Patent Description:
Demand for a secondary battery as an energy source for mobile devices, electric vehicles, etc. has abruptly increased. In particular, demand for a lithium secondary battery, which has high energy density and high discharge voltage, is high.

Based on the shape and material thereof, the lithium secondary battery may be classified as a cylindrical secondary battery made of a metal material, a prismatic secondary battery made of a metal material, or a pouch-shaped secondary battery made of a laminate sheet. The pouch-shaped secondary battery has advantages in that the pouch-shaped secondary battery is stacked with high degree of integration, thereby having high energy density per unit weight, is manufactured at low cost, and is easily deformable. Consequently, the pouch-shaped secondary battery is used in various devices.

The pouch-shaped secondary battery uses a laminate sheet including an outer coating layer, a metal blocking layer, and an inner adhesive layer as a battery case, and is configured to have a structure in which an electrode assembly is received in a receiving portion formed in the laminate sheet together with an electrolytic solution.

In order to shape an electrode assembly receiving portion in the pouch-shaped secondary battery, a deep drawing method of disposing a laminate sheet on a die, fixing the laminated sheet using a gripper, and pressing the laminate sheet using a punch is used. During deep drawing, however, external defects, such as pin-holes or cracks, are formed on the outer surface of the laminate sheet due to limited softness of the laminate sheet and the force of friction between the punch and the laminate sheet.

Even though surface roughness of the punch that contacts the laminate sheet is extremely reduced in order to prevent formation of such external defects, it is difficult to prevent external defects from being formed on the laminate sheet due to friction caused by repeated punching. Particularly, in the case in which the thickness of the laminate sheet, specifically the metal blocking layer, is small, shapeability of the laminate sheet is reduced, whereby pin-holes or cracks may be more easily formed. For this reason, it is difficult to shape the electrode assembly receiving portion so as to have a large depth, whereby it is difficult to manufacture a high-capacity lithium secondary battery.

Patent Document <NUM> discloses a sheathing member for batteries, the sheathing member including an outer layer including a heat-resistant resin film, a metal foil layer, and an inner layer including a thermoplastic resin film having a lubricant added thereto, wherein the lubricant is attached between the outer layer and the inner layer.

In Patent Document <NUM>, the lubricant is attached between the outer layer and the inner layer, whereby sliding of the outer layer relative to a second die and sliding of the inner layer relative to a first die are improved, and therefore it is possible to inhibit bending of the outer circumferential portion of the sheathing member for batteries.

Patent Document <NUM> discloses a packaging material for shaping including a substrate layer, as an outer layer, a thermally fusible resin layer, as an inner layer, and a metal foil layer disposed between the two layers, wherein the thermally fusible resin layer is configured to have a single layer structure or a multilayer structure, and the innermost layer of the thermally fusible resin layer is made of a resin composition containing an anti-blocking agent, a slip agent, and a fluoropolymer-based lubricant.

In Patent Document <NUM>, slip between the surface of the innermost layer of the thermally fusible resin layer and the surface of a shaping die is improved when the packaging material is shaped, whereby shapeability may be improved.

Patent Document <NUM> and Patent Document <NUM> do not recognize a problem in that defects are generated as the result of the sheathing member for batteries being elongated during drawing, and do not suggest a method of solving the problem.

Patent document D3 discloses a battery case shaping apparatus comprising a punch (reference <NUM>)configured to press a laminate sheet (reference <NUM>) in order to shape a battery case; a die (reference <NUM>) in which an accommodation portion is formed, the accommodation portion having a size corresponding to an electrode assembly receiving portion that is shaped by the punch (paragraph [<NUM>]; a holder (reference <NUM>) configured to fix an outer periphery of the laminate sheet (paragraph [<NUM>] and <FIG>); and an elastic separator (reference <NUM>) located under the punch in order to prevent direct contact between the punch and the laminate sheet (paragraph [<NUM>]).

Therefore, there is a high necessity for technology capable of preventing damage to the external appearance of a laminate sheet and improving shapeability during shaping of the laminate sheet.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a battery case shaping apparatus capable of reducing the force of friction between a punch configured to press a laminate sheet in order to shape a battery case and the laminate sheet due to contact therebetween, thereby preventing damage to the laminate sheet, and a battery case shaping method using the same.

In order to accomplish the above object, a battery case shaping apparatus according to the present invention includes a punch configured to press a laminate sheet in order to shape a battery case, a die in which an accommodation portion is formed, the accommodation portion having a size corresponding to an electrode assembly receiving portion that is shaped by the punch, a holder configured to fix the outer periphery of the laminate sheet, and an elastic separator located under the punch in order to prevent direct contact between the punch and the laminate sheet.

