Patent Description:
Recently, with rapid progress in miniaturization and weight reductions of mobile electronic devices, demand for a secondary battery as an energy source thereof is rapidly increasing.

A secondary battery is a battery capable of repeated charging and discharging because mutual conversion between chemical energy and electrical energy is reversible.

A manufacturing process of the secondary battery is largely divided into an electrode process for manufacturing an electrode, an assembly process for manufacturing a battery, and a chemical conversion process for imparting electrical characteristics to the battery.

Thereamong, the electrode process is the most important process among secondary battery manufacturing processes, and is divided into a mixing process, a coating process, a rolling process, a cutting process, a drying process, and the like.

According to the electrode process, an active material (hereinafter, a mixture layer) prepared in the mixing process is applied to both surfaces of a current collector in the coating process, and is then compressed on both surfaces of the current collector through the rolling process.

That is, a current collector (hereinafter referred to as an electrode sheet) coated with a mixture layer on both surfaces thereof is compressed while passing through a pair of rolling rolls in the rolling process, so that adhesion between the current collector and a slurry is improved, and as a thickness of the electrode sheet is reduced, energy density is improved.

Meanwhile, since the electrode sheet undergoing the rolling process becomes reduced only in thickness without changing a length thereof, mixture density (g/cc) of the electrode is determined through the rolling process.

In particular, since an anode electrode cannot excessively increase a degree of pressure applied to the electrode sheet due to a crystal structure of a carbon-based (e.g., graphite) active material, there is a limit to increasing the mixture density thereof through the rolling process, but since a cathode electrode does not have such limitations, the rolling process of the cathode electrode is directly related to the energy density of the secondary battery.

Meanwhile, in the conventional rolling process, a rolling roll having a large diameter was used to improve rolling performance. However, when force applied to the electrode sheet is the same, as a diameter of the rolling roll increases, a contact area thereof with the electrode sheet increases and the pressure applied to the electrode sheet decreases, so there is a limit to rolling the electrode sheet at high density. Prior art document <CIT> discloses a rolling apparatus comprising a pair of rolling rolls provided to pass an electrode, in which each rolling roll has a crown curved portion consisting of a flat part and a crown curved surface. Therein, the crown surface reveals a smaller diameter toward the edge, and the size of the crown surface may be determined as a quadratic function of linear pressure. During rolling and passing between the pair of rolling rolls, the thickness of the electrode decreases until target thickness and density values are reached. Furthermore, document <CIT> is known, which discloses a lithium secondary battery comprising a cathode including a cathode current collector and a cathode active material layer positioned on the cathode current collector, a non-aqueous electrolyte, and an anode. In said lithium secondary battery, the cathode density may be in a range from <NUM>/cc to <NUM>/cc. Furthermore, document <CIT> is known, which discloses a hot-press machine for pressing a material between a pair of first and second rollers that are opposed to each other. Additionally, a plurality of bearings is disclosed, which rotatably support a roller spindle. The pressing apparatus rolls an electrode material by sandwiching and transporting the electrode material, that is conveyed through a rolling pressure space, using first and second pressure rollers. A predetermined thickness dimension of the electrode material may be obtained. A correction mechanism that corrects the axial deflection of the first and second rollers is further disclosed. Furthermore, document <CIT> is known, which discloses a rolling press machine for a secondary battery electrode material. The rolling press machine performs continuous compressing work on the electrode material with high working accuracy while preventing thermal deformation of rolls due to the mechanical friction heat of a bearing part during long-time operation.

An aspect of the present disclosure is to provide a rolling apparatus for a secondary battery electrode sheet, as recited in claim <NUM>, capable of manufacturing a secondary battery having improved energy density.

In addition, an aspect of the present disclosure, not covered by the appended claims, is to provide a cathode electrode having improved energy density and a secondary battery including the same.

