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 be 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 general, in order to manufacture the secondary battery, first, electrode active material slurry is applied to a positive electrode collector and a negative electrode collector to manufacture a positive electrode and a negative electrode. Then, the electrodes are stacked on both sides of a separator to form an electrode assembly. Also, the electrode assembly is accommodated in a battery case, and then the battery case is sealed after an electrolyte is injected therein.

Such a secondary battery is classified into a pouch-type secondary battery and a can type secondary battery according to a material of a case accommodating the electrode assembly. In the pouch-type secondary battery, an electrode assembly is accommodated in a pouch made of a flexible polymer material. Also, in the can-type secondary battery, an electrode assembly is accommodated in a case made of a metal or plastic material.

In general, a pouch-type battery case is manufactured by performing press processing on a pouch film having flexibility to form a cup part. In addition, when the cup part is formed, an electrode assembly is accommodated in the cup part, and then, a side of the cup part is sealed to manufacture a secondary battery.

In the press processing, draw-molding is performed by inserting a pouch film into a molding device such as a press equipment and applying a pressure to the pouch film by using a punch to draw the pouch film. Hereinafter, this will be described in more detail.

<FIG> is a schematic view of a molding apparatus according to a related art.

A molding apparatus according to the related art include a die <NUM> in which a pouch film F is seated, and a molding space 2a is defined, a stripper <NUM> disposed above the die <NUM> to fix the pouch film F and having an opening 3a, a punch <NUM> that elongates the pouch film F through the opening 3a. In addition, when the die <NUM> and the stripper <NUM> ascend with respect to the punch <NUM>, or the punch <NUM> descends with respect to the die <NUM> and the stripper <NUM>, the punch <NUM> may apply a pressure to the pouch film F so that a portion of the pouch film F is elongated into the molding space 2a, and thus, a cup part <NUM> may be defined in the pouch film F.

However, in the molding apparatus according to the related art, to prevent the pouch film F from being pushed or damaged by frictional force in the process in which the punch <NUM> and the die <NUM> move relative to each other, a predetermined clearance g is required between an inner circumference of the punch <NUM> and an outer circumference of the molding space 2a. Thus, a circumferential surface <NUM> of the cup part <NUM>, which is defined in the pouch film F, may be inclined with respect to a bottom surface <NUM> of the cup part <NUM>. As a result, an empty space occupied by an electrode assembly (not shown) is generated in the cup part <NUM>, and thus, there is a problem in that energy density of the secondary battery is reduced.

In addition, in the molding apparatus according to the related art, when the punch <NUM> presses the pouch film F, stress is concentrated at a corner of the punch <NUM>. Thus, when the cup part <NUM> is deeply formed in the pouch film F, there is a problem in that a corner of the cup part <NUM> is excessively elongated, and thus, a remaining thickness becomes thin, and cracks or pin-holes occur at a corner of the cup part <NUM>.

In addition, there is a problem in that the circumferential surface <NUM> of the cup part <NUM>, which is defined by the molding apparatus according to the related art is not sufficiently elongated, and thus, compressive force acts to cause wrinkles due to buckling.

Documents <CIT>, <CIT>, <CIT> disclose molding apparatus according to the related art.

One object of the present invention for solving the above problems is to provide a molding apparatus and method, in which a remaining thickness of a corner of a cup part is maintained to be thick while molding the cup part having a sufficiently deep depth.

Another object of the prevent invention for solving the above problems is to provide a pouch-type battery case manufactured by the molding apparatus and method, and a secondary battery including the pouch-type battery case.

A molding apparatus according to an embodiment of the present invention may mold a cup part in a pouch film. The molding apparatus may include: a die on which the pouch film is seated on a top surface thereof and in which a first space recessed from the top surface is defined; a stripper which is disposed above the die to fix the pouch film and in which a second space is defined at a position corresponding to the first space; and a pressing part configured to apply a pneumatic or hydraulic pressure to the pouch film so that a portion of the pouch film is elongated into the first space.

The stripper may be provided with a cover part configured to seal the second space at an upper side, a passage through which the pressing part and the second space communicate with each other may be provided in the stripper or the cover part, and the pressing part may control an internal pressure of the second space by introducing or discharging a gas through the passage.

The molding apparatus may further include: a flexible bag disposed in the second space so as to be in contact with the pouch film; and a bag body which is configured to seal the second space, to which the flexible bag is connected, and in which a passage through which the pressing part and the flexible bag communicate with each other is provided. The pressing part may control an internal pressure of the flexible bag by introducing or discharging a fluid through the passage.

The molding apparatus further includes a first punch inserted into the first space and having a curved surface that is convex toward the pouch film.

The curved surface may have the highest central portion and a height that gradually decreases toward an inner circumference of the first space.

In the state in which the first punch is inserted into the first space, the central portion of the curved surface may be disposed at a height lower than that of a top surface of the die.

The first space may have a first width in a first direction and a second width in a second direction orthogonal to the first direction, and the curved surface may be a portion of an ellipsoid. <MAT> (where x is a coordinate in the first direction, y is a coordinate in the second direction, z is coordinates in a vertical direction, a is a half of the first width, b is a half of the second width, and c is a value obtained by multiplying an average value of the values a and b by a correction constant k of <NUM> to <NUM>).

The molding apparatus further includes a second punch inserted into the first space and having a plane facing the pouch film.

The pressing part may apply a higher pressure in a state in which the second punch is inserted into the first space when compared to a state in which the first punch is inserted into the first space.

A height difference between the plane and the top surface of the die when the second punch is inserted into the first space may be greater than a height difference between the curved surface and the top surface of the die when the first punch is inserted into the first space.

The molding apparatus may further include: a lower body which is disposed below the die and in which a third space communicating with the first space is defined; a flexible bag disposed in the third space and expanded into the first space so as to be in contact with the pouch film; a bag body which is configured to seal the third space and to which the flexible bag is connected; and a sub pressing part configured to control an internal pressure of the flexible bag by introducing or discharging a fluid through a passage provided in the bag body.

