Patent Description:
In general, unlike a primary battery that cannot be charged, a secondary battery can be charged and discharged. A low-capacity secondary battery packaged in the form of a pack comprised of one single cell is used as the power source for various portable small-sized electronic devices, such as mobile phones, camcorders, and so on. A high-capacity secondary battery in which several tens of cells are connected in a battery pack is used as the power source for motor drives, such as those in electric bicycles, electric scooters, hybrid vehicles, or electric vehicles.

Small-sized mobile devices, such as cellular phones, can be operated for a predetermined period of time using the output and capacity of a single battery, However, when a long time operation or a high power operation is required, like in an electric vehicle or a hybrid vehicle, use of a battery pack or a battery module is preferred from the view point of output or capacity, and an output voltage or current can be increased by increasing the number of battery cells included in the battery pack. Here, the battery pack requires a connection structure for forming an assembly by structurally combining a plurality of battery cells.

The present invention provides a battery pack as defined by claim <NUM>.

An embodiment provides a battery pack, which does not affect the overall outline dimension of a battery pack module even if the battery pack is inflated due to swelling in the course of assembling two or more battery cells to form the battery module.

In an embodiment, the above and other objects can be accomplished by providing a battery pack including a plurality of battery cells, each including an upper surface through which a pair of electrode terminals are protruded, a lower surface facing the upper surface, and a pair of long side surfaces and a pair of short side surfaces among surfaces connecting the upper surface and the lower surface, the long side surfaces having a relatively large area, and the short side surfaces having a relatively small area, and a cell frame that receives the battery cells, exposes the upper surfaces of the battery cells, and includes side plates for supporting the short side surfaces of the plurality of battery cells and end plates positioned at opposite ends to support the long side surfaces of the battery cells, wherein the end plates include protrusions protruding in a direction opposite to a direction in which the end plates face long side surfaces of the battery cells at the opposite ends, and a recess located between the protrusions, depressed in a direction of long side surfaces of the battery cells, and providing an extra space for swelling.

The end plates may include cylindrical supports located in the protrusions to fixedly support the battery pack to an external device, and the supports may have cut portions located near to the battery cells to have planes parallel with the long side surfaces of the battery cells.

Alternatively, the recess of the end plates may include several embossed creases located in the same direction, and a distance between each of the long side surfaces of the battery pack and the outermost one of the embossed creases is smaller than a distance between each of the long side surfaces of the battery pack and each of the protrusions.

Preferably, the protrusions of the end plates may include extending parts located to extend toward the side plates, the extending parts overlapping with regions of the side plates. In addition, the extending parts of the end plates and the regions overlapping with the side plates may be located at exterior sides of the battery cells.

The battery cells may be prismatic secondary batteries, and each of the battery cells may be provided by winding an electrode assembly including a first electrode plate, a second electrode plate and a separator positioned between the first electrode plate and the second electrode plate.

Preferably, the cell frame may accommodate the battery cells such that lower surfaces of the battery cells face a bottom side of the cell frame to upwardly expose upper surfaces of the battery cells, short side surfaces of the battery cells face side plates of the cell frame, and long side surfaces of the outermost one among the battery cells face the end plates of the cell frame. In addition, the cell frame may include a plurality of internal partitions for independently accommodating the battery cells.

Regarding advantageous effects, as described above, in the battery pack according to an embodiment of the present invention, since increased volumes of battery cells swollen when the battery cells are inflated due to swelling can be absorbed in a recess located in end plates of a cell frame, there is no change in the overall outline dimension of the battery pack.

Hereinafter, a preferred embodiment of the present invention will be described in detail.

Various embodiments of the present invention may be embodied in many different forms and should not be construed as being limited to the example embodiments set forth herein. Rather, these example embodiments of the disclosure are provided so that this disclosure will be thorough and complete and will convey inventive concepts of the disclosure to those skilled in the art.

In the accompanying drawings, sizes or thicknesses of various components are exaggerated for brevity and clarity. In addition, it will be understood that when an element A is referred to as being "connected to" an element B, the element A can be directly connected to the element B or an intervening element C may be present and the element A and the element B are indirectly connected to each other.