As recited in claim <NUM>, a rolling apparatus for a secondary battery electrode sheet includes:
a transfer unit transferring an electrode sheet having an electrode mixture layer applied to at least one surface thereof in a first direction; a rolling roll pressing the electrode sheet in a second direction, intersecting the first direction; and a support portion coupled to a rotational axis of the rolling roll to support rotation of the rolling roll, wherein the rolling roll may have a shape in which a central portion thereof in an axial direction protrudes further toward the electrode sheet than both end portions of thereof in an axial direction.

According to one embodiment of the present invention, the rolling roll may have a height difference of <NUM> or less between the most protruding portion and the most recessed portion thereof in the axial direction.

According to one embodiment of the present invention, both end portions of the rolling roll in the axial direction may have a shape of being recessed more deeply in a direction away from the central portion thereof in the axial direction.

According to one embodiment of the present invention, the rolling roll may comprise: a first rolling roll pressing one surface of an electrode sheet; and a second rolling roll pressing the other surface of the electrode sheet, wherein a distance between the first rolling roll and the second rolling roll may increase from the central portion thereof in the axial direction toward both end portions thereof in the axial direction.

According to one embodiment of the present invention, when the first rolling roll and the second rolling roll press the electrode sheet, both end portions of the first rolling roll and the second rolling roll may not be in contact with each other.

Accoring to the present invention and as recited in claim <NUM>, the rolling roll is formed to have a diameter in a range of <NUM> to <NUM>.

According to the present invention and as recited in claim <NUM>, the support portion comprises: a first support portion disposed outside the rolling roll in a longitudinal direction of the rotational axis, the first support portion including a first bearing that is pressed in a direction in which the rolling roll presses the electrode sheet, and a first housing in which the first bearing is accommodated; and a second support portion disposed outside the first support portion in a longitudinal direction of the rotational axis, the second support portion including a second bearing that is pressed in a direction, opposite to the direction in which the first bearing is pressed, and a second housing in which the second bearing is accommodated.

According to the present invention and as recited in claim <NUM>, the first bearing comprises a four-row roller bearing.

According to one embodiment of the present invention, the first housing may comprise a refrigerant passage through which a refrigerant is supplied.

According to one embodiment of the present invention, the refrigerant passage may be provided to surround an external surface of the first bearing.

According to an aspect of the present disclosure not covered by the appended claims, a cathode electrode manufactured by the rolling apparatus may have a mixture density of <NUM>(g/cc) or more and <NUM>(g/cc) or less.

According to an aspect of the present disclosure not covered by the appended claims, a secondary battery may comprise: the cathode electrode manufactured by the roling apparatus; and an anode electrode.

<FIG> is a schematic side view of a rolling apparatus according to an embodiment of the present disclosure, and <FIG> is a schematic front view of region I in <FIG>.

A rolling apparatus for a secondary battery electrode sheet (hereinafter, referred to as a rolling apparatus) <NUM> according to an embodiment of the present disclosure may be an apparatus for rolling an electrode sheet to a predetermined thickness in a rolling process during a process for manufacturing a secondary battery. Preferably, the rolling apparatus <NUM> according to an embodiment of the present disclosure may be used to manufacture a cathode electrode.

Referring to <FIG>, the rolling apparatus <NUM> may include an unwinder <NUM> and a rewinder <NUM>. The unwinder <NUM> and the rewinder <NUM> may be sequentially disposed in a transfer direction (hereinafter, referred to as a first direction) (A) of the electrode sheet <NUM>.

Meanwhile, although not illustrated in the drawing, one or more auxiliary rolls may be provided between the unwinder <NUM> and the rewinder <NUM> to assist in the transfer of the electrode sheet <NUM>.

The unwinder <NUM> and the rewinder <NUM> may rotate in the same direction in synchronization with each other. For example, the unwinder <NUM> and the rewinder <NUM> may rotate in the first direction (A) in synchronization with each other. The unwinder <NUM> and the rewinder <NUM> may also be referred to as a transfer unit.

The electrode sheet <NUM> may be wound around the unwinder <NUM>, and the unwinder <NUM> may supply the electrode sheet <NUM> in the first direction (A) while rotating. The rewinder <NUM> may wind the electrode sheet <NUM>. In detail, the rewinder <NUM> may wind the electrode sheet <NUM> rolled by a rolling roll <NUM> to be described later.