In the battery case shaping apparatus according to the present invention, the elastic separator is fixed to the holder.

In the battery case shaping apparatus according to the present invention, the elastic separator may be fixed to a lower part of the side surface of the holder.

In the battery case shaping apparatus according to the present invention, the lower surface of the punch may be configured to be parallel to the upper surface of the elastic separator before the battery case is shaped by the punch.

In the battery case shaping apparatus according to the present invention, a liquid lubricant may be added into a space formed by the elastic separator and the holder.

In the battery case shaping apparatus according to the present invention, a recess may be formed in at least a portion of the lower surface of the punch.

In the battery case shaping apparatus according to the present invention, a pad may be disposed in and at a lower part of the accommodation portion of the die.

In the battery case shaping apparatus according to the present invention, the pad may be made of an elastic material and may include a central part that convexly protrudes.

In the battery case shaping apparatus according to the present invention, the protruding central part of the pad may be configured to contract as the result of pressing by the punch, whereby the overall thickness of the pad may become uniform.

In the battery case shaping apparatus according to the present invention, the elastic separator may be a watertight elastic separator.

The present invention provides a battery case shaping method using the battery case shaping apparatus.

Specifically, the battery case shaping method may include (a) disposing the laminate sheet on the die, (b) fixing the laminate sheet to the die using the holder having the elastic separator attached to the holder, and (c) pressing the elastic separator and the laminate sheet using the punch.

The battery case shaping method according to the present invention may further include adding a liquid lubricant into a space formed by the elastic separator and the holder between step (b) and step (c).

In the battery case shaping method according to the present invention, in step (c), the pressing may be performed until the pad disposed in the lower part of the accommodation portion of the die is compressed and flat.

In the battery case shaping method according to the present invention, when compression of the pad starts, liquid lubricant may move to the edge of the lower surface of the punch.

In the battery case shaping method according to the present invention, the region of the laminate sheet that is elongated by the pressing in step (c) may be a side surface of the electrode assembly receiving portion and an outer circumferential portion of the bottom of the electrode assembly receiving portion.

As is apparent from the above description, in the present invention, an electrode assembly receiving portion is shaped in the state in which an elastic separator is interposed between a laminate sheet and a punch, whereby it is possible to prevent direct contact between the punch and the laminate sheet, and therefore it is possible to minimize a stick-slip effect that occurs on the surface of the punch and the surface of the laminate sheet.

In addition, a liquid lubricant is added, whereby it is possible to reduce the force of friction between the punch and the laminate sheet.

In addition, it is possible to extend an elongation region of the laminate sheet as the result of addition of the liquid lubricant and the elastic separator, whereby it is possible to prevent the laminate sheet from being locally excessively elongated and thus thinned.

As described above, it is possible to reduce frictional force during a manufacturing process and to prevent the thickness of a side wall of the electrode assembly receiving portion of the battery case from being locally excessively reduced, whereby it is possible to prevent pin-holes or cracks from being formed on the battery case.

Also, in the case in which a battery case shaping apparatus and method according to the present invention are used even though laminate sheets having the same thickness are used, it is possible to more deeply form the electrode assembly receiving portion, and therefore it is possible to increase capacity of a battery cell and to improve energy density of the battery cell.

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

<FIG> is a front view of a battery case manufacturing apparatus according to a first embodiment of the present invention, and <FIG> is an exploded perspective view of the battery case manufacturing apparatus according to the first embodiment of the present invention.

Referring to <FIG> and <FIG>, the battery case manufacturing apparatus <NUM> includes a punch <NUM> configured to press a laminate sheet <NUM> in order to shape a battery case, a die <NUM> having formed therein an accommodation portion <NUM> having a size corresponding to an electrode assembly receiving portion that is shaped by the punch, a holder <NUM> configured to fix the outer periphery of the laminate sheet <NUM>, and an elastic separator <NUM> located under the punch <NUM> in order to prevent direct contact between the punch <NUM> and the laminate sheet <NUM>.

In order to manufacture a pouch-shaped battery case using the laminate sheet, the laminate sheet <NUM> is disposed on the die <NUM> having formed therein the accommodation portion <NUM> having the size corresponding to the electrode assembly receiving portion, the outer periphery of the laminate sheet <NUM> is fixed to the die using the holder <NUM>, and the laminate sheet <NUM> is pressed by the punch <NUM>, whereby the electrode assembly receiving portion may be shaped.