As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprise or include" and/or "comprising or including," when used in this specification, specify the presence of stated features, numbers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and/or groups thereof.

It will be understood that, although the terms first, second, etc. may be used herein to describe various members, elements, regions, layers and/or sections, these members, elements, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one member, element, region, layer and/or section from another. Thus, for example, a first member, a first element, a first region, a first layer and/or a first section discussed below could be termed a second member, a second element, a second region, a second layer and/or a second section without departing from the teachings of the present disclosure.

Spatially relative terms, such as "below," "beneath," "lower," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "on" or "above" the other elements or features.

<FIG> is a perspective view of a battery pack according to an embodiment of the present invention. <FIG>, <FIG> and <FIG> are a perspective view, a cross-sectional view and an exploded perspective view of a cell in the battery pack according to an embodiment of the present invention. <FIG> is a cross-sectional view of end plates of the battery pack according to an embodiment of the present invention. <FIG> is a cross-sectional view of end plates of the battery pack according to another embodiment of the present invention. <FIG> is an enlarged cross-sectional view of a portion around a protrusion of the battery pack according to an embodiment of the present invention. <FIG> illustrates views for comparison of swelling phenomena occurring to the battery pack according to an embodiment of the present invention and a conventional battery pack.

Only a first half of the battery pack is shown in <FIG>. That is to say, a cell frame configuration according to an embodiment of the present invention can be applied to not only to the first half of the battery pack but also to a second half of the battery pack.

Referring to <FIG>, the battery pack according to an embodiment of the present invention includes a plurality of battery cells <NUM> and a cell frame <NUM> around the plurality of battery cells <NUM>.

The battery cells <NUM> may include a case <NUM> and an electrode assembly <NUM> accommodated in the case <NUM>. While the illustrated battery cells <NUM> are prismatic batteries, aspects of the present invention are not limited thereto. In some cases, pouch-type batteries may be used as the battery cells <NUM>. That is to say, the battery cells <NUM> disclosed herein are just provided by way of example for a better understanding of the present invention, and the present invention does not limit the battery cell structure to that disclosed herein.

As illustrated in <FIG>, each of the battery cells <NUM> may include a case <NUM>, an electrode assembly <NUM>, a cap plate <NUM>, a first terminal <NUM> and a second terminal <NUM>.

The case <NUM> includes a conductive metal, such as aluminum, an aluminum alloy or nickel plated steel, and has a substantially hexahedral shape to have a hollow opening to allow the electrode assembly <NUM> to be inserted and placed. Since the case <NUM> and the cap plate <NUM> coupled to each other is illustrated in <FIG>, the opening is not shown. However, the opening is a portion of a top portion of the case <NUM>, which is substantially opened. Meanwhile, an interior surface of the case <NUM> is insulated so that the case <NUM> is insulated from the electrode assembly <NUM>. Here, the case <NUM> may also be referred to as a can in some cases.

In addition, the case <NUM> includes first and second long side surfaces <NUM> and <NUM> facing each other and spaced a predetermined distance apart from each other while, first and second short side surfaces <NUM> and <NUM> facing each other, spaced a predetermined distance apart from each other and connected to the first and second long side surfaces <NUM> and <NUM>, a lower surface <NUM> connecting the first and second long side surfaces <NUM> and <NUM> to the first and second short side surfaces <NUM> and <NUM> at a bottom portion, and an upper surface <NUM> connecting the first and second long side surfaces <NUM> and <NUM> to the first and second short side surfaces <NUM> and <NUM> at a top portion. Here, the upper surface <NUM> may substantially correspond to the upper surface of the cap plate <NUM>, which will later be described.

The electrode assembly <NUM> is provided by winding or laminating a stack of a first electrode plate <NUM>, a separator <NUM>, and a second electrode plate <NUM>, which includes thin plate or layers. Here, the first electrode plate <NUM> may serve as a positive electrode and the second electrode plate <NUM> may serve as a negative electrode, or vice versa.

The first electrode plate <NUM> includes a first current collector plate 121a including a metal foil or mesh made of aluminum or an aluminum alloy, a first coating portion 121b provided by coating a first electrical active material, such as a transition metal oxide, on the first current collector plate 121a, a first non-coating portion (a first uncoated portion) 121c that is not coated with the first electrical active material, and a first current collector tab 121d extending outwardly (upwardly) from the first non-coating portion 121c and electrically connected to the first terminal <NUM>. Here, the first current collector tab 121d becomes a path of current between the first electrode plate <NUM> and the first terminal <NUM>.

