Patent Description:
The present invention relates to a secondary battery, and more particularly to a pouch-shaped secondary battery having an electrode assembly mounted in a pouch-shaped battery case made of a laminate sheet and a battery module including the same.

In general, secondary batteries are batteries that can be charged and discharged, unlike primary batteries, which cannot be charged. Such secondary batteries have been widely used in electronic devices, such as cellular phones, laptop computers, and camcorders, or electric vehicles (EVs).

Among the secondary batteries, increase in the use of a lithium secondary battery has been rapid increasingly used, since the capacity of the lithium secondary battery is larger than the capacity of a nickel-cadmium battery or a nickel-hydride battery, which is mainly used as a power source for electronic devices, and the energy density of the lithium secondary battery per unit weight is high.

Such a lithium secondary battery mainly uses a lithium-based oxide and a carbon material as a positive electrode active material and a negative electrode active material, respectively. The lithium ion secondary battery is configured to have a structure in which a positive electrode sheet, to which the positive electrode active material is applied, and a negative electrode sheet, to which the negative electrode active material is applied, are disposed in the state in which a separator is interposed therebetween to constitute an electrode assembly and in which the electrode assembly is received in a sheathing member, i.e. a battery case, together with an electrolytic solution in a sealed state.

Depending on the shape of the battery case, the lithium secondary battery may be classified as a can-shaped secondary battery, configured such that the electrode assembly is mounted in a metal can, or a pouch-shaped secondary battery, configured such that the electrode assembly is mounted in a pouch made of an aluminum laminate sheet.

Meanwhile, the pouch-shaped secondary battery is classified as a unidirectional battery, configured such that electrode leads connected to positive electrode and negative electrode tabs of the electrode assembly are disposed at one side of the battery, or a bidirectional battery, configured such that electrode leads connected to positive electrode and negative electrode tabs of the electrode assembly are disposed at opposite sides of the battery.

In general, the pouch-shaped secondary battery includes an electrode assembly, a pouch-shaped case configured to receive the electrode assembly in a sealed state, and electrode leads extending from the electrode assembly so as to be exposed out of the pouch-shaped case.

In the pouch-shaped secondary battery described above, however, a large amount of gas is generated due to the decomposition of an electrolyte when the lifespan of the secondary battery expires, the secondary battery is overcharged, the secondary battery is exposed to high temperatures, or an internal short circuit occurs in the secondary battery, whereby the pouch-shaped case expands, i.e. a swelling phenomenon occurs. The swelling phenomenon, in which the middle portion of the pouch-shaped case swells due to gas that is generated in the pouch-shaped case, causes the deformation of the battery. As a result, a short circuit occurs in the battery. In severe cases, high pressure may be generated in the sealed case, whereby the electrolyte may be further decomposed, which may result in the explosion of the battery.

In order to solve the above problem, <CIT> and <CIT> disclose various technologies capable of dealing with the swelling phenomenon. Further solutions are also provided by <CIT>, <CIT> and <CIT>.

However, the conventional art, including the above Korean patent application publications, is configured to have a structure in which the interior space of a case is expanded in order to collect gas. As a result, the overall size of a battery is increased. In addition, since the expanded space is empty, the expanded space is weakly resistant to external force, whereby the expanded space may be easily deformed. In order to solve this problem, therefore, it is necessary to install an additional structure in the space in order to increase the rigidity of the space, which is another problem.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a pouch-shaped battery case having a hidden-type gas pocket, wherein the gas pocket is configured to be unfolded or expanded, when gas is generated, in order to form a gas reception space, whereby it is possible to reduce the extent of swelling of a battery when the gas is generated, and wherein the gas pocket is configured so as not to occupy any space in a normal state and to be unfolded only when the gas is generated in order to form the gas reception space, whereby it is possible to improve the efficiency of utilization of space in the battery, a pouch-shaped secondary battery including the same, and a battery module including the same.

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a pouch-shaped secondary battery including an electrode assembly and a pouch-shaped case configured to receive the electrode assembly, wherein the pouch-shaped case has therein a gas pocket configured such that at least a portion of the gas pocket is maintained in a folded state and such that, when gas is generated in the pouch-shaped case, the gas pocket is unfolded to form a space configured to collect the gas.