At this time, in order to prevent direct contact between the laminate sheet and the punch, the elastic separator <NUM> is disposed between the laminate sheet and the punch.

If the laminate sheet and the punch directly contact each other, slip does not easily occur due to friction between the surfaces of the laminate sheet and the punch. As a result, the region of the laminate sheet that is elongated is narrowed, and therefore only a local region of the laminate sheet is elongated. Specifically, since the portion of the laminate sheet that becomes a side wall of the electrode assembly receiving portion when the laminate sheet is shaped into a battery case is mainly elongated, the thickness of the portion is excessively reduced, and therefore the battery case is easily damaged.

Since a stick-slip phenomenon easily occurs on the surface of the laminate sheet and the surface of the punch, as described above, the laminate sheet may be locally excessively elongated, and therefore a battery case shaping defect rate may be increased.

In the present invention, the laminate sheet <NUM> is pressed by the punch <NUM> in the state in which the elastic separator <NUM> is disposed between the laminate sheet <NUM> and the punch <NUM>, and therefore the surface of the laminate sheet and the surface of the punch do not directly contact each other. Consequently, it is possible to solve a conventional problem in that the laminate sheet is scratched due to a non-smooth surface of the punch or introduction of foreign matter between the punch and the laminate sheet.

The x-axis width w1 of the punch <NUM> may be less than the x-axis distance w2 between opposite sides of the die, and the x-axis distance w2 between opposite sides of the die may be less than the x-axis distance w3 between opposite sides of the holder.

Consequently, the punch may easily enter the die through the holder.

<FIG> is a sectional view of a battery case manufacturing apparatus according to a second embodiment of the present invention.

Referring to <FIG>, the battery case shaping apparatus <NUM> includes a punch <NUM> configured to press a laminate sheet <NUM> in order to shape a battery case, a die <NUM> having formed therein an accommodation portion <NUM> having a size corresponding to an electrode assembly receiving portion that is shaped by the punch, a holder <NUM> configured to fix the outer periphery of the laminate sheet <NUM>, and an elastic separator <NUM> located under the punch <NUM> in order to prevent direct contact between the punch <NUM> and the laminate sheet <NUM>. The elastic separator <NUM> is fixed to the holder <NUM>. The holder <NUM>, to which the elastic separator <NUM> is fixed, is disposed on the laminate sheet <NUM>, whereby the laminate sheet is fixed.

Since the elastic separator <NUM> is fixed to the holder <NUM>, as described above, the state in which the elastic separator <NUM> is fixed to the holder may be stably maintained when the laminate sheet <NUM> is pressed by the punch <NUM>.

For example, the elastic separator <NUM> may be attached to the lower surface of the holder <NUM>, or may be fixed to the lower part of the side surface of the holder <NUM>. When the elastic separator <NUM> is attached to the lower surface of the holder <NUM>, the force of fixing the laminate sheet <NUM> may be further increased by a microscopically protruding portion formed as the result of coupling between the elastic separator <NUM> and the holder <NUM>. When the elastic separator <NUM> is fixed to the lower part of the side surface of the holder <NUM>, particularly when the elastic separator <NUM> is inserted into and fixed to a recess formed in the lower part of the side surface of the holder <NUM>, the force of coupling between the elastic separator <NUM> and the holder <NUM> is further increased. As a result, coupling between the elastic separator and the holder is maintained even when the elastic separator <NUM> is excessively elongated. When the depth of the receiving portion is large, a more advantageous effect may be achieved.

Before the battery case is shaped by the punch, the lower surface of the punch is located parallel to the upper surface of the elastic separator <NUM>. In addition, the elastic separator and the laminate sheet are located parallel to each other. When the elastic separator is pressed by the punch, therefore, the entire area of the punch may apply uniform pressure to the entire area of the elastic separator and the laminate sheet.

In this specification, force generated by the punch is applied to the elastic separator and the laminate sheet with the same magnitude and in the same direction, and deformation of the laminate sheet is identical to deformation of the elastic separator.

<FIG> is a sectional view of a battery case manufacturing apparatus according to a third embodiment of the present invention, and <FIG> is an exploded perspective view of the battery case manufacturing apparatus according to the third embodiment of the present invention.