A molding method according to an embodiment of the present invention may mold a cup part in a pouch film. The molding method may include: a preparation process in which the pouch film is inserted between a die and a stripper; a fixing process in which the stripper fixes the pouch film; and a pressing process in which a pressing part applies a pneumatic or hydraulic pressure to the pouch film through a second space formed in the stripper so that a portion of the pouch film is elongated into a first space formed in the die.

The pressing process may include: a primary molding process in which a first punch having a curved top surface is inserted into the first space of the die, and a portion of the pouch film is in close contact with the curved surface, wherein the curved surface is convexly formed upward; and a secondary molding process in which a second punch having a planar top surface is inserted into the first space, and a portion of the pouch film is in close contact with the plane.

A pressure applied to the pouch film in the secondary molding process may be greater than that applied to the pouch film in the primary molding process.

A molding method according to an embodiment of the present invention may mold a cup part in a pouch film. The molding method may include: a preparation process in which the pouch film is inserted between a die and a stripper; a fixing process in which the stripper fixes the pouch film; and a pressing process of applying a pneumatic or hydraulic pressure to the pouch film so that a portion of the pouch film is elongated into a first space formed in the die to mold a cup part. The pressing process may include: a preliminary molding process in which a first flexible bag disposed in a second space formed in the stripper elongates the pouch film into the first space; a primary molding process in which a second flexible bag is expanded into the first space to press a portion of the pouch film so that a portion of the pouch film is formed is convexly formed upward; and a secondary molding process in which internal pressures of the first flexible bag and the second flexible bag are adjusted to be the same so that a portion of the pouch film is flatly formed.

In the primary molding process, the internal pressure of the second flexible bag may be greater than that of the first flexible bag.

The internal pressure of each of the first flexible bag and the second flexible bag in the secondary molding process may be greater than that of the second flexible bag in the primary molding process.

A pouch-type battery case according to an embodiment of the present invention may include: a cup part having a recessed shape; and a terrace disposed on at least a portion of a circumference of the cup part. The cup part may include: a bottom surface; a plurality of circumferential surfaces configured to connect the bottom surface to the terrace; and a corner on which a pair of circumferential surfaces, which are adjacent to each other, among the plurality of circumferential surfaces and the bottom surface meet each other. A thickness of the corner may be <NUM> times to <NUM> times a thickness of the bottom surface.

An angle defined by the circumferential surface with respect to the bottom surface or the terrace may be <NUM> degrees to <NUM> degrees.

The corner may have a curvature radius of <NUM> to <NUM>.

The cup part may further include: a first edge on which the circumferential surface and the terrace meet each other and which is rounded; and a second edge on which the bottom surface and the circumferential surface meet each other and which is rounded. A clearance between the first edge and the second edge may be <NUM> or less.

Each of the first edge and the second edge may have a curvature radius of <NUM> or more and less than <NUM>.

The cup part may further include: a first edge on which the bottom surface and the circumferential surface meet each other and which is rounded; and a second edge on which the circumferential surface and the terrace meet each other and which is rounded. A clearance between the first edge and the second edge may be less than a curvature radius of each of the first edge and the second edge.

A secondary battery according to an embodiment of the present invention may include: an electrode assembly; and a pouch-type battery case comprising a cup part having a recessed shape and a terrace disposed on at least a portion of a circumference of the cup part. The cup part may include: a bottom surface; a plurality of circumferential surfaces configured to connect the bottom surface to the terrace; and a corner on which a pair of circumferential surfaces, which are adjacent to each other, among the plurality of circumferential surfaces and the bottom surface meet each other. A thickness of the corner may be <NUM> times to <NUM> times a thickness of a central portion of the bottom surface.

According to the preferred embodiment of the present invention, since the pouch film is elongated by the pneumatic or hydraulic pressure to mold the cup part, the concentration of the stress to the corner of the cup part may be minimized. Thus, even if the cup part is molded deeply, the remaining thickness of the corner may be maintained to be thick, and the cracks or pin-holes may be prevented from occurring in the corner.

In addition, the circumferential surface of the cup part may be sufficiently elongated during the process of molding the cup part. Thus, the wrinkles due to the buckling may be prevented from occurring on the circumferential surface of the cup part.

In addition, the curvature radius of each of the edge and corner of the cup part may be minimized, and the circumferential portion of the cup part may be formed close to the vertical. Therefore, the outer appearance of the secondary battery may be sharp, and the energy density may be improved.

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

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.

<FIG> is a schematic view of a molding apparatus according to an embodiment of the present invention, and <FIG> is a bottom view of a die according to an embodiment of the present invention.

A molding apparatus according to an embodiment of the present invention includes a die <NUM> on which a pouch film F is seated on a top surface thereof, and a stripper <NUM> disposed above the die <NUM> to fix the pouch film F, and a pressing part <NUM> applying a pneumatic or hydraulic pressure to the pouch film F. The molding apparatus may further include a first punch <NUM> and a second punch <NUM>, which are inserted into a first space S1.

The pouch film F may have a predetermined thickness t. The pouch film F may be a laminate sheet in which a pair of resin layers disposed at both the outermost surfaces and a metal layer disposed between the pair of resin layers are laminated.

The pouch film F may be seated on the top surface of the die <NUM>. The first space S1 recessed downward from the top surface may be defined in the die <NUM>. The first space S1 may be opened to upper and lower sides. When the pouch film F is seated on the top surface of the die <NUM>, the pouch film F may cover the first space S1 from the upper side. In addition, the first punch <NUM> and the second punch <NUM> to be described later may be inserted into the first space S1 from the lower side of the die <NUM>.

A cross-section of the first space S1 of the die <NUM> may have a substantially rectangular shape. In more detail, the first space S1 may have a first width W1 in a first direction and a second width W2 in a second direction orthogonal to the first direction. That is, the first direction may be parallel to a horizontal direction of the first space S1, and the second direction may be parallel to a vertical direction of the first space S1. In addition, the first width W1 may be a horizontal width of the first space S1, and the second width W2 may be a vertical width of the first space S1.