Referring to <FIG>, a rolling roll <NUM> rolling the electrode sheet <NUM> may be disposed between the unwinder <NUM> and the rewinder <NUM> based on a first direction (A).

The rolling roll <NUM> may be provided as a pair thereof. The rolling roll <NUM> may include a first rolling roll <NUM> disposed on one side of the electrode sheet <NUM> to press one surface of the electrode sheet <NUM> and a second rolling roll <NUM> disposed on the other side of the electrode sheet <NUM> to press the other surface of the electrode sheet <NUM>.

Based on the drawings, the first rolling roll <NUM> is disposed on an upper side of the electrode sheet <NUM> to press an upper surface of the electrode sheet <NUM>, and the second rolling roll <NUM> is disposed on a lower side of the electrode sheet <NUM> to press a lower surface of the electrode sheet <NUM>.

The electrode sheet <NUM> is supplied between the first rolling roll <NUM> and the second rolling roll <NUM>, and may be rolled while passing through a pair of rolling rolls <NUM>. The rolling roll <NUM> may press the electrode sheet <NUM> in a second direction (B), intersecting the first direction (A) in which the electrode sheet <NUM> is transferred. The second direction (B) in which the rolling roll <NUM> presses the electrode sheet <NUM> may be a direction, perpendicular to the first direction (A).

Referring to <FIG>, the electrode sheet <NUM> supplied between a pair of rolling rolls <NUM> may have a form in which an electrode mixture layer <NUM> is applied to a current collector <NUM>. The electrode mixture layer <NUM> may be a layer including an electrode active material, a conductive agent, and a binder. The electrode mixture layer <NUM> may be compressed to the current collector <NUM> while passing through the pair of rolling rolls <NUM>.

Meanwhile, although the drawing illustrates that the electrode mixture layer <NUM> is applied to both surfaces of the current collector <NUM>, the electrode mixture layer <NUM> may be applied to at least one surface of the current collector <NUM>. For example, an electrode sheet <NUM>, disposed on the outermost side of an electrode assembly, may have an electrode mixture layer <NUM> applied to one surface thereof.

The electrode sheet <NUM> before passing through the rolling roll <NUM> and the electrode sheet <NUM> passing through the rolling roll <NUM> may have different thicknesses. In detail, the thickness of the electrode sheet <NUM> passing through the rolling roll <NUM> may be thinner than the thickness of the electrode sheet <NUM> before passing through the rolling roll <NUM>. In this case, since the length of the electrode sheet <NUM> is maintained, the mixture density and energy density of the electrode sheet <NUM> may be improved while passing through the rolling roll <NUM>.

The rolling roll <NUM> may be formed of a <NUM>% Cr Steel material having high surface strength. The <NUM>% Cr Steel material has deep heat treatment depth, so that local deformation of the rolling roll <NUM> may be prevented.

The rolling roll <NUM> may rotate while being coupled to a rotational axis <NUM>, having a length thereof in a width direction of the electrode sheet <NUM>. For example, the first rolling roll <NUM> may be coupled to a first rotational axis <NUM> to rotate, and the second rolling roll <NUM> may be coupled to the second rotational axis <NUM> to rotate.

Meanwhile, for convenience of description, the rolling roll <NUM> and the rotational axis <NUM> have been described as being separate components, but the rolling roll <NUM> and the rotational axis <NUM> may be integrally formed. That is, the rotational axis <NUM> may be a part of the rolling roll <NUM>.

Support portions <NUM> and <NUM> supporting the rotation of the rolling roll <NUM> may be coupled to the rotational axis <NUM>. The support portions <NUM> and <NUM> may be coupled to the rotational axis <NUM> to support a load of the rolling roll <NUM> while helping the rolling roll <NUM> smoothly rotate.

Referring to <FIG>, a rolling roll <NUM> is coupled to a central portion of the rotational axis <NUM> in a longitudinal direction, and a first support portion <NUM> is coupled to an external surface of the rolling roll <NUM>, and a second support portion <NUM> may be coupled to an external surface of the first support portion <NUM>. In addition, the first support portion <NUM> and the second support portion <NUM> may be provided on both sides of the rolling roll <NUM>.