Here, the gas pocket may be formed at a portion of the pouch-shaped case that is folded in order to cover the electrode assembly at a perimeter portion of the pouch-shaped case.

The pouch-shaped case is configured to have a quadrangular planar structure, and in the case in which a perimetric surface of this quadrangular plane includes a single surface that is folded and three surfaces that are attached by sealing, the gas pocket is formed at the single surface that is folded.

In addition, the gas pocket may be formed at a portion of the pouch-shaped case that is attached by sealing at the perimeter portion of the pouch-shaped case.

In addition, the gas pocket may be formed at at least one of opposite side surfaces of the pouch-shaped case.

The pouch-shaped case includes a case main body, in which the electrode assembly is mounted, and the gas pocket formed at one side of the case main body, and the gas pocket is configured to have a structure in which the gas pocket is bent from the case main body and is then in tight contact with the case main body.

At this time, the gas pocket may be configured to have a structure in which the gas pocket is bent multiple times and is then in tight contact with the case main body.

The gas pocket may be configured to have a structure in which the gas pocket is bent so as to have a bellows structure and is then in tight contact with the case main body.

In accordance with another aspect of the present invention, there is provided a pouch-shaped battery case including a case main body, in which an electrode assembly is mounted, and a gas pocket formed at at least one side of the case main body, wherein the gas pocket is configured such that the gas pocket is maintained in a folded state and such that, when gas is generated from the electrode assembly, the gas pocket is unfolded to form a space configured to collect the gas.

It is preferable that the gas pocket is configured to have a structure in which the gas pocket is bent from the case main body and is then in tight contact with the case main body.

In accordance with a further aspect of the present invention, there is provided a battery module including one or more pouch-shaped secondary batteries described above.

The principal technical solutions described above will be more concretely and definitely disclosed with reference to the following description of "best mode" and the accompanying drawings. In addition to the principal technical solutions, various other technical solutions according to the present invention will be further provided and described.

A pouch-shaped battery case having a hidden-type gas pocket according to the present invention, a pouch-shaped secondary battery including the same, and a battery module including the same have effects in that, when gas is generated from an electrode assembly, the gas pocket, which is maintained in a folded state, is unfolded or expanded to form a gas reception space, whereby it is possible to reduce the extent of swelling of the battery case when the gas is generated, and in particular, the gas pocket is configured so as to occupy little space in a normal state and to be unfolded to form the gas reception space only when the gas is generated, whereby it is possible to improve the efficiency of utilization of space in the battery.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

<FIG> are views showing a pouch-shaped secondary battery having a hidden-type gas pocket according to a first embodiment of the present invention, wherein <FIG> is a perspective view, <FIG> is a sectional view taken along line A-A of <FIG>, <FIG> is front views showing the operation of the gas pocket, and <FIG> is sectional views taken along lines B-B, C-C, and D-D of <FIG>.

As shown in <FIG>, the pouch-shaped secondary battery having the hidden-type gas pocket according to the first embodiment of the present invention includes an electrode assembly <NUM> and a pouch-shaped case <NUM> configured to receive the electrode assembly <NUM>. In addition, the secondary battery is configured such that electrode leads <NUM> are exposed out of the pouch-shaped case <NUM>.

Here, the electrode assembly <NUM> is a power-generating element configured to have a structure including a positive electrode, a negative electrode, and a separator interposed between the two electrodes. The electrode assembly <NUM> may be constructed using a well-known electrode assembly <NUM>, and therefore a detailed description thereof will be omitted.

The pouch-shaped case <NUM> may be made of a laminate sheet configured to cover the outside of the electrode assembly <NUM> in a sealed state. Preferably, the laminate sheet is made of a metal material, such as aluminum.

The structure in which the electrode assembly <NUM> is sealed using the pouch-shaped case <NUM> may be variously constructed. In this embodiment, the pouch-shaped case <NUM> has a quadrangular sealing structure, since the electrode assembly <NUM> generally has a quadrangular planar structure.

