Pouch-Type Battery Case, Apparatus for Manufacturing the Same, and Pouch-Type Secondary Battery

A pouch-type battery case according to an embodiment of the invention may accommodate an electrode assembly, in which electrodes and separators are alternately stacked. The pouch-type battery case may include: a pair of recess parts, each of which has a recessed shape; a pair of terraces that are disposed around the pair of recess parts and are inclined downward in a direction closer to each other in a state; in which the battery case is unfolded; and a bridge disposed between the pair of recess parts, configured to connect the pair of recess parts to each other, having a pair of connection surfaces formed to be inclined upward from a bottom surface of each of the pair of recess parts in a direction closer to each other. In the state in which the battery case is unfolded, an angle formed by the pair of terraces may be an obtuse angle.

TECHNICAL FIELD

The present invention relates to a pouch-type battery case, an apparatus for manufacturing the same, and a pouch-type secondary battery.

BACKGROUND ART

Secondary batteries that are repetitively chargeable and dischargeable may be divided into cylindrical type secondary batteries, prismatic type secondary batteries, and pouch-type secondary batteries according to their manufacturing methods or structures. Among them, in general, such a pouch-type secondary battery has an electrode assembly having a structure, in which electrodes and separators are alternately disposed in a sheet-shaped pouch exterior.

According to the related art, in order to manufacture the pouch-type secondary battery, a pouch-type battery case is manufactured through a forming process, in which a partial area of a pouch sheet is pressed by an area corresponding to an area of the electrode assembly to a recess part having a recessed shape. Thereafter, the electrode assembly is mounted in the recess part, and portions of the battery case are attached to each other to form a sealing part.

The sealing part is formed by attaching the portions of the partial areas of the pouch-type battery case to each other by attaching areas that are not pressed in the forming process. Thus, due to a height difference between the sealing part, on which the forming process is not performed, and an accommodation part, on which the forming process is performed, a portion of the sealing area is deviated from a width of the accommodation part.FIG.1illustrates a state in which a partial area of the sealing part3is formed at each of both sides in a longitudinal direction of the pouch-type secondary battery1, manufactured according to the related art, protrudes more than the width of the recess part2in which the electrode assembly is accommodated.

The protruding area as described above is generally referred to as a bat-ear. The bat-ear may act as a cause of an increase in dead space that is not contributed in capacity, resulting in causing a problem that energy densities of a battery cell and a secondary module are reduced.

In addition, according to the related art, since a void space is generated between an inner circumference of the recess part2and the electrode assembly, wrinkles occur in the battery case2after a degassing process.

DISCLOSURE OF THE INVENTION

Technical Problem

Accordingly, an object of the present invention for solving the above problem is to provide a pouch-type battery case in which a void space that is not occupied by an electrode assembly is reduced, and a pouch-type secondary battery including the same.

Another object of the present invention for solving the above problem is to provide a manufacturing apparatus capable of manufacturing the pouch-type battery case.

Technical Solution

A pouch-type battery case according to an embodiment of the present invention may accommodate an electrode assembly, in which electrodes and separators are alternately stacked. The pouch-type battery case may include: a pair of recess parts, each of which has a recessed shape; a pair of terraces that are disposed around the pair of recess parts and are inclined downward in a direction closer to each other in a state in which the battery case is unfolded; and a bridge disposed between the pair of recess parts, configured to connect the pair of recess parts to each other, having a pair of connection surfaces formed to be inclined upward from a bottom surface of each of the pair of recess parts in a direction closer to each other. In the state in which the battery case is unfolded, an angle formed by the pair of terraces may be an obtuse angle.

In the state in which the battery case is unfolded, the bottom surfaces of the pair of recess parts may be formed to be inclined upward in a direction away from each other.

In the state in which the battery case is unfolded, the angle formed by the pair of terraces may be 130 degrees to 170 degrees.

The pouch-type battery case may further include: an inner edge configured to connect an inner circumference of the recess part to the bottom surface of the recess part; and an outer edge configured to connect an outer circumference of each of the recess part to the terrace. The inner edge may have a curvature radius equal to or greater than a curvature radius of the outer edge.

In the state in which the battery case is unfolded, a clearance between the inner edge and the outer edge in a horizontal direction may be 0.5 mm or less.

In the state in which the battery case is unfolded, a clearance between the inner edge and the outer edge in a horizontal direction may be 0.35 mm or less.

In the state in which the battery case is unfolded, a clearance between the inner edge and the outer edge in a horizontal direction may be equal to or less than the curvature radius of the outer edge.

The pouch-type battery case may further include, in the state in which the battery case is unfolded, a bending part configured to connect the pair of terraces to each other and convexly rounded downward.