The first support portion <NUM> may include a first housing <NUM> and a first bearing <NUM>.

The first housing <NUM> may include a hollow formed in a longitudinal direction of a rotational axis <NUM>, and the rotational axis <NUM> may be disposed in the hollow.

In addition, the first bearing <NUM> may be accommodated in the first housing <NUM>. In detail, the first bearing <NUM> may be disposed along a circumferential surface of the hollow. Accordingly, the rotational axis <NUM> may contact the first bearing <NUM> while being coupled to the first housing <NUM>.

According to the present disclosure, the first bearing <NUM> may be pressed in the direction in which the rolling roll <NUM> presses the electrode sheet <NUM>. For example, although not specifically illustrated in the drawings, the first bearing <NUM> may be connected to a static pressure cylinder through a rod, and the rolling roll <NUM> may be pressed in a direction in which the rolling roll <NUM> presses the electrode sheet <NUM> by extension of the rod.

Similarly, the second support portion <NUM> may also include a second housing <NUM> and a second bearing <NUM>. The second housing <NUM> may include a hollow formed in a longitudinal direction of a rotational axis <NUM>, and the rotational axis <NUM> may be disposed in the hollow.

In addition, the second bearing <NUM> may be accommodated in the second housing <NUM>. In detail, the second bearing <NUM> may be disposed along a circumferential surface of the hollow. Accordingly, the rotational axis <NUM> may contact the second bearing <NUM> while being coupled to the second housing <NUM>.

According to the present disclosure, the second bearing <NUM> may be pressed in a direction, opposite to the direction in which the rolling roll <NUM> presses the electrode sheet <NUM>. For example, although not specifically illustrated in the drawing, the second bearing <NUM> may be connected to a counter pressure cylinder through a rod, and may be pressed in a direction, opposite to the direction in which the rolling roll <NUM> presses the electrode sheet <NUM> by extension of the rod.

Specifically, the first bearing <NUM> is pressed in a central direction in a form of pushing the electrode sheet <NUM> to secure process performance by applying compressive force for rolling to the electrode sheet <NUM>, and the second bearing <NUM> relieves bending of the rolling roll <NUM> occurring when the electrode sheet <NUM> is rolled, and at the same time, when the electrode sheet <NUM> is not rolled, the second bearing <NUM> may be pressed in an opposite direction thereto to separate the first rolling roll <NUM> and the second rolling roll <NUM> disposed vertically, from each other.

Meanwhile, the rolling apparatus <NUM> according to an embodiment of the present disclosure proposes a rolling roll <NUM> having a new structure for rolling the electrode sheet <NUM> at high density.

Hereinafter, with reference to <FIG>, the rolling roll <NUM> according to an embodiment of the present disclosure will be described in detail.

<FIG> are conceptual diagrams of a shape of a rolling roll according to the prior art and an embodiment of the present disclosure, and <FIG> is a view illustrating a processed portion of a rolling roll according to an embodiment of the present disclosure.

Referring to <FIG>, in a conventional rolling roll <NUM>, a portion (a central portion of the rolling roll) for pressing the electrode sheet <NUM> is formed in a flat shape (a flat roll). On the other hand, referring to <FIG>, in a rolling roll <NUM> according to an embodiment of the present disclosure, the portion for pressing the electrode sheet <NUM> (hereinafter, referred to as the central portion of the rolling roll) is formed to protrude toward the electrode sheet <NUM> (a crown roll).

The rolling roll <NUM> has a shape in which a central portion 130a thereof in a direction of the rotational axis <NUM> (hereinafter, referred to as an axial direction) protrudes toward the electrode sheet <NUM> further than both end portions 130b thereof in the axial direction. Furthermore, the rolling roll <NUM> may be formed in a curved shape in which the central portion 130a thereof in the axial direction protrudes toward the electrode sheet <NUM>.