The second electrode plate <NUM> includes a second current collector plate 123a including a metal foil or mesh made of copper, a copper alloy, nickel or a nickel alloy, a second coating portion 123b provided by coating a second electrical active material, such as graphite or carbon, on the second current collector plate 123a, a second non-coating portion (a second uncoated portion) 123c that is not coated with the second electrical active material, and a second current collector tab 123d extending outwardly (upwardly) from the second non-coating portion 131c and electrically connected to the second terminal <NUM>. Here, the second current collector tab 123d becomes a path of current between the second electrode plate <NUM> and the second terminal <NUM>.

The separator <NUM> may be positioned between the first electrode plate <NUM> and the second electrode plate <NUM> to prevent an electrical short from occurring therebetween, and allows lithium ions to move. In addition, the separator <NUM> may include polyethylene, polypropylene, or a composite film of polyethylene and polypropylene, but the present invention does not limit the material of the separator <NUM> to those disclosed herein.

Meanwhile, a winding axis of the electrode assembly <NUM> is located to be substantially parallel or horizontal with terminal axes of the first and second terminals <NUM> and <NUM>. Here, the winding axis and the terminal axes may mean axes located in vertical directions, as shown in <FIG> and <FIG>. It will be understood that when the winding axis and terminal axes are referred to as being substantially parallel or horizontal with each other, the winding axis and terminal axes may not meet each other even if they are extended long, or may meet each other when they are extended extremely long.

In addition, as described above, the first current collector tab 121d is positioned between the electrode assembly <NUM> and the first terminal <NUM>, and the second current collector tab 123d is positioned between the electrode assembly <NUM> and the second terminal <NUM>. That is to say, the first current collector tab 121d is extended from a top end of the electrode assembly <NUM> to the first terminal <NUM> to then be connected or welded. In addition, the second current collector tab 123d is extended from the top end of the electrode assembly <NUM> to the second terminal <NUM> to then be connected or welded.

As described above, the first current collector tab 121d may be the first non-coating portion 121c of the first electrode plate <NUM>, which is not coated with the first active material, or a separate member connected to the first non-coating portion 121c. Here, a material of the separate member may be one selected from the group consisting of aluminum, an aluminum alloy, nickel, a nickel alloy, copper, a copper alloy, and equivalents thereof.

In addition, the second current collector tab 123d may be the second non-coating portion 123c of the second electrode plate <NUM>, which is not coated with the second active material, or a separate member connected to the second non-coating portion 123c. Here, a material of the separate member may be one selected from the group consisting of nickel, a nickel alloy, copper, a copper alloy, aluminum, an aluminum alloy, and equivalents thereof.

As described above, since the winding axis of the electrode assembly <NUM> is located to be substantially parallel or horizontal with the terminal axes of the first and second terminals <NUM> and <NUM>, a direction in which an electrolyte is injected may also be substantially parallel or horizontal with the winding axis. Therefore, the electrode assembly <NUM> may demonstrate excellent electrolyte wettability during electrolyte injection, and internal gases of the electrode assembly <NUM> may rapidly move toward a safety vent <NUM>, thereby allowing the safety vent <NUM> to operate quickly.

In addition, since the first and second current collector tabs 121d and 123d (non-coating portions or separate members) of the electrode assembly <NUM> are directly electrically connected to the first and second terminals <NUM> and <NUM>, respectively, to shorten electrical paths, internal resistance of each of the battery cells <NUM> can be reduced and the number of components can also be reduced.

The electrode assembly <NUM> can be accommodated in the case <NUM> with an electrolyte. The electrolyte may include a lithium salt, such as, LiPF<NUM> or LiBF<NUM>, dissolved in an organic solvent, such as EC, PC, DEC, EMC, or DMC. In addition, the electrolyte may be in a liquid, solid or gel phase.