This pouch-shaped case <NUM> is configured to have a structure in which an approximately middle portion thereof is folded, the electrode assembly <NUM> is located therebetween, and the other open three perimetric surfaces thereof are sealed except for the folded portion. Consequently, the pouch-shaped case <NUM> covers the upper surface and the lower surface of the electrode assembly <NUM> in the state in which the electrode assembly <NUM> is located therein, and the four perimetric surfaces of the pouch-shaped case, which constitute a quadrangular plane, include a single surface <NUM> that is folded (hereinafter, also referred to as a 'folded surface') and three surfaces <NUM> and <NUM> that are attached by sealing (hereinafter, also referred to as 'sealed surfaces').

Here, the sealed surfaces <NUM> and <NUM> may be portions that are sealed by adhering the overlapping portions of the laminate sheet constituting the pouch-shaped case <NUM> closely to each other by thermal welding.

In particular, a gas pocket <NUM> configured to collect gas generated from the electrode assembly <NUM> due to various causes is provided at the folded surface <NUM> of the pouch-shaped case <NUM>. The gas pocket <NUM> will be described hereinafter in detail with reference to <FIG>.

Meanwhile, <FIG> illustrates the structure in which the electrode leads <NUM> are installed at opposite ends of the pouch-shaped case <NUM> so as to be exposed. However, the direction in which the electrode leads <NUM> are exposed and the number of electrode leads <NUM> may be variously changed depending on the embodiment conditions. For example, both the electrode leads <NUM> may be exposed at one end of the pouch-shaped case <NUM>.

Now, the gas pocket <NUM> will be described below in detail with reference to <FIG>.

In this embodiment, the gas pocket <NUM> is provided at the folded surface <NUM> of the pouch-shaped case <NUM>. The gas pocket <NUM> is configured such that the gas pocket <NUM> is maintained in a folded state at the side surface of the pouch-shaped case <NUM> and such that, when gas is generated in the pouch-shaped case <NUM>, the gas pocket <NUM> is unfolded to form a space configured to collect the gas.

Referring to <FIG> and the like, the folded structure of the gas pocket <NUM> is configured to have a structure in which the gas pocket <NUM> is provided at the folded surface <NUM> of the pouch-shaped case <NUM> connected to a case main body <NUM>, in which the electrode assembly <NUM> is mounted, in which the gas pocket <NUM> is formed so as to be bent multiple times, like a rolled structure, in the state in which the folded surface <NUM> is in tight contact in a double-folded state, and in which the gas pocket <NUM> is in tight contact with the side surface of the case main body <NUM> in this state.

Referring to the figures showing the present embodiment, the gas pocket <NUM> is configured to have a structure in which the gas pocket <NUM> is bent two or three times from the middle portion of the side surface of the case main body <NUM> and is then in tight contact with the side surface of the case main body <NUM>.

For reference, in all the figures showing the embodiment of the present invention, the folded structure of the gas pocket <NUM> is somewhat widened. However, the gas pocket <NUM> is shown as described above in order to clearly show the folded structure thereof. Consequently, it is desirable to understand that the folded portions of the gas pocket <NUM> are assembled in the state of being in tight contact with each other or with the case main body <NUM>.

The gas pocket <NUM> may be configured such that the pouch-shaped case <NUM> is bent in the state of being simply in tight contact in a double-folded structure and is then in tight contact with the side surface of the case main body <NUM>. As needed, however, the overlapping portions, among the portions constituting the gas pocket <NUM>, may be sealed at low strength, and may then be brought into tight contact with the side surface of the case main body <NUM>. At this time, the sealing strength of the gas pocket <NUM> may be lower than the sealing strength of the other three sealed surfaces <NUM> and <NUM> by a predetermined level such that, when gas is generated in the pouch-shaped case, the sealed portion of the gas pocket <NUM> is widened to collect the gas.

The process of collecting the gas generated in the pouch-shaped case using the gas pocket <NUM> will be described with reference to <FIG> and <FIG>.