The rolling roll <NUM> may be formed to be longer than the electrode sheet <NUM> in the axial direction, and accordingly, a portion of the rolling roll <NUM> in the axial direction may not contact the electrode sheet <NUM> passing through the rolling roll <NUM>. In detail, when it is assumed that centers of the rolling roll <NUM> and the electrode sheet <NUM> in the axis direction coincide, both end portions 130b of the rolling roll <NUM> may not contact the electrode sheet <NUM>.

That is, both end portions 130b of the rolling roll <NUM> mentioned above may refer to a portion that does not contact the electrode sheet <NUM> passing through the rolling roll <NUM>. In addition, the central portion 130a of the rolling roll <NUM> may refer to a portion in contact with the electrode sheet <NUM> passing through the rolling roll <NUM>, and may partially include a portion, not in contact with the electrode sheet <NUM>. The central portion 130a may be a portion excluding both end portions 130b of the rolling roll <NUM>.

The rolling roll <NUM> according to an embodiment of the present disclosure may be manufactured by chamfering both end portions 130b. As illustrated in <FIG>, both end portions 130b of the rolling roll may be processed to a predetermined width (length in the axial direction) and depth. For example, both end portions 130b of the rolling roll may be processed such that a maximum processing depth d is within <NUM> in a width range of <NUM> to <NUM>.

Furthermore, when the electrode sheet <NUM> according to an embodiment of the present disclosure presses the electrode sheet <NUM>, it may include a curved surface in a form of a multi-order (quadratic, cubic, or quaternary) function so that the rolling roll <NUM> is bent to uniformly roll the electrode sheet <NUM> in a flat shape.

Meanwhile, with the above-described chamfering, both end portions 130b of the rolling roll <NUM> may have a more deeply recessed shape in a direction away from the central portion 130a in the axial direction. Therefore, a distance between the first rolling roll <NUM> and the second rolling roll <NUM> may increase from the central portion 130a to both end portions 130b in the axial direction, and through this structure, the side kiss phenomenon during conventional rolling illustrated in <FIG> may be solved.

<FIG> are conceptual views illustrating a cross- section of the rolling roll of <FIG> during rolling of an electrode sheet.

Referring to <FIG> , in a rolling roll <NUM>, which is flat in an axial direction, as in the prior art, a central portion of the rolling roll <NUM> moves up and down as an electrode sheet <NUM> is supplied between a first rolling roll <NUM> and a second rolling <NUM>, so that different degrees of pressures may be applied to the central portion of the electrode sheet <NUM> and a peripheral portion thereof (hereinafter referred to as an edge of the electrode sheet <NUM>) in the axial direction. That is, a relatively low degree of pressure was applied to the central portion of the electrode sheet <NUM>, and a relatively high degree of pressure was applied to the edge of the electrode sheet <NUM>. Accordingly, a tensile value acting on the edge of the electrode sheet <NUM> exceeds an allowable value, so that there may be a problem in which the electrode sheet <NUM> is broken.

In particular, when the electrode sheet <NUM> is rolled at high density, this phenomenon is intensified and a side kiss phenomenon in which both end portions of the first rolling roll <NUM> and the second rolling roll <NUM> come into contact with each other occurred. When the side kiss phenomenon occurs, since a load is applied between the rolling rolls <NUM> and <NUM> and the pressure applied to the electrode sheet <NUM> is relatively reduced, high-density rolling of the electrode sheet <NUM> is inhibited. In addition, since a difference in thickness due to a difference in pressure applied between the central portion and the edge of the electrode sheet <NUM> causes cell assembly failure, there is a limit to setting target rolling density to be high.

Referring to <FIG>, since the rolling roll <NUM> according to an embodiment of the present disclosure has a shape in which the central portion 130a in an axial direction protrudes toward the electrode sheet <NUM> more than both end portions 130b in the axial direction, the first rolling roll <NUM> and the second rolling roll <NUM>, even if the electrode sheet <NUM> is supplied between the first rolling roll <NUM> and the second rolling roll <NUM> so that the central portion 130a of the rolling roll <NUM> moves up and down, both end portions 130b of the rolling roll <NUM> may not come into contact with each other.