The stripper <NUM> may face the die <NUM> with the pouch film F interposed therebetween. The stripper <NUM> may be configured to be elevated with respect to the die <NUM>. The pouch film F may be inserted between the die <NUM> and the stripper <NUM> in a state in which the stripper <NUM> ascends, and then, when the stripper <NUM> descends, the pouch film F may be fixed between the die <NUM> and the stripper <NUM>.

A second space S2 may be defined in the stripper <NUM>. The second space S2 may be defined at a position corresponding to the first space S1 of the die <NUM>.

In this embodiment, the second space S2 may be closed to the upper side and opened to the lower side. In more detail, the stripper <NUM> may be provided with a cover part <NUM> that sealing the second space S2 from the upper side. The cover part <NUM> may be coupled to the stripper <NUM> as a configuration separate from the stripper <NUM> or may be provided to be integrated with the stripper <NUM>.

A passage 21a may be defined in the cover part <NUM> to allow the pressing part <NUM> to be described later to communicate with the second space S2. However, the present invention is not limited thereto, and the passage 21a may be provided in the stripper <NUM>.

When the stripper <NUM> fixes the pouch film F, the pouch film F may cover the second space S1 from the lower side. That is, in the state in which the pouch film F is fixed between the die <NUM> and the stripper <NUM>, a portion of the pouch film F may be disposed between the first space S1 and the second space S2. Hereinafter, the portion of the pouch film F disposed between the first space S1 and the second space S2 is referred to as a target area <NUM>.

The pressing part <NUM> may apply the pneumatic or hydraulic pressure to the pouch film F, more specifically, to the target area <NUM> through the second space S2. As a result, the target area <NUM> may be elongated into the first space S1, and the target area <NUM> may be molded into the cup part. Thus, the cup part is indicated by the same reference numeral '<NUM>' as the target area <NUM>.

Since the target area <NUM> of the pouch film F is elongated into the first space S1 and molded into the cup part <NUM>, the horizontal length of the cup part <NUM> may be the same as or similar to the first width W1 of the first space S1, and the vertical length of the cup part <NUM> may be the same as or similar to the second width W2 of the first space S1.

The configuration of the pressing part <NUM> is not limited. In this embodiment, the pressing part <NUM> may apply the pneumatic pressure to the target area <NUM>. For example, the pressing part <NUM> may include a pneumatic pump.

In more detail, the pressing part <NUM> may control an internal pressure of the second space S2 by introducing a gas into and out of the second space S2 through the passage 21a. Thus, when the internal pressure of the second space S2 is higher than the internal pressure (e.g., atmospheric pressure) of the first space S1, the target area <NUM> may be elongated into the first space S1 by a pressure difference between the first space S1 and the second space S2.

That is, since an isostatic pressure is applied to the target area <NUM>, a thickness t of the target area <NUM> may be uniformly reduced as a whole in the process of elongating the target area <NUM>. Thus, the concentration of the stress to a local area on the target area <NUM> may be minimized.

The first punch <NUM> and the second punch <NUM> may be inserted into the first space S1 from the lower side of the die <NUM>. In more detail, the first punch <NUM> and the second punch <NUM> may be alternatively inserted into the first space S1.

For example, the first punch <NUM> and the second punch <NUM> may move horizontally with respect to the die <NUM>, and the die <NUM> may move vertically with respect to the first punch <NUM> and the second punch <NUM>. In this case, when the die <NUM> descends in a state in which the first punch <NUM> is aligned to be disposed at the lower side of the first space S1, the first punch <NUM> may be inserted into the first space S1. In addition, when the die <NUM> descends in a state in which the second punch <NUM> is aligned to be disposed at the lower side of the first space S1, the second punch <NUM> may be inserted into the first space S1.

However, the present invention is not limited thereto, and the die <NUM> may move horizontally with respect to the first punch <NUM> and the second punch <NUM>, or the first punch <NUM> and the second punch <NUM> may be elevated with respect to the die <NUM>.

An outer circumference of each of the punches <NUM> and <NUM> may be in contact with or adjacent to the inner circumference of the first space S1 of the die <NUM>. This is because the pouch film F is not inserted between the outer circumference of each of the punches <NUM> and <NUM> and the inner circumference of the first space S1.

The first punch <NUM> may have a curved surface <NUM> that is convexly defined toward the pouch film F, more specifically, the target area <NUM>. That is, the curved surface <NUM> may define a top surface of the first punch <NUM>. The curved surface <NUM> may have the highest central portion and has a height that gradually decreases toward the inner circumference of the first space S1. In more detail, the curved surface <NUM> may have a shape corresponding to a portion of an ellipsoid.

In the state in which the first punch <NUM> is inserted into the first space S1, the target area <NUM> may be pressed by the pressing part <NUM> so as to be in close contact with the curved surface <NUM> of the first punch <NUM>.

The second punch <NUM> may be inserted into the first space S1 after the first punch <NUM> is separated from the first space S1.

The second punch <NUM> may have a plane <NUM> facing the pouch film F, more specifically, the target area <NUM>. That is, the plane <NUM> may define a top surface of the second punch <NUM>.

In the state in which the second punch <NUM> is inserted into the first space S1 of the die <NUM>, the target area <NUM> may be pressed by the pressing part <NUM> so as to be in close contact with the plane <NUM> of the second punch <NUM>.

<FIG> is a flowchart illustrating a molding method performed using the molding apparatus according to an embodiment of the present invention, and <FIG> are views for explaining an operation of the molding apparatus according to an embodiment of the present invention.

A molding method according to this embodiment may include a preparation process (S10) in which a pouch film F is inserted between a die <NUM> and a stripper <NUM>, a fixing process (S20) in which the stripper <NUM> fixes the pouch film F, and a pressing process (S30) of applying a pneumatic or hydraulic pressure to the pouch film F.