<FIG> and <FIG> show the state of the gas pocket <NUM> in the normal state, i.e. when no gas is generated. The gas pocket <NUM> is in tight contact with the side surface of the case main body <NUM> in an initially assembled state, i.e. in a folded state. At this time, the gas pocket <NUM> occupies only the external volume corresponding to the size of the laminate sheet that is bent multiple times and is then in tight contact, whereby the overall size of the battery is scarcely increased.

When gas is generated in the battery in the state in which the gas pocket <NUM> is folded as described above, as shown in <FIG> and <FIG>, the gas is introduced into the gas pocket <NUM>, whereby the folded gas pocket <NUM> starts to be unfolded. In the figures, the state in which the gas pocket <NUM> is unfolded in a straight line is illustrated for the sake of convenience. However, the gas pocket <NUM> may be unfolded in various shapes depending on several conditions. For example, the gas pocket <NUM> may expand while being unfolded from the entrance thereof, or the bent portion of the gas pocket <NUM> may be unfolded later.

Subsequently, when gas is continuously generated in the battery, the gas pocket <NUM> continuously swells. When the gas pocket <NUM> fully swells, as shown in <FIG> and <FIG>, the gas pocket <NUM> expands at the side surface of the battery to form a maximum gas collection space S.

The maximum gas collection space S in the gas pocket <NUM> may be appropriately set depending on embodiment conditions. By the provision of the gas pocket <NUM>, it is possible to minimize the deformation of the remaining portion of the battery, excluding the portion of the battery at which the gas pocket is located, when gas is generated in the battery. In particular, it is possible to sufficiently secure the gas collection space, whereby it is possible to prevent explosion of the battery.

Hereinafter, various embodiments of the gas pocket according to the present invention will be described. For reference, components of the following embodiments that are identical or similar to the components of the first embodiment are denoted by the same reference numerals, a duplicate description thereof will be omitted if possible, and a description will be given based on components of the following embodiments that are different from the components of the first embodiment.

<FIG> and <FIG> are views showing a pouch-shaped secondary battery having a hidden-type gas pocket according to a second embodiment of the present invention, wherein <FIG> is a cross-sectional view and <FIG> is sectional views of principal parts showing the operation of the gas pocket.

In the first embodiment of the present invention previously described, the gas pocket <NUM> is provided only at the folded portion of the pouch-shaped case <NUM>, i.e. the folded surface <NUM>. In the second embodiment of the present invention, however, the construction in which the gas pocket <NUM> may also be formed at the sealed portion of the pouch-shaped case <NUM>, i.e. the sealed surface <NUM>, is shown.

That is, referring to <FIG> and <FIG>, the gas pocket <NUM> according to the second embodiment of the present invention may be provided at opposite sides of the pouch-shaped case <NUM>. At this time, since the one side surface of the pouch-shaped case <NUM> is the folded surface <NUM> and the other side surface of the pouch-shaped case <NUM> is the sealed surface <NUM>, a gas pocket <NUM> at the folded surface <NUM> may be configured as in the first embodiment, which was previously described, and a gas pocket <NUM> at the sealed surface <NUM> may be configured such that only the ends of the double-folded portions of the gas pocket are joined by sealing and the remainder of the double-folded portions of the gas pocket are folded in the state of being in tight contact with each other in order to constitute the gas pocket <NUM>.

Here, it may be considered that the sealed surface <NUM>, at which the gas pocket <NUM> is formed, is formed so as to have a smaller width of the sealing attachment surface than the other sealed surfaces <NUM> (see <FIG>), at which no gas pocket <NUM> is formed. This serves to enlarge the gas collection space of the gas pocket <NUM> while the sealing area thereof is minimized.

<FIG> sequentially show the folded and assembled state of the gas pocket <NUM>, the state in which the gas pocket <NUM> starts to be unfolded, and the maximum gas collection state of the gas pocket <NUM>.

In the structure in which the gas pocket <NUM> is also formed at the sealed surface <NUM> of the pouch-shaped case <NUM>, as described above, the gas pocket <NUM> may not be formed at the folded surface <NUM> of the pouch-shaped case <NUM>, and the gas pocket <NUM> may be formed at only the sealed surface <NUM> of the pouch-shaped case <NUM>. In addition, in the case in which the pouch-shaped case <NUM> is constituted by two laminate sheets and thus all surfaces of the pouch-shaped case are attached to each other by sealing without being folded, the gas pocket <NUM> shown in <FIG> may be provided at at least one sealed surface of the pouch-shaped case.