The cap plate <NUM> is substantially shaped of a rectangle having a length (equal to a length of each of long side surfaces <NUM>) and a width (equal to a width of each of short side surfaces <NUM>, and is coupled to the case <NUM>. That is to say, the cap plate <NUM> seals the opening of the case <NUM> and may be located using the same material with the case <NUM>. The cap plate <NUM> may be coupled to the case <NUM> by, for example, laser and/or ultrasonic welding. Here, the cap plate <NUM> may also be referred to as a cap assembly in some cases.

The cap plate <NUM> includes a plug <NUM> closing an electrolyte injection hole <NUM> and a safety vent <NUM> closing a vent hole <NUM>. In addition, the safety vent <NUM> may further include a notch 136a configured to be easily opened at a preset pressure.

In addition, the cap plate <NUM> further includes a fuse part <NUM> electrically connected to the first current collector tab 121d of the electrode assembly <NUM>, and a terminal fixing part <NUM> constraining the first terminal <NUM>. That is to say, the cap plate <NUM> includes at least one (e.g., two in the illustrated embodiment) fuse part <NUM> downwardly extending a predetermined length and protruding from the cap plate <NUM>, and at least one (e.g., two in the illustrated embodiment) terminal fixing part <NUM> upwardly extending a predetermined length and protruding from the cap plate <NUM>.

Here, the fuse parts <NUM> are located at opposite sides in a widthwise direction of the cap plate <NUM> (i.e., in a y-y direction), and the terminal fixing parts <NUM> are located at opposite sides in a lengthwise direction of the cap plate <NUM> (i.e., in an x-x direction), respectively.

The first terminal <NUM> includes a first terminal plate <NUM> positioned on the upper surface of the cap plate <NUM>, a first insulation plate <NUM> positioned on a lower surface of the cap plate <NUM>, and a first current collector plate <NUM> positioned on a lower surface of the first insulation plate <NUM>.

The first terminal plate <NUM> is shaped of a substantially solid hexahedron and is fixed to the upper surface of the cap plate <NUM> through the terminal fixing part <NUM>. To this end, the terminal fixing parts <NUM> are located at opposite sides of the first terminal plate <NUM>, for example, in the lengthwise direction of the cap plate <NUM> (i.e., in the x-x direction) to constrain left and right side surfaces of the first terminal plate <NUM>. In addition, the terminal fixing part <NUM> is laser or ultrasonic welded to the first terminal plate <NUM>, thereby fixing the terminal fixing part <NUM> and the first terminal plate <NUM> to each other.

The first insulation plate <NUM> has a substantially hexahedral shape and is coupled to the fuse parts <NUM> downwardly extending and/or protruding from the lower surface of the cap plate <NUM>. To this end, fuse penetration holes 142a are located in the first insulation plate <NUM>. That is to say, the fuse parts <NUM> are located in the widthwise direction of the cap plate <NUM> (that is, in the y-y direction), and the fuse penetration holes 142a are located at locations of the first insulation plate <NUM> corresponding to the fuse parts <NUM>. The fuse parts <NUM> are coupled to the fuse penetration holes 142a. Here, fuse penetration cutting grooves, instead of the fuse penetration holes 142a, may be located.

The first current collector plate <NUM> has a substantially hexahedral shape and is coupled to the fuse parts <NUM>. To this end, fuse penetration holes 143a are located in the first current collector plate <NUM> in the widthwise direction of the cap plate <NUM> (i.e., in the y-y direction). The fuse parts <NUM> are fixed to the fuse penetration holes 143a of the first current collector plate <NUM> by, for example, welding, caulking or riveting while being coupled to the fuse penetration holes 143a. Here, fuse penetration cutting grooves, instead of the fuse penetration holes 143a, may be located.

In addition, the first current collector tab 121d extending from the electrode assembly <NUM> is connected to the first current collector plate <NUM>. That is to say, the first current collector tab 121d is welded to the first current collector plate <NUM> by laser or ultrasonic welding. Here, since the first current collector plate <NUM> and the first current collector tab 121d are both made of aluminum or an aluminum alloy, they can be easily electrically/mechanically connected to each other.