The bridge may further include a first connection edge configured to the pair of connection surfaces to each other and convexly rounded upward. A height of the lowermost end of the bending part may be equal to or greater than a height of the uppermost end of the first connection edge.

In the state in which the battery case is unfolded, the bridge may further include a pair of second connection edges configured to the pair of connection surfaces to the bottom surfaces of the pair of recess parts and convexly rounded downward.

In the state in which the battery case is unfolded, with respect to a virtual line passing through a boundary between the inner circumference of the recess part and the inner edge and perpendicular to each of the terraces, a distance from the virtual line to the connection surface in a direction parallel to the terrace may be a first distance, and a distance from the virtual line to a boundary between the terrace and the bending part may be a second distance less than the first distance.

In the state in which the battery case is unfolded, a length from a center of the bending part to the boundary between the terrace and the bending part may be less than a difference between the first distance and the second distance.

A pouch-type secondary battery may include: an electrode assembly in which electrodes and separators are alternately stacked; and the pouch-type battery case including an accommodation part configured to accommodate the electrode assembly. The case may include: a folding part configured to form a portion of a circumferential surface of the accommodation part; and a circumferential part expanded from the other portion of the circumferential surface of the accommodation part. An edge of the circumferential part may include: a first edge adjacent to the folding part; a second edge extending from the first edge in an opposite direction of the folding part and having a thickness less than that of the first edge; and a boundary part configured to connect the first edge to the folding part and protruding more than the first edge in a width direction of the accommodation part.

The first edge and the second edge may protrude less than the folding part in the width direction of the accommodation part.

The second edge may protrude more than the first edge in the width direction of the accommodation part.

The boundary part may protrude less than the folding part in the width direction of the accommodation part.

The pouch-type secondary battery may further include: an inner edge configured to an inner top surface or inner bottom surface of the accommodation part to an inner circumference of the accommodation part; and an outer edge configured to an outer circumference of the accommodation part to the circumferential part. The inner edge may have a curvature radius equal to or greater than a curvature radius of the outer edge.

A clearance between the inner edge and the outer edge in a horizontal direction may be equal to or less than the curvature radius of the outer edge.

An apparatus for manufacturing a pouch-type battery case may be formed by punching a pouch sheet seated on a die by using a punch. The die may include: a pair of seating surfaces inclined upward in a direction away from each other; a pair of forming parts recessed or penetrated downward from the pair of seating surfaces; and a center part disposed between the pair of forming parts. The punch may include a pair of punching parts inserted into the pair of forming parts and having bottom surfaces inclined in a direction, in which a height thereof decreases as the pair of punching parts are closer to each other. An angle formed by the pair of seating surfaces may be an obtuse angle.

The angle formed by the pair of seating surfaces may be 130 degrees to 170 degrees.

The die may further include a die edge configured to connect an inner circumference of each of the forming parts to each of the seating surfaces. The punch may further include a punching edge configured to connect an outer circumference of the punching part to a bottom surface of the punching part. The punching edge may have a curvature radius equal to or greater than a curvature radius of the die edge.

A clearance between the die edge and the punching edge in a horizontal direction may be 0.5 mm or less.

A clearance between the die edge and the punching edge in a horizontal direction may be equal to or less than the curvature radius of the outer edge.

The center part may include a pair of inclined surfaces formed to be inclined downward in a direction away from each other.

The center part may further include a center edge configured to connect the pair of inclined surfaces to each other and rounded upward.

The punching part may be further formed with a lower end of the bottom surface convexly rounded downward.

Advantageous Effects

According to the preferred embodiment of the present invention, it may be possible to minimize the void space that is not occupied by the electrode assembly while removing the bat-ear of the pouch-type secondary battery. Therefore, it may be possible to increase in energy density of the secondary battery.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be implemented in several different forms and is not limited or restricted by the following examples.

In order to clearly explain the present invention, detailed descriptions of portions that are irrelevant to the description or related known technologies that may unnecessarily obscure the gist of the present invention have been omitted, and in the present specification, reference symbols are added to components in each drawing. In this case, the same or similar reference numerals are assigned to the same or similar elements throughout the specification.

Also, terms or words used in this specification and claims should not be restrictively interpreted as ordinary meanings or dictionary-based meanings, but should be interpreted as meanings and concepts conforming to the scope of the present invention on the basis of the principle that an inventor can properly define the concept of a term to describe and explain his or her invention in the best ways.

FIG.2is a perspective view illustrating a state in which an electrode assembly is accommodated in the pouch-type battery case according to an embodiment of the present invention,FIG.3is a plan view illustrating a state in which the pouch-type battery case is unfolded according to an embodiment of the present invention, andFIG.4is a vertical cross-sectional view illustrating the state in which the pouch-type battery case is unfolded according to an embodiment of the present invention.