In the preparation process (S10), the stripper <NUM> may ascend by a predetermined height with respect to the die <NUM>, and the pouch film F may be inserted between the die <NUM> and the stripper <NUM>. Thus, the pouch film F may be seated on a top surface of the die <NUM>.

During the fixing process (S20), the stripper <NUM> may descend toward the die <NUM>, and the pouch film F may be fixed between the die <NUM> and the stripper <NUM>. Here, the target area <NUM> of the pouch film F may be disposed between the first space S1 of the die <NUM> and the second space S2 of the stripper <NUM>.

During the pressing process (S30), the pressing part <NUM> may apply the pneumatic or hydraulic pressure to the pouch film F through the second space S2 of the stripper <NUM>.

In this embodiment, the pressing part <NUM> may apply the pneumatic pressure to the target area <NUM>. The pressing part <NUM> may allow the second space S2 to increase in internal pressure through the passage 21a, thereby applying an isotropic pressure to the pouch film F, more specifically, to the target area <NUM>. Thus, the target area <NUM> may be elongated into the first space S1 and then be molded into the cup part <NUM>.

In more detail, the pressing process (S30) may include a preliminary molding process (S31), a primary molding process (S32), and a secondary molding process (S33).

Referring to <FIG>, during the preliminary molding process (S31), the pressing part <NUM> may press the target area <NUM> in a state in which the first space S1 is opened. Here, the pressure applied to the target area <NUM> by the pressing part <NUM> may be appropriately adjusted so that a remaining thickness of the target area <NUM> is not excessively thin.

In more detail, the remaining thickness of the elongated target area <NUM> in the preliminary molding process S31 may be about <NUM>% of the thickness t of the pouch film F. That is, the thickness of the target area <NUM> may decrease by approximately <NUM>%, and the area of the target area <NUM> may increase by approximately <NUM>%.

As described above, since the isotropic pressure is applied to the target area <NUM>, the target area <NUM> may be uniformly elongated into the first space S1 to form a predetermined curved surface. The curved surface of the target area <NUM> may be formed to have the lowest central portion and have a height that gradually increases toward the inner circumference of the first space S1.

In more detail, the curved surface formed by the target area <NUM> may form a portion of an ellipsoid defined by Equation <NUM> below.

In Equation <NUM>, x is a coordinate in a first direction parallel to the horizontal direction of the first space S1, y is a coordinate in a second direction parallel to the vertical direction of the first space S1, and z is coordinates in the vertical direction. In addition, a is a half of a first width W1, b is a half of a second width W2, and c1 is a depth of the curved surface formed by the target area <NUM>.

The c1 may be proportional to an average value of the values a and b. For example, when the thickness of the target area <NUM> is elongated to decrease by about <NUM>%, the c1 may be approximately <NUM> times the average value of the values a and b. Thus, those skilled in the art will readily understand that the c1 easily increases as a ratio of the values a and b approaches <NUM> if a value obtained by multiplying the values a and b is constant, and the remaining thickness of the target area <NUM> is constant.

Referring to <FIG>, during the primary molding process (S32), the first punch <NUM> may be inserted into the first space S1 of the die <NUM>. Here, the pressing part <NUM> may continuously maintain the pressure applied to the target area <NUM>.

In the state in which the first punch <NUM> is inserted into the first space S1, the central portion of the curved surface <NUM> of the first punch <NUM> may be disposed at a height lower than the top surface of the die <NUM>. In more detail, the first punch <NUM> may be inserted into the first space S1 at a height that does not interfere with the elongated target area <NUM> in the preliminary molding process S31.

The curved surface <NUM> of the first punch <NUM> may have an approximately symmetrical shape with respect to the curved surface formed by the elongated target area <NUM> in the preliminary molding process (S31). That is, the curved surface <NUM> of the first punch <NUM> may form a portion of an ellipsoid defined by Equation <NUM> below.

In Equation <NUM>, x is a coordinate in a first direction parallel to the horizontal direction of the first space S1, y is a coordinate in a second direction parallel to the vertical direction of the first space S1, and z is coordinates in the vertical direction. In addition, a is a half of the first width W1, b is a half of the second width W2, and c2 is a value obtained by multiplying the average value of the values a and b by a predetermined correction constant k.

As described in Equation <NUM> above, when the thickness of the target area <NUM> is elongated to decrease by about <NUM>% in the preliminary molding process (S31), c1 may be approximately <NUM> times the average value of a and b.

Thus, the correction constant k may be determined within a predetermined range with a median value of <NUM> so that the c2 corresponds to the c1. In more detail, the correction constant k may be <NUM> to <NUM>, and may be appropriately determined according to a depth of the cup part <NUM> to be molded.

Due to the shape of the curved surface <NUM> of the first punch <NUM>, a portion of the target area <NUM> may be in close contact with the curved surface <NUM> during the primary molding process (S32), and the other portion of the target area 110may be in contact with or adjacent to the inner circumference of first space S1. Hereinafter, the portion of the target area <NUM> will be referred to as a first area <NUM>, and the other portion of the target area <NUM> will be referred to as a second area <NUM>.

Thereafter, the first area <NUM> may be molded as a bottom surface of the cup part <NUM>, and the second area <NUM> may be molded as the circumferential surface of the cup part <NUM>. Thus, the bottom surface of the cup part <NUM> is denoted by the same reference numeral '<NUM>' as that of the first area <NUM>, and the circumferential surface of the cup part <NUM> is denoted by the same reference numeral '<NUM>' as the second area <NUM>.

Since the first area and the second area <NUM> are formed to be previously divided into each other in the primary molding process (S32), the second area <NUM> may be easily elongated in the subsequent secondary molding process (S33). Thus, there is an advantage that the cup part <NUM> is deeply molded without wrinkles due to buckling on the circumferential surface <NUM> of the cup part <NUM>.

In addition, since a portion at which the first area <NUM> and the second area <NUM> meet each other forms an acute angle, in the subsequent secondary molding process (S33), the second area <NUM> may be in easily close contact with the inner circumference of the first space S1. Thus, the circumferential surface <NUM> of the cup part <NUM> may be formed to be perpendicular to the bottom surface <NUM>, and a curvature radius of each of an edge and corner of the cup part <NUM> may be minimized to prevent stress from being concentrated to the corner of the cup part <NUM>.