In this way, the first current collector tab 121d of the electrode assembly <NUM>, the cap plate <NUM> (including the case <NUM>) and the first terminal <NUM> may have the same polarity. That is to say, since the first current collector tab 121d of the electrode assembly <NUM>, the first current collector plate <NUM> of the first terminal <NUM>, the fuse parts <NUM> of the cap plate <NUM>, the cap plate <NUM>, and the first terminal plate <NUM> of the first terminal <NUM> are all electrically connected to one another, they will have the same polarity.

As described above, not only the cap plate <NUM> and the fuse parts <NUM> but also the first current collector plate <NUM> and the first terminal plate <NUM> may be made of aluminum or an aluminum alloy.

When the battery pack <NUM> is externally short-circuited, short-circuit current may flow from the electrode assembly <NUM> through the first current collector tab 121d, the first current collector plate <NUM> of the first terminal <NUM>, the fuse parts <NUM> of the cap plate <NUM>, the cap plate <NUM> and the first terminal plate <NUM> of the first terminal <NUM>. Here, since the fuse parts <NUM> have relatively small sectional areas, the fuse parts <NUM> located in the cap plate <NUM> may be fused and broken, thereby securing the safety of the battery pack <NUM>. Moreover, since the fuse parts <NUM> are mostly coupled to the fuse penetration holes 142a of the first insulation plate <NUM> so as not to be exposed, flame or arc generated when the fuse parts <NUM> are fused/broken may not affect exterior sides of the first insulation plate <NUM>. Therefore, even when the fuse parts <NUM> are fused and broken, the internal space of the battery pack <NUM> can be stably maintained.

In addition, when the battery pack <NUM> is overcharged, overcharge current may be supplied to the electrode assembly <NUM> through the first terminal plate <NUM> of the first terminal <NUM>, the cap plate <NUM>, the fuse parts <NUM> of the cap plate <NUM>, the first current collector plate <NUM> and the first current collector tab 121d, so that the fuse parts <NUM> located in the cap plate <NUM> are fused to then be broken, thereby securing the safety of the battery pack <NUM>.

The second terminal <NUM> includes a second terminal plate <NUM> positioned on the upper surface of the cap plate <NUM>, a second insulation plate <NUM> positioned on the lower surface of the cap plate <NUM>, a second current collector plate <NUM> positioned on a lower surface of the second insulation plate <NUM>, and a current collection pillar <NUM> penetrating the cap plate <NUM> from the second current collector plate <NUM> to then be fixed to the second terminal plate <NUM>. In addition, the second terminal <NUM> includes a second terminal plate <NUM>, a current collection pillar <NUM>, and an upper insulation plate <NUM> interposed between the cap plate <NUM> and the second terminal <NUM>. Moreover, the second terminal <NUM> includes a second current collector plate <NUM>, a current collection pillar <NUM>, and a seal gasket <NUM> interposed between the cap plate <NUM> and the second terminal <NUM>.

In practice, the second current collector plate <NUM> and the second current collection pillar <NUM> are integrally located, and the second current collector tab 123d is connected to the second current collector plate <NUM>. Since the second current collector plate <NUM> and the second current collection pillar <NUM> are made of copper or a copper ally, the second current collector tab 123d made of copper, a copper alloy, nickel or a nickel alloy, may be easily electrically/mechanically connected to the second current collector plate <NUM>.

The second terminal plate <NUM> is also positioned on the cap plate <NUM> and has a hole 151a. In addition, the current collection pillar <NUM> is coupled to the hole 151a and then welded. A boundary region between the upwardly exposed current collection pillar <NUM> and the second terminal plate <NUM> is fused to each other by supplying, for example, laser beams, to the boundary region, followed by cooling, thereby achieving welding.

Next, the cell frame <NUM> is located to cover the upper surface <NUM>, the lower surface <NUM>, the first short side surface <NUM> and the second short side surface <NUM> of the battery cells <NUM>. Here, the battery cells <NUM> are accommodated in the cell frame <NUM> while the upper surface <NUM> is upwardly exposed.

That is to say, the cell frame <NUM> is configured to cover and accommodate the lower surface <NUM>, the first short side surface <NUM> and the second short side surface <NUM> of the battery pack. In detail, the cell frame <NUM> include a pair of side plates <NUM> for supporting the first and second short side surfaces <NUM> and <NUM> of the battery cells <NUM>, and a pair of end plates <NUM> for supporting the first and second long side surfaces <NUM> and <NUM> of the battery cells <NUM>. Only a first half of the end plates <NUM> is shown in <FIG>.