A pouch-type secondary battery (hereinafter, referred to as a ‘secondary battery’) according to the present invention may include a pouch-type battery case10(hereinafter, referred to as a ‘case’) and an electrode assembly20.

The electrode assembly20may be formed by alternately stacking electrodes and separators.

The electrode assembly20may be provided with an electrode tab21. The electrode tabs21are respectively connected to a positive electrode and a negative electrode of the electrode assembly20to protrude outward from the electrode assembly20, thereby providing a path, through which electrons are moved, between the inside and outside of the electrode assembly20.

The plurality of electrode tabs21connected to the positive electrode and the plurality of electrode tabs21connected to the negative electrode may protrude in different directions with respect to the electrode assembly20. However, the present invention is not limited thereto, and the plurality of electrode tabs21connected to the positive electrode and the plurality of electrode tabs21connected to the negative electrode may protrude in parallel in the same direction with respect to the electrode assembly20.

An electrode leads22supplying electricity to the outside of the secondary battery may be connected to the plurality of electrode tabs21by spot welding or the like. One end of the electrode lead22may be connected to the plurality of electrode tabs21, and the other end of the electrode lead22may protrude to the outside of the case10.

A portion of the electrode lead22may be surrounded by an insulating part23. For example, the insulating part23may include an insulating tape. The insulating part23may be disposed between a pair of terraces200of the case10, to be described later, and in this state, the pair of terraces200may be thermally fused to each other. In this case, a portion of the pair of terraces200may be thermally fused to the insulating part23. Thus, the insulating part23may prevent the electricity generated from the electrode assembly20from flowing to the battery case10through the electrode lead22and may maintain sealing of the battery case10.

The, the case10may accommodate the electrode assembly20.

In the present specification, the state in which the case10is unfolded refers to a state of the case10which is unfolded by releasing predetermined adhesion or sealing existing in the case10and then is left as it is without applying artificial force to the case10. Alternatively, the state may be referred to a state just before slowly unfolding the case10after releasing the predetermined adhesion or sealing existing in the case10, i.e., a state just before deforming the terrace200to be described later due to the unfolding operation.

That is, the ‘state in which the case10is unfolded’ may mean a state before the case10is manufactured by a forming process and then folded.

Hereinafter, the configuration of the case10will be described in detail based on the unfolded state of the case10.

The case10includes a pair of recess parts100, each of which has a recessed shape, a pair of terraces200disposed around the pair of recess parts100, and a bridge150disposed between the pair of recess parts100.

Each of the recess parts100may be an approximately cup shape. In more detail, each of the recess parts100may be recessed by a predetermined depth W (seeFIG.5) from the terrace200to be described later to form a recessed space S1.

A portion adjacent to a side210of the terrace200to be described later in the recessed space S1defined by the pair of recess parts100may form a void space that is not occupied by the electrode assembly20when the case10is sealed.

Preferably, recessed depths of the pair of recess parts100may be equal to each other. In this case, the pair of recess parts100may have a symmetrical shape.

However, the present invention is not limited thereto, and it is also possible that the recessed depths of the pair of recess parts100are different from each other. In this case, the pair of recess parts100may have an asymmetric shape.

Bottom surfaces101of the pair of recess parts100may be formed to be inclined downward in a direction toward each other. The bottom surfaces101of the pair of recess parts100may be connected to each other by the bridge150to be described later.

The bottom surface101and an inner circumference102a(seeFIG.8A) of each of the recess parts100may be connected to each other through an inner edge114, and an outer circumference of the recess part100and the terrace200, to be described later, may be connected to each other through an outer edge115. Each of the inner edge114and the outer edge115may be a curved surface rounded at a predetermined curvature radius.

The pair of terraces200may be disposed around the pair of recess parts100. The pair of terraces200may be formed to be inclined downward in a direction toward each other. In more detail, each of the terraces200may be formed in parallel to the bottom surface101of each of the recess parts100.

An angle θ formed by the pair of terraces200may be an obtuse angle. In more detail, the angle θ formed by the pair of terraces200may be 130 degrees to 170 degrees. Thus, there is an advantage that a bat-ear does not occur after the case10is sealed while minimizing the void space that is not occupied by the electrode assembly20after the case10is sealed.

If the angle θ is less than 130 degrees, the void space may increase, and if the angle θ is greater than 170 degrees, there is a risk that the bat-ear occurs, or excessive wrinkles are generated around a bending part300.

Also, the angle α between the terrace200and the circumferential surface102of the recess part100may be an obtuse angle.

Each of the terraces200may have an approximately ‘E’ shape. In more detail, each terrace200may include a side210, which is disposed at a side opposite to the bridge150with respect to the recess part100and extends parallel to the bridge150, and a pair of extension parts220extending from both ends of the side210in the inclined direction of the terrace200.