Referring to <FIG>, the second punch <NUM> may be inserted into the first space S1 of the die <NUM> during the secondary molding process S33. In more detail, when the primary molding process (S32) is completed, the first punch <NUM> may be separated from the first space S1 of the die <NUM>, and the second punch <NUM> may be inserted into the first space S1 of the die <NUM> so that the secondary molding process (S33) is performed.

In the state in which the second punch <NUM> is inserted into the first space S1, a plane <NUM> of the second punch <NUM> may be disposed at a height lower than the top surface of the die <NUM>.

In more detail, the second punch <NUM> may be inserted into the first space S1 at a height lower than that of the first punch <NUM> during the primary molding process (S32). That is, a height difference h2 between the plane <NUM> and the top surface of the die <NUM> when the second punch <NUM> is inserted into the first space S1 may be greater than a height difference h1 between the curved surface <NUM> and the top surface of the die <NUM> when the first punch <NUM> is inserted into the first space S1.

In addition, the pressure applied to the pouch film F, more specifically, the target area <NUM> in the secondary molding process (S33) may be higher than that in the primary molding process (S32). That is, the pressing part <NUM> may apply a higher pressure in a state in which the second punch <NUM> is inserted when compared to a state in which the first punch <NUM> is inserted into the first space S1.

Thus, during the secondary molding process (S33), the first area <NUM> may be in close contact with the plane <NUM> of the second punch <NUM>, and the second area <NUM> may be in close contact with the inner circumference of the first space S1. Thus, the molding of the cup part <NUM> may be completed.

In more detail, the first area <NUM> may be horizontally formed as the bottom surface <NUM> of the cup part <NUM>, and the second area <NUM> may be vertically formed as the circumferential surface <NUM> of the cup part <NUM>. In addition, during the secondary molding process (S33), since the second area <NUM> is elongated downward, the depth of the cup part <NUM> may be sufficiently deep.

The primary molding process (S32) may be directly performed without the pressing process (S30) including the preliminary molding process (S31). In this case, the pressing part <NUM> may start the pressing on the target area <NUM> in the state in which the first punch <NUM> is inserted into the first space S1 of the die <NUM>.

<FIG> is an exploded perspective view illustrating the secondary battery according to an embodiment of the present invention.

The secondary battery <NUM> according to the present invention may include a pouch-type battery case <NUM> (hereinafter, referred to as a 'battery case') and an electrode assembly <NUM> accommodated in the battery case <NUM>.

The battery case <NUM> may be molded by the molding apparatus and molding method described above. The battery case <NUM> may include a cup part <NUM> having a recessed shape and a terrace <NUM> disposed at least a portion of a circumference of the cup part <NUM>. The terrace <NUM> may be a portion of the pouch film F in which the cup part <NUM> is not formed.

In more detail, the battery case <NUM> may be provided by sealing a pair of cases <NUM> and <NUM> connected to each other through a folding part <NUM>. However, the present invention is not limited thereto, and the pair of cases <NUM> and <NUM> may be sealed in a state of being separated from each other to provide the battery case <NUM>.

In addition, at least one of the pair of cases <NUM> and <NUM> may be provided with the cup part <NUM> having the recessed shape. The cup part <NUM> may be recessed by a predetermined depth from the terrace <NUM> to define a space in which the electrode assembly <NUM> is accommodated. Hereinafter, a case in which the pair of cases <NUM> and <NUM> includes a first case <NUM>, in which the cup part <NUM> is provided, and a second case <NUM>, in which the cup part <NUM> is not provided, will be described as an example.

The first case <NUM> may include the terrace <NUM> disposed at least a portion of the circumference of the cup part <NUM>. In more detail, the terrace <NUM> may be connected to an upper end of the circumferential surface <NUM> of the cup part <NUM>.

In the state in which the electrode assembly <NUM> is accommodated in the cup part <NUM>, the folding part <NUM> may be folded so that the second case <NUM> covers the cup part <NUM>. In addition, the secondary battery <NUM> may be provided by fusing edge portions of the terrace <NUM> and the second case <NUM> to provide the sealing portion <NUM> (see <FIG>), thereby manufacturing the secondary battery <NUM>.

The electrode assembly <NUM> may include a plurality of electrodes <NUM> (see <FIG>) and a plurality of separators <NUM> that are alternately stacked. The plurality of electrodes <NUM> are alternately stacked with the separator <NUM> interposed therebetween and may include a positive electrode and a negative electrode, which have opposite polarities.

In addition, the electrode assembly <NUM> may include a plurality of electrode tabs <NUM> welded to each other. The plurality of electrode tabs <NUM> may be connected to the plurality of electrodes <NUM> and protrude from the electrode assembly <NUM> to the outside to serve as a passage through which electrons move between the inside and the outside of the electrode assembly <NUM>. The plurality of electrode tabs <NUM> may be disposed inside the battery case <NUM>.

The electrode tab <NUM> connected to the positive electrode and the electrode tab <NUM> connected to the negative electrode may protrude in different directions with respect to the electrode assembly <NUM>. However, the present invention is not limited thereto, and the electrode tab <NUM> connected to the positive electrode and the electrode tab <NUM> connected to the negative electrode may protrude in the same direction in parallel with each other.

A lead <NUM> supplying electricity to the outside of the secondary battery may be connected to the plurality of electrode tabs <NUM> by spot welding or the like. The lead <NUM> may have one end connected to the plurality of electrode tabs <NUM> and the other end protruding to the outside of the battery case <NUM>.