Referring to <FIG> and <FIG>, the battery case shaping apparatus <NUM> includes a punch <NUM> configured to press a laminate sheet <NUM> in order to shape a battery case, a die <NUM> having formed therein an accommodation portion <NUM> having a size corresponding to an electrode assembly receiving portion that is shaped by the punch, a holder <NUM> configured to fix the outer periphery of the laminate sheet <NUM>, and an elastic separator <NUM> located under the punch <NUM> in order to prevent direct contact between the punch <NUM> and the laminate sheet <NUM>.

The elastic separator <NUM> is fixed to the holder <NUM>. As a result, a space having the elastic separator as a lower surface thereof and the inner surface of the holder <NUM> as a side wall thereof is formed, and a liquid lubricant <NUM> is added into the space. Since the elastic separator is a watertight elastic separator, the liquid lubricant is not discharged through the elastic separator, and is movable only in the space.

The liquid lubricant remarkably reduces the force of friction between the punch and the elastic separator, whereby the surface of the elastic separator and the surface of the punch may very smoothly slip relative to each other.

As a result, the region of the laminate sheet that is elongated by the punch is increased, and therefore the average elongation of the elongated region may be reduced. For example, the thickness of the laminate sheet in an elongated state may be about <NUM>% or more the thickness of the laminate sheet before elongation.

For example, at least one selected from the group consisting of hydrocarbon-based oil, such as liquid paraffin, grease, mineral vegetable oil, an emulsified oil, an anti-emulsifier, a pour point depressant, a viscosity modifier, an antifoaming agent, mineral oil including pure mineral oil or pure mineral oil including an additive, a fatty oil including animal oil and vegetable oil, a blended oil of mineral oil and a fatty oil, and a synthetic oil may be used as the liquid lubricant.

In the case in which the liquid lubricant is used, as described above, it is possible to prevent a local region of the laminate sheet from being excessively elongated.

<FIG> is a vertical sectional view of a battery case manufactured using the battery case manufacturing apparatus according to the present invention. Referring to <FIG>, an electrode assembly receiving portion <NUM> is concavely formed in the battery case <NUM>. The electrode assembly receiving portion <NUM> may be constituted by a bottom <NUM> of the electrode assembly receiving portion and a side surface <NUM> of the electrode assembly receiving portion.

If no liquid lubricant is used, unlike the present invention, the laminate sheet is elongated only at a main elongation region E1. As a result, the average elongation of the main elongation region is high, whereby this region is weakened, and therefore the battery case may be easily damaged.

Since the liquid lubricant is used in the present invention, however, slip occurs well between the surface of the punch and the surface of the elastic separator. Consequently, the elongation region is extended to an additional elongation region E2 in addition to the main elongation region E1. That is, the region of the laminate sheet that is elongated may be the side surface <NUM> of the electrode assembly receiving portion and the outer circumferential portion of the bottom <NUM> of the electrode assembly receiving portion.

As the elongation region is extended, as described above, the average elongation is reduced, whereby it is possible to reduce a thickness reduction rate of the battery case even after the battery case is shaped, and it is possible to prevent the battery case from being locally weakened.

In the battery case manufactured using the battery case shaping apparatus according to the present invention, the thickness of the smallest thickness portion of the battery case may be <NUM>% or more the thickness of the largest thickness portion of the battery case.

Referring back to <FIG> and <FIG>, a pad <NUM> is disposed in the accommodation portion <NUM> of the die <NUM> at the lower part thereof.

The pad <NUM> may be made of an elastic material so as to be contracted by the punch <NUM>. The pad <NUM> may be formed in a quadrangular shape when viewed in plan, and may be configured to have a structure in which a central part of the pad convexly protrudes and the thickness of the pad is gradually decreased toward the outer circumferential portion thereof. When the laminate sheet is pressed by the punch <NUM> so as to be shaped, first, the protruding central part of the pad comes into contact with the laminate sheet moved downwards by the punch. Subsequently, when the laminate sheet is continuously pressed downwards by the punch, the protruding central part of the pad is contracted, whereby the overall thickness of the pad becomes uniform. As a result, the bottom of the electrode assembly receiving portion may become flat.

In addition, since the elastic pad <NUM> is disposed, it is possible to prevent the outside of the lower surface of the laminate sheet from being scratched.

<FIG> is a vertical sectional view of a central part of a punch according to the present invention.

Referring to <FIG>, a recess <NUM> or <NUM> is formed in the lower surface of the punch <NUM> or <NUM>.

The recess <NUM> formed in the punch <NUM> is configured such that the central part of the lower surface of the punch becomes concave, and the recess <NUM> formed in the punch <NUM> is configured such that the entirety of the lower surface of the punch becomes concave.