The pair of terraces200may be connected to each other by the bending part300. In more detail, the bending part300may connect lower ends of the extension part220to each other.

The bending part300may be formed to be rounded so as to be convex downward. Thus, the bending part300may be connected so that the lower ends of the terrace200are continuously connected without being bent.

Thus, the pair of terraces200may have an approximately ‘V’ shape together with the bending part300.

The bridge150may be disposed between the pair of recess parts100and connect the pair of recess parts100to each other. The bridge150may allow the recessed spaces S1of the pair of recess parts100to communicate with each other.

In more detail, the bridge150may include a pair of connection surfaces151formed to be inclined in a direction closer to each other upward from the bottom surface101of the pair of recess parts100, a first connection edge152connecting the pair of connection surfaces151to each other, and a pair of second connection edges153connecting the connection surface151to the bottom surface101of the recess part100.

The lower end of each of the connection surfaces151may be connected to the bottom surface101of the recess part100by the second connection edge153. Upper ends of the pair of connection surfaces151may be connected to each other by the first connection edge152.

In addition, each of the connection surfaces151may cover the recessed space S1of the recess part100at one side. In more detail, the recessed space S1may be defined by the bottom surface101and the circumferential surface102of the recess part100, and the connection surface151of the bridge150.

The first connection edge152may be formed to be rounded so as to be convex upward. Thus, the first connection edge152may be connected so that the upper ends of the pair of connection surfaces151are continuously connected without being bent.

Each of the second connection edges153may be formed to be rounded so as to be convex downward. Thus, each of the second connection edges153may be connected so that the bottom surface101of the recess part100and the lower end of the connection surface151are continuously connected without being bent.

Thus, the bottom surface101of each of the pair of recess parts100may have an approximately ‘W’ shape together with the bridge150.

FIG.5is an enlarged view illustrating the bridge and a periphery of the bridge, which are illustrated inFIG.4, andFIG.6is a view for explaining a detailed configuration of the pouch-type battery case illustrated inFIG.4.

The bending part300, the first connection edge152, the second connection edge153, the inner edge114, and the outer edge115may be formed as curved surfaces having predetermined curvature radii R1to R5, and it is preferable that each of the curvature radii R1to R5are constantly maintained.

However, the present invention is not limited thereto, and each of the curvature radii R1to R5may vary depending on the position thereof. In this case, the curvature radii R1to R5may mean average curvature radii of the bending part300, the first connection edge152, the second connection edge153, the inner edge114, and the outer edge115, respectively.

The inner edge114and the outer edge115may form a predetermined clearance CL in a horizontal direction. In more detail, the clearance CL may mean a horizontal distance between a boundary P2between the inner circumference102a(seeFIG.8A) of the recess part100and the inner edge114and a boundary P3between the outer circumference102bof the recess part100and the outer edge115.

The clearance CL may be less than or equal to the curvature radius R5of the outer edge115.

The clearance CL may be 0.5 mm or less, preferably 0.35 mm or less. In addition, the clearance CL may be equal to or greater than a thickness of the pouch sheet P, which is a base material of the case10. That is, the clearance CL may be equal to or greater than a thickness of the terrace200. For example, the clearance CL may be 0.15 mm or more.

Thus, while minimizing the void space that is not occupied by the electrode assembly20after the case10is sealed, it is possible to reduce a risk of cracks occurring during the forming process for forming the case10.

If the clearance CL is greater than 0.5 mm, the void space may increase excessively. Conversely, if the clearance CL is less than the thickness of the terrace200, the cracks may occur during the forming process for forming the case10.

Also, the curvature radius R4of the inner edge114may be greater than or equal to the curvature radius R5of the outer edge115.

As each of the curvature radii R4and R5of the inner edge114and the outer edge115increases, the void space that is not occupied by the electrode assembly20after the case10is sealed may be reduced. However, if each of the curvature radii R4and R5is excessively large, there is a limit to manufacturing the case10in a sharp shape, and the outer appearance of the secondary battery3is undesirable which deteriorates marketability. Thus, it is preferable to appropriately design the curvature radii R4and R5of the inner edge114desirable and the outer edge115.

A virtual line VL that passes through the boundary P3between the inner circumference102aof the recess part100and the inner edge114and is perpendicular to the terrace200may be defined. In this case, a distance from the virtual line VL to the connection surface151of the bridge150may be the first distance L1, and a distance from the virtual line VL to the bending part300of the terrace200may be a second distance L2with respect to the direction parallel to the terrace200.

The second distance L2may be less than the first distance L1. In more detail, a length L3from a center of the bending part300, i.e., from the lowermost end to the boundary P1between the terrace200and the bending part300may be less than each of the first distance L1and the second distance L2. That is, a difference between the first distance L1and the second distance L2may be greater than half a length of the bending part300.