A portion of the lead <NUM> may be surrounded by an insulating part <NUM>. For example, the insulating part <NUM> may include an insulating tape. The insulating part <NUM> may be disposed between the terrace <NUM> and the second case <NUM> of the first case <NUM>, and in this state, the terrace <NUM> and the second case <NUM> may be thermally fused to each other. In this case, a portion of each of the terrace <NUM> and the second case <NUM> may be thermally fused to the insulating part <NUM>. Thus, the insulating part <NUM> may prevent the electricity generated from the electrode assembly <NUM> from flowing to the battery case <NUM> through the lead <NUM> and may maintain sealing of the battery case <NUM>.

<FIG> is an enlarged view of a portion 'A' of <FIG>, <FIG> is a cross-sectional view illustrating the inside of the secondary battery according to an embodiment of the present invention, and <FIG> is an enlarged view of a portion 'B' of <FIG>.

Hereinafter, the configuration of the cup part <NUM> of the battery case <NUM> will be described in detail.

The cup part <NUM> may include a bottom surface <NUM> and a circumferential surface <NUM>. The circumferential surface <NUM> may connect the bottom surface <NUM> to the terrace <NUM>. The circumferential surface <NUM> may be provided in plurality, in more detail, in four.

The bottom surface <NUM> may cover one surface of the electrode assembly <NUM>, and the circumferential surface <NUM> may surround the electrode assembly <NUM>.

In addition, the cup part <NUM> may include a first edge <NUM> on which the circumferential surface <NUM> and the terrace <NUM> meet each other, a second edge <NUM> on which the bottom surface <NUM> and the circumferential surface <NUM> meet each other, and a third edge <NUM> on which a pair of circumferential surfaces, which are adjacent to each other, among the plurality of circumferential surfaces <NUM> meet each other. Each of the edges <NUM>, <NUM>, <NUM> may be rounded to have a predetermined curvature radius.

In addition, the cup part <NUM> may include a corner <NUM> on which a pair of adjacent circumferential surfaces <NUM> of the plurality of circumferential surfaces <NUM> and a bottom surface <NUM> meet each other. That is, the corner <NUM> may be a portion at which a pair of second edge <NUM> and third edge <NUM>, which are adjacent to each other, overlap each other. The corner <NUM> may have a predetermined curvature radius.

Since the cup part <NUM> has four circumferential surfaces <NUM>, each of the edges <NUM>, <NUM>, and <NUM> and the corner <NUM> may be provided in four.

In the molding apparatus and molding method according to an embodiment of the present invention, concentration of stress to each of the edge <NUM>, <NUM>, <NUM> and the corner <NUM> of the cup part <NUM> may be minimized. Thus, the curvature radius of each of the edges <NUM>, <NUM>, <NUM> and the corner <NUM> may be sufficiently small, and simultaneously, a remaining thickness of the corner <NUM> may be sufficiently thick.

In more detail, at least a portion of the plurality of edges <NUM>, <NUM>, and <NUM> may have a curvature radius of <NUM> or more and less than <NUM>. A curvature radius R1 of the first edge <NUM> may be a curvature radius with respect to an outer surface of the first edge <NUM>. A curvature radius R2 of the second edge <NUM> may be a curvature radius with respect to an inner surface of the second edge <NUM>.

In addition, the corner <NUM> may have a curvature radius in a range of <NUM> to <NUM>. The curvature radius of the corner <NUM> may be a curvature radius with respect to an inner surface of the corner <NUM>.

On the other hand, since the cup part according to the related art is molded by the direct pressing of the punch, the elongation may be concentrated on each of the edge and corner of the cup part, and thus, each of the edges may have a curvature radius of <NUM> to <NUM>, and the corner may have a curvature radius of <NUM> to <NUM> to prevent cracks and like from occurring in each of the edge and the corner. This is a fact well known to those skilled in the art. Therefore, it is seen that the curvature radius of each of the edge <NUM>, <NUM>, <NUM> and the corner <NUM> of the cup part <NUM> according to an embodiment of the present invention is less compared to the cup part according to the related art.

Since the curvature radius of each of the edges <NUM>, <NUM>, <NUM> and the corner <NUM> is sufficiently small, an outer appearance of the cup part <NUM> may be sharply provided. Also, even if the electrode <NUM> of the electrode assembly <NUM> is disposed to be very adjacent to the circumferential surface <NUM> of the cup part <NUM>, an interference between the electrode <NUM> and the cup part <NUM> may be prevented from occurring.

That is, since the electrode <NUM> of the electrode assembly <NUM> is disposed to be very adjacent to the circumferential surface <NUM> of the cup part <NUM>, an empty space in the cup part <NUM> may be reduced, and energy density of the secondary battery may increase to prevent the electrode assembly <NUM> from moving inside the cup part <NUM>. In this case, the edge portion 220a of the separator <NUM> protruding further outward than the electrode <NUM> may be folded to be internal contact with the circumferential surface <NUM> of the cup part <NUM>. The edge portion 220a of the separator <NUM> may be randomly folded or folded in a predetermined direction. For example, the edge portion 220a of the separator <NUM> may be folded toward an opposite direction of the bottom surface <NUM>.

In addition, a thickness of the corner <NUM> may be <NUM> times to <NUM> times a thickness of the bottom surface <NUM>. That is, the thickness of the corner <NUM> may be less <NUM>% to <NUM>% than the thickness of the bottom surface <NUM>. In this case, the thickness of the bottom surface <NUM> may be a thickness measured at a center of the bottom surface <NUM>, and the thickness of the corner <NUM> may be a thickness measured at a center of the corner <NUM>.

On the other hand, since the cup part according to the related art is molded by the direct pressing of the punch, the elongation may be concentrated at the corner of the cup part, and thus the thickness of the corner of the cup part may be less <NUM>% to <NUM>% than the thickness of the bottom surface of the cup part. This is a fact well known to those skilled in the art. Therefore, when compared to the cup part according to the related art, it is confirmed that the remaining thickness of the corner <NUM> of the cup part <NUM> according to the embodiment of the present invention is thick.

Since the remaining thickness of the corner <NUM> is sufficiently thick, cracks or pin-holes may not occur in the corner <NUM>. In addition, the cup part <NUM> may be provided to be deeper.