Referring to <FIG>, the lower surface <NUM> of the battery cells <NUM> comes into contact with a lower surface of the cell frame <NUM> and the upper surface thereof is exposed to the outside through the opening of the cell frame <NUM>. Accordingly, the battery cells <NUM> can be easily and rapidly inserted into or extracted from the cell frame <NUM>. The end plates <NUM> of the cell frame <NUM> are located to have substantially planar plate shapes and are coupled to opposite sides of the side plates <NUM> of the cell frame <NUM> to support the battery cells <NUM> at once. The end plates <NUM> and the side plates <NUM> may be fastened by, for example, welding, such as laser welding, or bolt engagement, but aspects of the present invention are not limited thereto.

In addition, as shown in <FIG>, when viewed from the top surface <NUM> of the battery cells <NUM>, the end plates <NUM> further include substantially pillar-shaped protrusions <NUM> protruding in a direction opposite to a direction in which the end plates <NUM> face the long side surfaces <NUM> and <NUM> of the battery cells <NUM>, that is, in an outward direction of the cell frame <NUM>. The protrusions <NUM> may have circular or rectangular sectional shapes. As shown in <FIG>, the protrusions <NUM> may be shaped of rectangles such that first surfaces thereof facing the battery cells <NUM> are opened. Alternatively, the protrusions <NUM> may have various sectional shapes in addition to those disclosed herein.

In addition, the end plates <NUM> further include a recess <NUM> located between the opposite protrusions <NUM> and depressed in a direction of the long side surfaces <NUM> and <NUM> of the battery cells <NUM>. The recess <NUM> is depressed toward the battery cells <NUM> in view of the outermost surfaces of the protrusions <NUM>, so that it has an inverted U-shaped configuration as a whole, as shown in <FIG>. The recess <NUM> provides an extra space for swelling of the battery cells <NUM>.

Referring to <FIG>, since the recess <NUM> is inwardly depressed a predetermined distance L1 from the outer surface of the battery pack, the battery cells <NUM> may have a swelling space corresponding to the distance L1 in the direction of their long side surfaces. That is to say, in the battery pack according to the embodiment of the present invention, since there is a swelling space as much as the distance L1 in the direction of the long side surfaces of the battery cells <NUM>, the outline dimension of the battery pack module is not affected even if the battery cells <NUM> are inflated due to swelling.

Referring to <FIG>, the end plates <NUM> include supports <NUM> centrally located at the protrusions <NUM> to fix the battery pack to an external device.

The supports <NUM> may include bolts having screws located at their lower portions, and are preferably shaped of a cylinder having a predetermined diameter to maintain rigidity of the end plates <NUM>.

Referring back to <FIG>, the supports <NUM> may have cut regions near to the battery cells <NUM> to have planes parallel with the long side surfaces of the battery cells <NUM>. Accordingly, the cross sections of the supports <NUM> nearest to the battery cells <NUM> may become planarly cut surfaces, and the supports <NUM> may become farther from the long side surfaces of the battery cells <NUM> than in a case where the supports <NUM> have circular cross sections without cut regions, thereby providing an extra distance L2, as shown in <FIG>.

Accordingly, even if swelling occurs to the battery cells <NUM>, extra spaces as much as the distance L2 are created at ends of the long side surfaces of the battery cells <NUM>.

While the supports <NUM> shaped of solid cylinders are illustrated, they may be shaped of, for example, hollow pipes.

Referring back to <FIG>, the recess <NUM> of the end plates <NUM> may include several embossed creases located in the same direction. The creases are provided for supporting lateral rigidity of the end plates <NUM>, and the embossed creases as well as the protrusions <NUM> of the end plates <NUM> and the supports <NUM> may have a predetermined thickness to function to support the end plates <NUM>. Here, the embossed creases are preferably located in a direction perpendicular to the protrusions <NUM> and the supports <NUM>. In addition, a distance between the outline dimension of the embossed creases of the recess <NUM> or each of the long side surface of the battery pack and the outermost one of the embossed creases is preferably smaller than a distance between the outline dimension of the protrusions <NUM> of the end plates <NUM> or each of the long side surfaces of the battery pack and the outmost one of the protrusions <NUM> of the end plates <NUM>, and a difference in the distance is preferably as much as the distance L1 that is an extra space for swelling, as shown in <FIG>.