Thus, when the case10is sealed after folding the lowermost end of the bending part300, the bat-ear may not occur in the case10.

In addition, a height of the lowermost end of the bending part300may be greater than or equal to a height of the uppermost end of the first connection edge152of the bridge150.

That is, the bending part300and the first connection edge152may have a predetermined height difference D in the vertical direction, or the lowermost end of the bending part300and the uppermost end of the first connection may be disposed on the same horizontal plane so that a height difference therebetween becomes zero. The height difference D may be referred to as a forming depth.

FIG.7is a cross-sectional view illustrating an apparatus for manufacturing the pouch-type battery case according to an embodiment of the present invention.

An apparatus for manufacturing the pouch-type battery case (hereinafter, referred to as a ‘manufacturing apparatus’) according to the present invention may include a die410, on which the pouch sheet P is seated, and a punch420punching the pouch sheet P from an upper side of the die410. The manufacturing apparatus may further include a stripper430that fixes the pouch sheet P at an upper side of the die410.

The pouch sheet P may be a base material of the case10. The pouch sheet P may be seated on the die410in an unfolded state or a partially folded state.

The stripper430may be disposed around the punch420. That is, at least a portion of the punch420may be accommodated in the stripper430, and an opening432penetrated vertically may be formed in the stripper430.

The stripper430may be configured to be elevatable independently of the punch420.

In addition, at least one of the die410or the punch420may be configured to be elevatable so that a distance therebetween varies.

For example, the die410may ascend in a state in which the pouch sheet P is seated, and the pouch sheet P may be fixed between the die410and the stripper430. In this state, as the die410further ascends together with the stripper430, the pouch sheet P may be punched by the punch420to form the case10described above.

For another example, the stripper430may descend before the punch420to fix the pouch sheet P in the state of being seated on the die410. In this state, the punch420may descend to punch the pouch sheet P, and thus, the case10described above may be formed.

Hereinafter, each of constituents of the manufacturing apparatus will be described in more detail.

The die410may include a pair of seating surfaces411inclined upward in a direction away from each other, a pair of forming parts412recessed or penetrated downward from the pair of seating surfaces411, and a center part413disposed between the pair of forming parts412.

The pair of seating surfaces411may constitute at least a portion of a top surface of the die410. Each of the seating surfaces411may be disposed around each of the forming part412. The pair of seating surfaces411may be formed to be inclined downward in a direction closer to each other.

An angle formed by the pair of seating surfaces411may be an obtuse angle and may correspond to the angle θ formed by the pair of terraces200of the case10. That is, the angle formed by the pair of seating surfaces411may be 130 degrees to 170 degrees and may be the same as or similar to the angle θ formed by the pair of terraces200.

Lower ends of the pair of seating surfaces411may be connected to each other in a downwardly convexly rounded curved surface shape, and the curved surface may have a shape and a curvature radius corresponding to the bending part300of the case10. In more detail, the curvature radius of the curved surface is the same as the curvature radius R1of the bending part300or the same as the sum of the curvature radius R1of the bending part300and the thickness of the pouch sheet P.

A pressing surface431constituting at least a portion of the bottom surface of the stripper430may be formed in parallel to the seating surface411of the die410. Thus, an edge portion of the pouch sheet P may be compressed between the pressing surface431of the stripper430and the seating surface411of the die410so as to be formed into the terrace200of the case10.

Each of the forming parts412of the die410may have a cup shape recessed downward from the seating surface411or a shape of an opening penetrated downward. In addition, a punching part421to be described later of the punch420may be inserted into the forming part412to punch the recess part100of the case10.

If the forming part412has the shape of the opening, air may be discharged through the opening during the punching operation of the punch420to improve moldability of the case10.

An upper end of the inner circumference of the forming part412and the seating surface411may be connected to each other by a die edge418.

The die edge418may have a shape and a curvature radius corresponding to the outer edge115of the case10. In more detail, the curvature radius of the die edge418may be the same as or similar to the curvature radius R5of the outer edge115. Thus, the outer edge115may be formed by the die edge418.

The center part413may be disposed between the pair of forming parts412. The center part413may have a shape corresponding to the bridge150of the case10.

In more detail, the center part413may include a pair of inclined surfaces414formed to be inclined upward in a direction closer to each other, and a center edge415connecting the pair of inclined surfaces414to each other.

Each of the inclined surfaces414may cover the inner space of the forming part412at one side. In more detail, the inner space of the forming part412may be defined by the inner circumference of the forming part412and the inclined surface414of the center part413.