In the molding apparatus and the molding method according to an embodiment of the present invention, the circumferential surface <NUM> of the cup part <NUM> may be disposed close to perpendicular to the bottom surface <NUM>. In more detail, an angle defined by the circumferential surface <NUM> of the cup part <NUM> with respect to the bottom surface <NUM> or the terrace <NUM> of the cup part <NUM> may be <NUM> degrees to <NUM> degrees.

Thus, a clearance CL between the first edge <NUM> and the second edge <NUM> may be minimized. In this case, the clearance CL may mean a distance between a virtual first vertical line V1 that vertically passes through a boundary point P1 between the first edge <NUM> and the circumferential surface <NUM> and a virtual second vertical line V2 that vertically passes through a boundary point P2 between the second edge <NUM> and the circumferential surface <NUM>.

In more detail, the clearance CL between the first edge <NUM> and the second edge <NUM> may be <NUM> or less. When the circumferential surface <NUM> of the cup part <NUM> is completely vertical, the clearance CL may be zero.

In addition, the clearance CL between the first edge <NUM> and the second edge <NUM> may be less than or equal to each of the curvature radius R1 of the first edge <NUM> and the curvature radius R2 of the second edge <NUM>.

Thus, since the empty space in the cup part <NUM> is further reduced, the energy density of the secondary battery may be improved, and the outer appearance of the secondary battery may be further improved.

<FIG> is a schematic view of a molding apparatus according to another embodiment of the present invention.

Hereinafter, the same content as that of the molding apparatus according to the embodiment described above will be referred to and described with a focus on the differences.

A molding apparatus according to this embodiment may further include a flexible bag <NUM> and a bag body <NUM>.

The flexible bag <NUM> may be disposed in a second space S2 (see <FIG>) of a stripper <NUM>. The flexible bag <NUM> may be in contact with a pouch film F, more specifically, a target area <NUM>. The flexible bag <NUM> may expand by a pressing part <NUM> to apply a pressure to the target area <NUM>, and the target area <NUM> may be elongated into a first space S1.

The bag body <NUM> may be connected to the flexible bag <NUM>. The bag body <NUM> may seal an inner space of the flexible bag <NUM>. That is, the inner space of the flexible bag <NUM> may be defined by the flexible bag <NUM> and the bag body <NUM>.

In addition, the bag body <NUM> may seal the second space S2 of the stripper <NUM>. In more detail, the second space S2 of the stripper <NUM> according to this embodiment may be opened to an upper side. In addition, the bag body <NUM> may cover the second space S2 from the upper side in the state in which the flexible bag <NUM> is inserted into the second space S2. That is, the bag body <NUM> may serve as the cover part <NUM> (see <FIG>) described in the foregoing embodiment.

In addition, in the bag body <NUM>, a passage 24a through which a pressing part <NUM> and an inner space of the flexible bag <NUM> communicate with each other may be provided.

The pressing part <NUM> according to this embodiment may control an internal pressure of the flexible bag <NUM> by introducing a fluid through the passage 24a. The term "fluid" encompasses a liquid and a gas. That is, the pressing part <NUM> may apply a pneumatic or hydraulic pressure to the target area <NUM>. For example, the pressing part <NUM> may include a pneumatic pump or a hydraulic pump.

Thus, when the internal pressure of the flexible bag <NUM> is higher than the internal pressure (e.g., atmospheric pressure) of the first space S1, the target area <NUM> may be elongated into the first space S1 by a pressure difference between the first space S1 and the flexible bag <NUM>.

Particularly, when the pressing part <NUM> applies the hydraulic pressure to a pouch film F using a liquid, the liquid may not be in contact with the stripper <NUM> and the pouch film F by the flexible bag <NUM>. As a result, possibility that the molding apparatus is broken or malfunctioned due to the liquid may be removed.

Those skilled in the art may easily understand that the molding method according to the above-described embodiment is carried out even by the molding apparatus according to another embodiment of the present invention, and the cup part <NUM> of the battery case <NUM> may be molded.

<FIG> is a schematic view of a molding apparatus according to further another embodiment of the present invention.

A molding apparatus according to another embodiment of the present invention does not include a first punch <NUM> and a second punch <NUM>, but uses a pneumatic or hydraulic pressure at both sides of a pouch film F to mold a cup part <NUM>.

Hereinafter, a case in which a pressing part <NUM> applies the hydraulic pressure to a pouch film F as in the other embodiments described above will be described as an example. In addition, for convenience of description, a flexible bag <NUM> is referred to as a 'first flexible bag', and a bag body <NUM> is referred to as a 'first bag body'. However, the present invention is not limited thereto, and it is of course also possible for the pressing part <NUM> to apply the pneumatic pressure to the pouch film F as in the above-described exemplary embodiment.

The molding apparatus according to another embodiment of the present invention may further include a lower body <NUM>, a second flexible bag <NUM>, a second bag body <NUM>, and a sub pressing part <NUM>.

The lower body <NUM> may be disposed below a die <NUM>. A third space S3 communicating with a first space S1 of the die <NUM> may be defined in the lower body <NUM>. The lower body <NUM> may be manufactured to be separated from the die <NUM>. However, the present invention is not limited thereto, and the lower body <NUM> and the die <NUM> may be integrated with each other.

The second flexible bag <NUM> may be disposed in a third space S3 and be expanded into the first space S1 so as to be in contact with the pouch film F.

The second bag body <NUM> may be connected to the second flexible bag <NUM>. The second bag body <NUM> may seal an inner space of the second flexible bag <NUM>. That is, the inner space of the second flexible bag <NUM> may be defined by the second flexible bag <NUM> and the second bag body <NUM>.

In addition, the second bag body <NUM> may seal the third space S3 of the lower body <NUM>. In more detail, the third space S3 may be opened to a lower side, and the second bag body <NUM> may cover the third space S2 from a lower side in a state of being inserted into the third space S3. In addition, in the second bag body <NUM>, a passage 64a through which the sub pressing part <NUM> and the inner space of the second flexible bag <NUM> communicate with each other may be provided.