Referring to <FIG>, the protrusions <NUM> of the end plates <NUM> may include extending parts located to extend toward the side plates <NUM>. The extending parts may overlap with some regions of the side plates, preferably ends of the side plates, to then be coupled thereto. The extending parts of the protrusions <NUM> may be coupled to the ends of the side plates by bolt engagement or welding, such as laser welding.

In the embodiment of the present invention, as shown in <FIG>, the extending parts of the protrusions <NUM> and the ends of the side plates <NUM> overlap each other to then be coupled to each other at exterior sides of the protrusions <NUM>.

In the embodiment of the present invention, as shown in <FIG>, the extending parts of the protrusions <NUM> and the ends of the side plates <NUM> overlap each other to then be coupled to each other at exterior sides of the shorter side surfaces of the battery cells <NUM>.

The cell frame <NUM> may further include internal partitions <NUM> for separately fixing battery cells <NUM> to independently accommodate the battery cells <NUM>.

<FIG> illustrates views for comparison of swelling phenomena occurring to the battery pack according to an embodiment of the present invention and a conventional battery pack.

<FIG> illustrates a distorted state of the conventional battery pack when swelling occurs to battery cells. Referring to <FIG>, in the conventional battery pack, in which a recess is not located in end plates, if swelling occurs to the battery cells, the end plates are pushed out as much as swollen volumes of the battery cells. Then, the outline dimension of the conventional battery pack may increase as the swollen volumes.

<FIG> illustrates a distorted state of the battery pack according to an embodiment of the present invention when swelling occurs to battery cells. Referring to <FIG>, even if the end plates are pushed out as much as swollen volumes of the battery cells as the battery pack is inflated due to swelling occurring to the battery cells, the volume of the end plates pushed out may be taken in the extra space provided in the end plates. Therefore, there is no change in the overall outline dimension of the battery pack.

As described above, in the battery pack according to the embodiment of the present invention, even if the battery cells are inflated due to swelling, the end plates are not pushed out by the extra space provided therein, so that the outline dimension of the battery pack is not affected, thereby allowing the battery pack to be used in a secured manner.

<FIG> is an exploded perspective view of a cell in the battery pack according to another embodiment of the present invention. That is to say, <FIG> illustrates a pouch type battery as a battery cell <NUM>.

The battery cell <NUM> may include an electrode assembly <NUM> and a case (pouch) <NUM> accommodating the electrode assembly <NUM>. The electrode assembly <NUM> is provided by winding or laminating a stack of a first electrode plate <NUM>, a separator <NUM>, and a second electrode plate <NUM>. Here, the first electrode plate <NUM> may be a positive electrode and the second electrode plate <NUM> may be a negative electrode, or vice versa.

When the first electrode plate <NUM> is a positive electrode, it is produced by coating a first active material layer on both surfaces of a first current collector made of a highly conductive metal plate, for example, an aluminum (Al) foil. A first electrode tab <NUM> is located at a first non-coating portion where the first active material layer of the first electrode plate <NUM> is not coated. One end of the first electrode tab <NUM> is electrically connected to the first non-coating portion and the other end thereof is drawn out from the case <NUM>. In addition, an insulation tape <NUM> is attached to a region of the first electrode tab <NUM> contacting the case <NUM>.

When the second electrode plate <NUM> is a negative electrode, it is produced by coating a second active material layer on both surfaces of a second current collector made of a conductive metal plate, for example, a copper (Cu) or nickel (Ni) foil. A second electrode tab <NUM> is located at a second non-coating portion where the second active material layer of the second electrode plate <NUM> is not coated. One end of the second electrode tab <NUM> is electrically connected to the second non-coating portion and the other end thereof is drawn out from the case <NUM>. In addition, an insulation tape <NUM> is attached to a region of the second electrode tab <NUM> contacting the case <NUM>.