The upper ends of the pair of inclined surfaces414may be connected to each other by the center edge415. The center edge415may be rounded to be convex upward. Thus, the center edge415may be connected so that the upper ends of the pair of inclined surfaces414are continuously connected without being bent.

The center edge415may have a shape and a curvature radius corresponding to the first connection edge152of the case10. In more detail, the curvature radius of the center edge415may be the same as or similar to the curvature radius R2of the first connection edge152.

A height of the uppermost end of the center edge415may be less than or equal to that of the lowermost end of the curved surface connecting the pair of seating surfaces411to each other.

The punch420may include a pair of punching parts421inserted into the pair of forming parts412of the die410.

The pair of punching parts421may be separated from each other so as to be spaced apart from each other. In this case, opposing surfaces423of the pair of punching parts421may face each other.

However, the present invention is not limited thereto, and a configuration in which the pair of punching parts421are connected to each other in a range in which the pair of punching parts do not interfere with the center part413of the die410may be provided.

Each of the punching parts421may have a shape corresponding to the recess part100of the case10. That is, bottom surfaces422of the pair of punching parts421may be formed to be inclined in a direction in which a height thereof decreases as the bottom surfaces422approach each other.

The bottom surfaces422of the pair of punching parts421may be inclined in a direction parallel to the seating surface411of the die410. That is, an angle formed by the bottom surfaces422of the pair of punching parts421may correspond to the angle θ formed by the pair of seating surfaces200of the case10.

That is, the angle formed by the bottom surfaces422of the pair of punching parts421may be an obtuse angle, more specifically, 130 degrees to 170 degrees.

A portion of the pouch sheet P may be pressed by the punching part421of the punch420, which is inserted into the forming part412of the die410, and may be formed into the recess part100of the case10.

The bottom surface422and a lower end of an outer circumference of the punching part421may be connected to each other by a punching edge427. The outer circumference of the punching part421may face the inner circumference of the stripper430.

The punching edge427may have a shape and a curvature radius corresponding to the inner edge114of the case10. In more detail, the curvature radius of the punching edge427may be the same as or similar to the curvature radius R4of the inner edge114. Thus, the inner edge114may be formed by the punching edge427.

Since the curvature radius R4of the inner edge114of the case10is equal to or greater than the curvature radius R5of the outer edge115, the curvature radius of the punching edge427may be equal to or greater than the curvature radius of the die edge418.

In addition, similarly to the horizontal clearance CL between the inner edge114and the outer edge115of the case10, a horizontal clearance between the punching edge427and the die edge418is 0.5 mm or less, preferably may be 0.35 mm or less.

In addition, since the horizontal clearance CL between the inner edge114and the outer edge115is less than or equal to the curvature radius R5of the outer edge115, the horizontal clearance between the punching edge427and the die edge418may be less than or equal to the curvature radius of the die edge418.

In addition, the bottom surface422of the punching part421and the lower end of the opposite surface423may be connected to each other by a side edge424. That is, the side edge424may be formed at a lower end of each of the bottom surfaces422.

The side edge424may have a downwardly convex rounded shape. The side edge424may have a shape and a curvature radius corresponding to the second connection edge153of the case10. In more detail, the curvature radius of the side edge424may be the same as or similar to the curvature radius R3of the second connection edge153.

Thus, a portion of the pouch sheet P may be formed into the bridge150of the case10by the center part413of the die410and the side edge424of the punch420.

FIGS.8aand8bare first experimental examples according to an embodiment of the present invention,FIGS.9aand9bare second experimental examples according to an embodiment of the present invention,FIGS.10aand10bare first comparative examples,FIGS.11aand11bare second comparative examples, andFIGS.12aand12bare third comparative examples.

In more detail,FIGS.8aand9aillustrate first and second experimental examples, in which the angle θ between the pair of terraces200of the case10is 140 degrees, and the clearance CL between the inner edge114and the outer edge115in the horizontal direction is formed to 0.35 mm and 0.5 mm, respectively. In the first and second experimental examples, an angle θ between the pair of terraces200of the case10is 140 degrees, the curvature radius R4of the inner edge114is 2.0 mm, and the curvature radius R5of the outer edge115is 1.5 mm.

FIG.10aillustrates the first comparative example in which the clearance CL between the inner edge114and the outer edge115in the horizontal direction is formed to 1 mm. That is, in the first comparative example, only the clearance CL increased when compared to the first and second experimental examples.

In the case of the first and second experimental examples, as illustrated inFIGS.8band9b, when one terrace200rotates to be horizontal, the clearances CL between the inner edge114and the outer edge115toward the one terrace200in the horizontal direction are measured to 1.09 mm and 1.25 mm, respectively. That is, when the case10according to the first and second experimental examples is folded and sealed to form the secondary battery, it is means that the clearances CL between the inner edge114and the outer edge115in the horizontal direction are measured to 1.09 mm and 1.25, respectively.