According to an embodiment of the present disclosure, when the electrode sheet <NUM> is supplied between the rolling rolls <NUM>, the protruding central portion 130a of the rolling roll <NUM> moves up and down, so that it has a height similar to that of both end portions 130b of the rolling roll <NUM>, so that one surface of the first both end portions <NUM> and one surface of the second both end portions <NUM> may be substantially parallel to each other, pressing the electrode sheet <NUM> in the axial direction.

Therefore, the rolling roll <NUM> according to an embodiment of the present disclosure may press the electrode sheet <NUM> with a constant pressure regardless of a position of the electrode sheet <NUM> in the axial direction, and may roll the electrode sheet <NUM> to a certain thickness. In addition, since a load of the rolling roll <NUM> is applied only to the electrode sheet <NUM>, the electrode sheet <NUM> may be manufactured to have higher density.

In addition, according to the invention, the rolling roll <NUM> is formed to have a diameter in a range of <NUM> to <NUM>. Preferably, the rolling roll <NUM> may be formed to have a diameter of <NUM>.

<FIG> are conceptual diagrams illustrating a comparison of a rolling length according to a diameter of a rolling roll.

Conventionally, as illustrated in <FIG>, the electrode sheet <NUM> was rolled using a rolling roll <NUM> having a diameter of about <NUM>, but in the present disclosure, as illustrated in <FIG>, the electrode sheet <NUM> is rolled using a rolling roll <NUM> having a diameter of about <NUM>. In the case of using the rolling roll <NUM> having a reduced diameter as described above, pressure applied to the electrode sheet <NUM> is increased, so that mixture density thereof may be improved.

In detail, when a distance between a first rolling roll <NUM> disposed on an upper side of the electrode sheet <NUM> and a second rolling roll <NUM> disposed on a lower side of the electrode sheet <NUM> are the same, assuming that the same degree of force is applied to the electrode sheet <NUM>, a contact area between the rolling roll <NUM> and the electrode sheet <NUM> decreases as the diameter of the rolling roll <NUM> decreases, so that the pressure applied to the electrode sheet <NUM> may be increased. Therefore, it is possible to roll the electrode sheet <NUM> at higher density.

In this regard, referring to <FIG>, a rolling length L2 during rolling using the rolling roll <NUM> having a diameter of <NUM> is shorter than a rolling length L1 during rolling using the rolling roll <NUM> having a diameter of <NUM>, which means that the contact area therebetween is reduced.

Meanwhile, as the diameter of the rolling roll <NUM> is reduced, the electrode sheet <NUM> can be rolled at high density, but the diameter of the rotational axis <NUM> is also reduced, so when the same load is applied thereto, there is a problem in that structural rigidity is weak, as compared to the conventional rolling roll <NUM>.

Accordingly, according to an embodiment of the present disclosure, the structure of the first bearing <NUM> for supplementing the structural rigidity of the rolling roll <NUM> may be applied.

<FIG> is a cross-sectional view of a first support portion according to an embodiment of the present disclosure.

Referring to <FIG>, a first bearing <NUM> is provided as a four-row roller bearing. According to an embodiment of the present disclosure, since the first bearing <NUM> is provided as four rows instead of being provided as two rows in the prior art, a contact area thereof with a rotating axis <NUM> may increase, thereby stably supporting rotation of a rotating axis <NUM> and a rolling roll <NUM>.

In addition, in a process in which the rolling roll <NUM> presses the electrode sheet <NUM>, heat may be generated by friction, or the like, between the rotating axis <NUM> and the first support portion <NUM> or the second support portion <NUM>, rotating together with the rolling roll <NUM>, and the generated heat may be conducted to the rolling roll <NUM>.

Accordingly, according to an embodiment of the present disclosure, the first housing <NUM> may include a refrigerant passage <NUM> through which refrigerant is supplied. For example, cold water may be supplied to the refrigerant passage <NUM>, and the first support portion <NUM> may be cooled by the cold water supplied to the first housing <NUM>.