The separator <NUM> is positioned between the first electrode plate <NUM> and the second electrode plate <NUM> and prevents a short circuit between the first and second electrode plates <NUM> and <NUM>.

The case <NUM> includes an upper case <NUM> and a lower case <NUM>, which are produced by folding one side of an integrally shaped parallelepiped pouch layer midway in a lengthwise direction. A groove <NUM>, in which the electrode assembly <NUM> is to be accommodated, is provided in the lower case <NUM> by pressing. In addition, opposite-side sealing parts <NUM> and one-side sealing part 322b are provided in the lower case <NUM> to be sealed with the upper case <NUM> along three sides of the groove <NUM>, except for one side in which the upper case <NUM> and the lower case <NUM> are in contact with each other.

After the electrode assembly <NUM> is accommodated in the groove <NUM> of the lower case <NUM> , the case <NUM> is sealed by thermally fusing the sealing parts 322a and the sealing part 322b in a state in which the upper case <NUM> and the lower case <NUM> are brought into close contact with each other. Then, the side-surface sealing part 322a, except for the sealing parts 322b, from which the first and second electrode tabs <NUM> and <NUM> of the battery cell <NUM> protrude, is bent toward side surfaces of the lower case <NUM>.

Meanwhile, the battery cell <NUM> includes a top surface 300a from which the first and second electrode tabs <NUM> and <NUM> are drawn out, a bottom surface 300b facing the top surface 300a, and a pair of first and second long side surfaces 300c and 300d having a relatively large area and a pair of first and second short side surfaces 300e and 300f having a relatively small area, among surfaces connecting the top surface 300a and the bottom surface 300b.

The cell frame <NUM> may be provided to cover the top surface 300a, the bottom surface 300b, the first short side surface 300e and the second short side surface 300f of the battery cell <NUM>. The battery cell <NUM> may be accommodated in the cell frame <NUM> while the top surface 300a is upwardly exposed. That is to say, the cell frame <NUM> may be configured to accommodate the battery cell <NUM> while enclosing the bottom surface 300b, the first short side surface 300e and the second short side surface 300f. In detail, the cell frame <NUM> may include side plates <NUM> for supporting the first and second short side surfaces 300e and 330f of a plurality of battery cells <NUM> and end plates <NUM> for supporting the first and second long side surfaces 300c and 300d of the battery cells <NUM>. Since organic connection relationships between the other battery cells and the cell frame are substantially the same as described above, additional descriptions will not be given.

Although the foregoing embodiments have been described to practice the battery pack of embodiments of the present invention, these embodiments are set forth for illustrative purposes and do not serve to limit the invention which is defined by the claims. Those skilled in the art will readily appreciate that many modifications and variations can be made, without departing from the scope of the invention as defined in the appended claims, and such modifications and variations are encompassed within the scope of the present invention.

Claim 1:
A battery pack comprising: a plurality of battery cells (<NUM>, <NUM>), each including an upper surface (<NUM>, 300a) through which a pair of electrode terminals (<NUM>, <NUM>) are protruded, a lower surface (<NUM>, 300b) facing the upper surface, and a pair of long side surfaces (<NUM>, <NUM>, 300c, 300d) and a pair of short side surfaces (<NUM>, <NUM>, 300e, 300f) among surfaces connecting the upper surface and the lower surface, the long side surfaces having a relatively large area, and the short side surfaces having a relatively small area; and a cell frame (<NUM>) that receives the battery cells (<NUM>, <NUM>), exposes the upper surfaces (<NUM>, 300a) of the battery cells, and includes side plates (<NUM>) for supporting the short side surfaces (<NUM>, <NUM>, 300e, 300f) of the plurality of battery cells and end plates (<NUM>) positioned at opposite ends to support the long side surfaces (<NUM>, <NUM>, 300c, 300d) of the battery cells, characterised in that the end plates (<NUM>) include protrusions (<NUM>) protruding in a direction opposite to a direction in which the end plates (<NUM>) face long side surfaces (<NUM>, <NUM>, 300c, 300d) of the battery cells at the opposite ends; and a recess (<NUM>) located between the protrusions (<NUM>), depressed in a direction of long side surfaces (<NUM>, <NUM>, 300c, 300d) of the battery cells, and providing an extra space for swelling.