On the other hand, in the case of the first comparative example, as illustrated inFIG.10b, when one terrace200rotates to be horizontal, the clearance CL between the inner edge114and the outer edge115toward the one terrace200in the horizontal direction are measured to 1.78 mm. That is, when the case10according to the first comparative example is folded and sealed to form the secondary battery, it is means that the clearance CL between the inner edge114and the outer edge115in the horizontal direction are measured to 1.78 mm.

That is, as the clearance CL between the inner edge114and the outer edge115decreases, it is seen that the void space that is not occupied by the electrode assembly20is reduced.

FIG.11aillustrates second comparative example, in which the angle θ between the pair of terraces200of the case10is 120 degrees, and the clearance CL between the inner edge114and the outer edge115in the horizontal direction is formed to 0.5 mm. That is, the second comparative example, only the angle θ decreased when compared with the second experimental example.

In the case of the second comparative example, as illustrated inFIG.11b, when one terrace200rotates to be horizontal, the clearance CL between the inner edge114and the outer edge115toward the one terrace200in the horizontal direction are measured to 1.9 mm. That is, when the case10according to the second comparative example is folded and sealed to form the secondary battery, it is means that the clearance CL between the inner edge114and the outer edge115in the horizontal direction are measured to 1.9 mm.

That is, as the angle θ between the pair of terraces200increases, it is seen that the void space that is not occupied by the electrode assembly20decreases.

However, as described above, if the angle θ is too large, since there is a risk that a bat-ear occurs, or excessive wrinkles occur around the bending part300, it is preferable that the angle θ is 130 degrees to 170 degrees.

In the second comparative example illustrated inFIG.11a,FIG.12aillustrates a third comparative example, in which each of the curvature radius R4of the inner edge114and the curvature radius R5of the outer edge115is reduced to 1.0 mm.

In the case of the third comparative example, as illustrated inFIG.12b, when one terrace200rotates to be horizontal, the clearance CL between the inner edge114and the outer edge115toward the one terrace200in the horizontal direction are measured to 2.53 mm. That is, when the case10according to the third comparative example is folded and sealed to form the secondary battery, it is means that the clearance CL between the inner edge114and the outer edge115in the horizontal direction are measured to 2.53 mm.

That is, as each of the curvature radii R4and R5of the inner edge114and the outer edge115increase, it is seen that the void space that is not occupied by the electrode assembly20is reduced. However, as described above, if each of the curvature radii R4and R5is excessively large, there is a limit to manufacturing the case10in a sharp shape, and the outer appearance of the secondary battery3is undesirable which deteriorates marketability. Thus, it is preferable to appropriately design the curvature radii R4and R5of the inner edge114and the outer edge115.

FIG.13is a plan view illustrating the pouch-type secondary battery according to an embodiment of the present invention,FIG.14is an enlarged plan view illustrating an edge of a circumferential part and a periphery of the circumferential part, which are illustrated inFIG.13.

FIG.15is a perspective view illustrating the edge of the circumferential part and the periphery of the circumferential part, which are illustrated inFIG.13.

In a state in which the electrode assembly20(seeFIG.2) is disposed between the pair of recess parts100of the case10, the bending part300may be folded, and the pair of terraces200may be sealed to each other to form the secondary battery according to the embodiment of the present invention.

The secondary battery may include an accommodation part accommodating the electrode assembly20(seeFIG.2), a folding part forming a portion of a circumferential surface of the accommodation part, and a circumferential part expanded from the other portion of the circumferential surface of the accommodation part.

In more detail, the accommodation part is formed by the pair of recess parts100communicating with each other, and hereinafter, for convenience, the accommodation part is denoted by reference numeral ‘100’, which is the same reference numeral as that of the recess part10. In addition, the folding part is formed by folding the bridge150, and hereinafter, for convenience, the folding part is denoted by reference numeral ‘150’, which is the same reference numeral as that of the bridge150. In addition, the circumferential part is formed by attaching the pair of terraces200to each other, and hereinafter, for convenience, the circumferential part is denoted by reference numeral ‘200’, which is the same reference numeral as that of the terrace.

Therefore, for the secondary battery according to the embodiment of the present invention, the inner edge114(seeFIG.6) described above may be connected to an inner circumference of an inner top surface or an inner bottom surface of the accommodation part100. In addition, the outer edge115(seeFIG.6) may connect the outer circumference of the accommodation part100and the circumferential part200.

As described above, the curvature radius R4of the inner edge114may be equal to or greater than the curvature radius R5of the outer edge115, and the clearance CL between the inner edge114and the outer edge115in the horizontal direction may be less than the curvature radius R4of the inner edge114.

