUM>) and the second cup part (<NUM>), which face each other, between the first cup part (<NUM>) and the second cup part (<NUM>) and in which one side of the electrode assembly (<NUM>) can be accommodated;
an inclined part (<NUM>) extending from both ends of the accommodation part (<NUM>) and provided to be recessed in the pouch film; and
a line forming part (<NUM>) extending linearly from an outer end of the inclined part (<NUM>) and provided to be recessed in the pouch film in the same direction as the longitudinal direction of the accommodation part (<NUM>),
wherein, in the inclined part (<NUM>), a ratio of a height up to the outer end to a length of an edge shared with an edge of one end of the accommodation part (<NUM>) is greater than <NUM>, and
wherein, in the inclined part (<NUM>), a ratio of the height up to the outer end to the length of the edge shared with the edge of the one end of the accommodation part (<NUM>) is less than <NUM>.