<FIG> is another cross-sectional view of a first support portion according to an embodiment of the present disclosure.

Referring to <FIG>, the first housing <NUM> may include a refrigerant passage <NUM>, and the refrigerant passage <NUM> may be formed to surround a first bearing <NUM>. In detail, the refrigerant passage <NUM> may be formed to surround an external surface of the first bearing <NUM>, and may be provided so as to be as close to the first bearing <NUM> as possible on the external surface of the first bearing <NUM> for effective cooling.

As described above, the first housing <NUM> may include the refrigerant passage <NUM> on the external surface of the first bearing <NUM>, so that the cooling effect of the first bearing <NUM> and the rotating axis <NUM> may be improved.

In addition, it is possible to minimize a heat generation phenomenon of the first support portion <NUM> and conduction of heat generated from the second support portion <NUM> and the first support portion <NUM> to the rolling roll <NUM> through the supply of the refrigerant.

Meanwhile, there is a difference in thermal expansion amount exists between the both end portions 130b and the central portion 130a of the rolling roll <NUM>, adjacent to the first support portion <NUM> and the second support portion <NUM> due to the heat generation phenomenon of the first support portion <NUM> and the second support portion <NUM>.

According to an embodiment of the present disclosure, a difference in thermal expansion between both end portions 130b and the central portion 130a of the rolling roll <NUM> may be reduced due to the cooling effect of the first support portion <NUM>.

Summarizing the contents described above, the rolling apparatus <NUM> according to an embodiment of the present disclosure may roll the electrode sheet <NUM> at high density, and thus has an effect of manufacturing a secondary battery having improved energy density.

In addition, since both end portions 130b of a pair of rolling rolls <NUM> do not come into contact during rolling, uniform rolling may be performed regardless of a position of the electrode sheet <NUM>, so that the frequency of breakage of the electrode sheet <NUM> may be reduced, and since a period of use of the rolling roll <NUM> is also extended, operating costs may be reduced.

As set forth above, according to an embodiment of the present disclosure, in a rolling apparatus for a secondary battery electrode sheet according to an embodiment of the present disclosure, pressure applied to the electrode sheet increases during rolling, so that a secondary battery having improved energy density may be manufactured and the performance of the secondary battery may be improved.

Claim 1:
A rolling apparatus (<NUM>) for a secondary battery electrode sheet (<NUM>), comprising:
a transfer unit (<NUM>, <NUM>) transferring an electrode sheet (<NUM>) having an electrode mixture layer (<NUM>) applied to at least one surface thereof in a first direction (A);
a rolling roll (<NUM>) pressing the electrode sheet (<NUM>) in a second direction (B), intersecting the first direction (A); and
a support portion (<NUM>, <NUM>) coupled to a rotational axis (<NUM>) of the rolling roll (<NUM>) to support rotation of the rolling roll (<NUM>),
wherein the rolling roll (<NUM>) has a shape in which a central portion (130a) thereof in an axial direction protrudes further toward the electrode sheet (<NUM>) than both end portions (130b) thereof in an axial direction,
characterized in that
the rolling roll (<NUM>) is formed to have a diameter in a range of <NUM> to <NUM>,
wherein the support portion (<NUM>, <NUM>) comprises:
a first support portion (<NUM>) disposed outside the rolling roll (<NUM>) in a longitudinal direction of the rotational axis, the first support portion (<NUM>) including a first bearing (<NUM>) that is pressed in a direction in which the rolling roll (<NUM>) presses the electrode sheet (<NUM>), and a first housing (<NUM>) in which the first bearing (<NUM>) is accommodated; and
a second support portion (<NUM>) disposed outside the first support portion (<NUM>) in a longitudinal direction of the rotational axis, the second support portion (<NUM>) including a second bearing (<NUM>) that is pressed in a direction, opposite to the direction in which the first bearing (<NUM>) is pressed, and a second housing (<NUM>) in which the second bearing (<NUM>) is accommodated,
wherein the first bearing (<NUM>) comprises a four-row roller bearing.