This may be confirmed by disassembling the secondary battery itself, but is not limited thereto, and may be confirmed by methods such as computerized tomography (CT), magnetic resonance imaging (MRI), X-ray, and the like. In this method, characteristics of the case10described above may be confirmed without disassembling the secondary battery.

The circumferential part200may include a long side portion formed by attaching the sides210of the pair of terraces200to each other and a short side portion formed by attaching the extension parts220of the pair of terraces200to each other. Hereinafter, the long side portion is denoted by reference numeral ‘210’, which is the same reference numeral as that of the side210, and the short side portion is denoted by reference numeral ‘220’, which is the same as that of the extension part220.

The long side portion210may extend in a longitudinal direction of the accommodation part100, and the short side portion220may extend in a width direction of the accommodation part100.

The circumferential part200may be sealed by thermal fusion. That is, the circumferential part200may be provided with a sealing part extending along the circumferential part.

In more detail, each of the short side portions220may include a sealing part221and a non-sealing part222.

The sealing part221may be formed to be elongated in a longitudinal direction of the short side portion220. A portion of the sealing part221may be formed by fusing a pair of extension parts220to each other, and the other portion of the sealing part221may be formed by fusing each of the extension part220to an insulating part23(seeFIG.2) surrounding an electrode lead22.

The non-sealing part222may be formed to be elongated in the longitudinal direction of the short side portion220and may be disposed inside the sealing part221. This is because, when the sealing part221is too close to the accommodation part100, the electrode tab21(seeFIG.2) of the electrode assembly20is damaged by a thermal fusion process.

That is, the non-sealing part222may be disposed between the sealing part221and the accommodation part100. The electrode tab21(seeFIG.2) of the electrode assembly20may be disposed on the non-sealing part222.

Thus, a folding part150side edge of the short side portion220may include an edge221aof the sealing part221and an edge222aof the non-sealing part222. The folding part150-side edge may mean an edge formed by folding the bending part300of the case10.

Hereinafter, for convenience of description, the edge of the non-sealing part222is called a first edge222a, and the edge of the sealing part221is called a second edge221a.

The first edge222amay be adjacent to the folding part150. The first edge222amay not be a straight line, but may be slightly curved or wrinkled, but is not limited thereto.

The second edge221amay extend in a direction opposite to the folding part150from the first edge222a. That is, the first edge222amay be disposed between the second edge221aand the folding part150.

The second edge221amay have a straight-line shape and may have a thickness less than that of the first edge222a. Also, the second edge221amay protrude more than the first edge222ain the width direction of the accommodation part100. This is because the first edge222ais the edge of the non-sealing part222, whereas the second edge221ais the edge of the sealing part221.

The first edge222aand the second edge221amay not protrude more than the folding part150in the width direction of the accommodation part100. That is, the first edge222aand the second edge221amay not protrude with respect to a virtual line VL2that is in contact with the folding part150and linearly extends in the longitudinal direction of the folding part150. Also, the second edge221amay be closer to the virtual line VL2than the first edge222a.

That is, in the secondary battery according to the related art, a portion corresponding to the second edge221aprotrudes from the folding part150to form the bat-ear. However, in the secondary battery according to the present invention, the bat-ear does not exist by the configuration of the case described above.

In addition, the folding part150-side edge of the short side portion220may further include a boundary part223connecting the first edge222ato the folding part150.

The boundary part223may be disposed between the first edge222aand the folding part150and may protrude more than the first edge222ain the width direction of the accommodation part100.

It is preferable that the boundary part223protrudes less than the folding part150in the width direction of the accommodation part100. In more detail, a degree of protrusion of the boundary part223may vary depending on a height difference D (seeFIG.6) between the bending part300and the first connection edge152described above, and it is desirable to be designed with an appropriate height difference.

FIG.16is a view illustrating a state in which a pouch-type battery case is unfolded according to another embodiment of the present invention.

Hereinafter, contents duplicated with the previously described contents will be cited, and described with a focus on the differences.

A circumferential surface of each of recess parts100may include an extension surface disposed at an opposite side of a bridge150and extending in a longitudinal direction of each of the recess parts100and a pair of side surfaces103extending in a width direction of the recess part100on both ends of the extension surface and connected to a connection surface151.

An area154on which the side surface103and the connection surface151of the bridge150are connected to each other may be formed as a curved surface having a predetermined curvature radius. Thus, it is possible to alleviate the occurrence of the creases around the connection part150when the case10is sealed.

The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present disclosure.

Thus, the embodiment of the present invention is to be considered illustrative, and not restrictive, and the technical spirit of the present invention is not limited to the foregoing embodiment.

Therefore, the scope of the present disclosure is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present disclosure.

DESCRIPTION OF THE SYMBOLS