A space is formed in the lower surface of the punch by the recess formed as described above. When the elastic separator and the laminate sheet are pressed by the punch, a portion of the liquid lubricant is gathered, and the remainder of the liquid lubricant moves to the edge of the lower surface of the punch.

The force of friction between the central part of the punch and the elastic separator is reduced by the liquid lubricant gathered in the recess.

<FIG> shows a battery case shaping method according to the present invention from left to right and from top to bottom.

The battery case shaping method according to the present invention includes a step of disposing a laminate sheet <NUM> on the die <NUM>, a step of fixing the laminate sheet <NUM> to the die <NUM> using the holder <NUM>, to which the elastic separator <NUM> is attached, and a step of pressing the elastic separator <NUM> and the laminate sheet <NUM> using the punch <NUM>.

Before the laminate sheet <NUM> is pressed by the punch <NUM> after the laminate sheet <NUM> is fixed to the die <NUM>, the liquid lubricant <NUM> is added to the space formed by the elastic separator <NUM> and the holder <NUM>. Since the elastic separator according to the present invention is a watertight elastic separator, the liquid lubricant is not discharged to the outside of the elastic separator.

In the step of pressing the laminate sheet <NUM> using the punch <NUM>, pressing is performed until the pad <NUM> disposed in the lower part of the accommodation portion of the die <NUM> is compressed and flat. Since the pad <NUM> is configured to have a structure in which the central part of the pad protrudes and the thickness of the pad is gradually decreased toward the outer circumferential portion thereof, first, the laminate sheet <NUM> comes into contact with the protrude central part of the pad <NUM>.

When compression of the pad <NUM> starts, the central part of the pad <NUM> is in contact with the laminate sheet <NUM>, but a space is formed between the outer circumferential portion of the pad <NUM> and the laminate sheet <NUM>. As the result of pressing, the liquid lubricant <NUM> on the elastic separator <NUM> moves to the space formed between the laminate sheet <NUM> and the outer circumferential portion of the pad <NUM>, i.e., the edge of the lower surface of the punch <NUM>.

In the case in which a recess is formed in the lower surface of the punch <NUM>, a portion of the liquid lubricant may be gathered in the recess, and therefore it is possible to reduce the force of friction between the punch and the elastic separator at the lower surface of the punch.

As the punch <NUM> is inserted into the accommodation portion of the die <NUM>, the liquid lubricant <NUM> moves to the edge of the lower surface of the punch <NUM>, and eventually moves along the side surface of the punch <NUM>. As a result, the liquid lubricant <NUM> may be present not only between the lower surface of the punch <NUM> and the surface of the elastic separator <NUM> but also between the side surface of the punch <NUM> and the surface of the elastic separator <NUM>, whereby it is possible to reduce the force of friction between the punch and the elastic separator. With progress of pressing, the liquid lubricant <NUM> more widely spreads due to a capillary phenomenon.

In the present invention, as described above, the pad, the central part of which is convex, is disposed at the lower part of the accommodation portion of the die, whereby the liquid lubricant may easily move to the main elongation region and the additional elongation region of the laminate sheet. Consequently, the force of friction between the surface of the elastic separator and the surface of the punch is minimized, whereby it is possible to widely secure the additional elongation region of the laminate sheet, and therefore it is possible to manufacture a battery case having a small local reduction in thickness.

Those skilled in the art to which the present invention pertains will appreciate that various applications and modifications are possible within the category of the present invention based on the above description.

Claim 1:
A battery case shaping apparatus (<NUM>, <NUM>, <NUM>) comprising:
a punch (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured to press a laminate sheet (<NUM>, <NUM>, <NUM>) in order to shape a battery case (<NUM>);
a die (<NUM>, <NUM>, <NUM>) in which an accommodation portion (<NUM>, <NUM>, <NUM>) is formed, the accommodation portion (<NUM>, <NUM>, <NUM>) having a size corresponding to an electrode assembly receiving portion (<NUM>) that is shaped by the punch (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
a holder (<NUM>, <NUM>, <NUM>) configured to fix an outer periphery of the laminate sheet; and
an elastic separator (<NUM>, <NUM>, <NUM>) located under the punch in order to prevent direct contact between the punch (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and the laminate sheet (<NUM>, <NUM>, <NUM>), characterized in that the elastic separator (<NUM>, <NUM>, <NUM>) is fixed to the holder (<NUM>, <NUM>, <NUM>).