<FIG> is a cross-sectional view showing a pouch-shaped secondary battery having a hidden-type gas pocket according to a third embodiment of the present invention. Unlike the previously described first and second embodiments of the present invention, in each of which the gas pocket <NUM> starts to be formed from the middle portion of the side surface of the battery, this embodiment is configured to have a structure in which a gas pocket <NUM> starts to be formed at the corner at which the side surface of the pouch-shaped case <NUM> meets another surface (the upper surface or the lower surface) of the pouch-shaped case and is then folded so as to cover the side surface of the battery.

The gas pocket <NUM> (31a and 32a) may be formed at one of the opposite side surfaces of the battery.

The other components of this embodiment may be configured so as to be identical or similar to the components of the embodiments that were previously described, and therefore a duplicate description thereof will be omitted.

<FIG> is a cross-sectional view showing a pouch-shaped secondary battery having a hidden-type gas pocket according to a fourth embodiment of the present invention. This embodiment is similar in construction to the third embodiment, except that, in the case in which sealed surfaces <NUM> are formed at both opposite sides of the battery, a gas pocket 32a is provided at each of the sealed surfaces <NUM>.

In addition, the opposite gas pockets 32a start to be formed from opposite sides in the diagonal direction.

<FIG> is a cross-sectional view showing a pouch-shaped secondary battery having a hidden-type gas pocket according to a fifth embodiment of the present invention. Unlike the embodiments previously described, a gas pocket <NUM> is formed as the result of being bent toward the upper surface or the lower surface of the battery, rather than toward the side surface of the battery.

At this time, the gas pocket <NUM> (<NUM> and <NUM>) may be formed at only one of the opposite sides of the battery.

<FIG> is a cross-sectional view showing a pouch-shaped secondary battery having a hidden-type gas pocket according to a sixth embodiment of the present invention. This embodiment shows the construction in which a gas pocket <NUM> is formed at the side surface of the battery so as to have a bellows structure.

Even at this time, a gas pocket <NUM> having the same structure may be formed at the sealed surface of the battery, or the gas pocket <NUM> may be formed at opposite sides of the battery.

In addition, since the gas pocket <NUM> is formed so as to have a bellows structure, bellows parts constituting the bellows structure may be attached to each other via an adhesive member such that the gas pocket <NUM> is stably fixed in tight contact with the side surface of the battery before gas is generated.

Meanwhile, a battery module may be configured to include one or more pouch-shaped secondary batteries described above. The battery module is configured to include at least one pouch-shaped secondary battery cell. A plurality of pouch-shaped secondary battery cells may be combined in order to constitute the battery module. In addition, a plurality of battery modules may be combined in order to manufacture a battery pack.

Claim 1:
A pouch-shaped secondary battery comprising:
an electrode assembly (<NUM>); and
a pouch-shaped case (<NUM>) configured to receive the electrode assembly (<NUM>), wherein
the pouch-shaped case (<NUM>) has therein a gas pocket (<NUM>) configured such that at least a portion of the gas pocket is maintained in a folded state and such that, when gas is generated in the pouch-shaped case, the gas pocket is unfolded to form a space configured to collect the gas,
the pouch-shaped case is configured to have a quadrangular planar structure in which a perimetric surface of this quadrangular plane comprises a single surface (<NUM>) that is folded and three surfaces (<NUM>, <NUM>) that are attached by sealing, the gas pocket is formed at the single surface (<NUM>) that is folded,
the pouch-shaped case (<NUM>) comprises a case main body (<NUM>), in which the electrode assembly is mounted, and the gas pocket (<NUM>) formed at one side of the case main body (<NUM>), and
the gas pocket (<NUM>) is configured to have a structure in which the gas pocket (<NUM>) is bent from the case main body (<NUM>) and is then in tight contact with the case main body (<NUM>) .