The sub pressing part <NUM> may control an internal pressure of the second flexible bag <NUM> by introducing a fluid through the passage 64a. The term "fluid" encompasses a liquid and a gas. That is, the sub pressing part <NUM> may apply the pneumatic or hydraulic pressure to a target area <NUM>. For example, the sub pressing part <NUM> may include a pneumatic pump or a hydraulic pump.

A distance d1 between the pouch film F and the first bag body <NUM> may be less than a distance d2 between the pouch film F and the second bag body <NUM>. Thus, the first flexible bag <NUM> may uniformly press the target area <NUM> as a whole, while the second flexible bag <NUM> may press only a portion of the target area <NUM> according to a degree of expansion, or the target area <NUM> may be pressed as a whole. This will be described in detail later.

<FIG> is a flowchart illustrating a molding method performed using the molding apparatus according to further another embodiment of the present invention, and <FIG> are views for explaining an operation of the molding apparatus according to further another embodiment of the present invention.

A molding method according to this embodiment may include a preparation process (S10) in which a pouch film F is inserted between a die <NUM> and a stripper <NUM>, a fixing process (S20) in which the stripper <NUM> fixes the pouch film F, and a pressing process (S30') of applying a pneumatic or hydraulic pressure to the pouch film F.

The preparation process (S10) and the fixing process (S20) refer to the contents described above.

In the pressing process (S30'), a pressing part <NUM> may adjust an internal pressure of a first flexible bag <NUM>, and a sub pressing part <NUM> may adjust an internal pressure of a second flexible bag <NUM> to apply a pneumatic or hydraulic pressure to a pouch film F. Thus, an isotropic pressure may act on the pouch film F, more specifically, a target area <NUM>, and the target area <NUM> may be elongated into a first space S1 so as to be molded into a cup part <NUM>.

In more detail, the pressing process (S30') may include a preliminary molding process (S31'), a secondary molding process (S32'), and a secondary molding process (S33').

Referring to <FIG>, in the preliminary molding process (S31'), the first flexible bag <NUM> may press the pouch film F, more specifically, the target area <NUM>. Here, the pressure applied to the target area <NUM> may be appropriately adjusted so that a remaining thickness of the target area <NUM> is not excessively thin.

In more detail, the first flexible bag <NUM> may be expanded by the pressing part <NUM> to apply the isotropic pressure to the target area <NUM>. Thus, the target area <NUM> may be uniformly elongated into the first space S1 to form a predetermined curved surface. The curved surface of the target area <NUM> may be formed to have the lowest central portion and have a height that gradually increases toward the inner circumference of the first space S1.

Referring to <FIG>, in the primary molding process (S32'), the second flexible bag <NUM> may be expanded into the first space S1 to press the pouch film F, more specifically, the target area <NUM>. Here, the first flexible bag <NUM> may continuously maintain the pressure applied to the target area <NUM>.

Since the second bag body <NUM> is disposed farther than the first bag body <NUM> with respect to the pouch film F, the second flexible bag <NUM> may be in contact with a portion of a central portion of the target area <NUM> in the primary molding process S32'. Here, the internal pressure of the second flexible bag <NUM> may be higher than the internal pressure of the first flexible bag <NUM>.

Thus, a portion of the target area <NUM> may be formed convex upward while being pressed between the first flexible bag <NUM> and the second flexible bag <NUM>, and the other portion of the target area <NUM> may be spaced apart from the second flexible bag <NUM> and be in contact with or adjacent to an inner circumference of the first space S1. Hereinafter, the portion of the target area <NUM> will be referred to as a first area <NUM>, and the other portion of the target area <NUM> will be referred to as a second area <NUM>.

Since the first area and the second area <NUM> are formed to be previously divided into each other in the primary molding process (S32'), the second area <NUM> may be easily elongated in the subsequent secondary molding process (S33'). Thus, there is an advantage that the cup part <NUM> is deeply molded without wrinkles due to buckling on the circumferential surface <NUM> of the cup part <NUM>.

In addition, since a portion at which the first area <NUM> and the second area <NUM> meet each other forms an acute angle, in the subsequent secondary molding process (S33'), the second area <NUM> may be in easily close contact with the inner circumference of the first space S1. Thus, the circumferential surface <NUM> of the cup part <NUM> may be formed to be perpendicular to the bottom surface <NUM>, and a curvature radius of each of an edge and corner of the cup part <NUM> may be minimized to prevent stress from being concentrated to the corner of the cup part <NUM>.

Referring to <FIG>, in the secondary molding process (S33'), the internal pressures of the first flexible bag <NUM> and the second flexible bag <NUM> may be adjusted to be equal to each other. In addition, the inner pressure of each of the first flexible bag <NUM> and the second flexible bag <NUM> may be greater than the inner pressure of the second flexible bag <NUM> in the primary molding process (S32').

Thus, the first area <NUM> may be flatly pressed between the first flexible bag <NUM> and the second flexible bag <NUM>, and the second area <NUM> may be in close contact with the inner circumference of the first space S1. Thus, the molding of the cup part <NUM> may be completed.

Claim 1:
A molding apparatus for molding a cup part (<NUM>) in a pouch film (F), the molding apparatus comprising:
a die (<NUM>) on which the pouch film (F) is seated on a top surface thereof and in which a first space (S1) recessed from the top surface is defined;
a stripper (<NUM>) which is disposed above the die to fix the pouch film and in which a second space (S2) is defined at a position corresponding to the first space; and
a pressing part (<NUM>) configured to apply a pneumatic or hydraulic pressure to the pouch film through the second space so that a portion of the pouch film is elongated into the first space, the molding apparatus comprising:
a first punch (<NUM>) configured to be inserted into the first space (S1) and having a curved surface (<NUM>) that is convex toward the pouch film (F), the apparatus being characterized in having
a second punch (<NUM>) configured to be inserted into the first space (S1) and having a plane (<NUM>) facing the pouch film (F).