Patent Description:
The present invention relates to a pouch-shaped battery cell including a sealed portion venting adjustment means. More particularly, the present invention relates to a pouch-shaped battery cell including a venting adjustment means provided at a sealed portion of the pouch-shaped battery cell so as to adjust discharge of gas depending on the pressure in the pouch-shaped battery cell.

There are a lithium ion battery, a lithium polymer battery, a nickel-cadmium battery, a nickel-hydride battery, and a nickel-zinc battery as secondary batteries. The operating voltage of a unit cell of the secondary battery is about <NUM>. 0V to <NUM>. When output voltage higher than the above operating voltage is required, therefore, a plurality of unit cells may be connected to each other in series to constitute a cell assembly. In consideration of output voltage and capacity, cell assemblies may be connected to each other in series and/or in parallel to constitute a battery module, and a battery pack may be manufactured using a plurality of battery modules.

The secondary batteries may be classified into a cylindrical battery, a prismatic battery, and a pouch-shaped battery based on the shape of a battery case. Among these batteries, the pouch-shaped battery, which can be stacked with high integration, has high energy density per unit weight, is inexpensive, and can be easily deformed, has attracted considerable attention. A pouch-shaped battery cell, which means a battery cell configured such that a battery case is made of a laminate sheet, has a structure in which an electrode assembly is mounted in the battery case.

The pouch-shaped battery cell has a danger in that gas is generated in the battery cell during use thereof, such as charging and discharging, whereby the pouch-shaped battery case may swell and explode.

In order to prevent such a danger, as shown in <FIG>, Patent Document <NUM> discloses a battery cell configured such that a main gas discharge pipe <NUM> and an auxiliary gas discharge pipe <NUM> are provided at a sealed portion <NUM> of a battery case <NUM> in order to rapidly discharge gas generated in the battery cell to the outside.

The battery cell of Patent Document <NUM> is manufactured through a step of performing sealing in the state in which the main gas discharge pipe <NUM> is located at the sealed portion, a part of the sealed portion <NUM> is incised to expose a part of the main gas discharge pipe <NUM> and gas is discharged to the outside through the exposed part of the main gas discharge pipe at the time of gas discharge, and the exposed part of the main gas discharge pipe <NUM> is hermetically sealed by thermal fusion when gas discharge is completed. As a result, the process is complicated, and productivity is lowered.

<CIT> ("Patent Document <NUM>")
<CIT> discloses a secondary battery. <CIT> discloses a film package energy storage device.

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 cell capable of adjusting venting through a venting adjustment means mounted to a sealed portion of the pouch-shaped battery cell, from which an electrode lead protrudes, depending on the pressure of gas generated in the battery cell.

In order to accomplish the above object, the present invention provides a pouch-shaped battery cell as laid out in appended claim <NUM>.

In addition, the present invention provides a pouch-shaped battery cell manufacturing method as laid out in appended claim <NUM>.

In addition, the present invention provides a battery pack including the pouch-shaped battery cell.

In addition, the present invention may provide various combinations of the above solving means.

A pouch-shaped battery cell according to the present invention has an advantage in that a venting adjustment means is mounted to a sealed portion, whereby it is possible to automatically induce venting when the pressure in the pouch-shaped battery cell increases as the result of gas being generated in the pouch-shaped battery cell, and therefore it is possible to prevent explosion of the battery cell due to swelling thereof.

In addition, the pouch-shaped battery cell according to the present invention has an advantage in that, when the pressure in the pouch-shaped battery cell decreases after venting is performed by the venting adjustment means, the sealed portion is closed again, whereby it is possible to use the battery cell even after venting.

In addition, the pouch-shaped battery cell according to the present invention has an advantage in that a complicated process of forming a separate means for venting is not necessary at the time of manufacture of the pouch-shaped battery cell, whereby the manufacturing process is simplified.

In addition, all numeric ranges include the lowest value, the highest value, and all intermediate values therebetween unless the context clearly indicates otherwise.

A pouch-shaped battery cell according to the present invention will be described with reference to the accompanying drawings.

<FIG> is a plan view showing a pouch-shaped battery cell including a venting adjustment means according to an embodiment of the present invention.

When describing the pouch-shaped battery cell <NUM> according to the present invention with reference to <FIG>, the pouch-shaped battery cell <NUM> includes an electrode assembly <NUM>, a battery case <NUM> configured to receive the electrode assembly <NUM>, an electrode lead <NUM> joined to the electrode assembly <NUM>, a part of the electrode lead protruding outwards from the battery case <NUM>, and a venting adjustment means <NUM>.

First, the electrode assembly <NUM> may be a jellyroll type assembly, which is configured to have a structure in which a long sheet type positive electrode and a long sheet type negative electrode are wound in the state in which a separator is interposed therebetween, a stacked type assembly which is configured to have a structure in which a rectangular positive electrode and a rectangular negative electrode are stacked in the state in which a separator is interposed therebetween, a stacked and folded type assembly, which is configured to have a structure in which unit cells are wound using a long separation film, or a laminated and stacked type assembly, which is configured to have a structure in which battery cells are stacked and attached to each other in the state in which a separator is interposed therebetween. However, the present invention is not limited thereto.

The electrode assembly <NUM> is received in the pouch-shaped battery case <NUM>.

The pouch-shaped battery case <NUM> is generally configured to have a laminate sheet structure including an inner layer, a metal layer, and an outer layer. The inner layer is disposed in direct contact with the electrode assembly, and therefore the inner layer must exhibit high insulation properties and high resistance to an electrolytic solution. In addition, the inner layer must exhibit high sealability in order to hermetically seal the battery case from the outside, i.e. a thermally-bonded sealed portion between inner layers must exhibit excellent thermal bonding strength.

The inner layer may be made of a material selected from among a polyolefin-based resin, such as polypropylene, polyethylene, polyethylene acrylate, or polybutylene, a polyurethane resin, and a polyimide resin, which exhibit excellent chemical resistance and high sealability. However, the present invention is not limited thereto, and polypropylene, which exhibits excellent mechanical-physical properties, such as tensile strength, rigidity, surface hardness, and impact resistance, and excellent chemical resistance, is most preferably used.

The metal layer, which is disposed so as to abut the inner layer, corresponds to a barrier layer configured to prevent moisture or various kinds of gas from permeating into the battery from the outside. An aluminum thin film, which is lightweight and easily shapeable, may be used as a preferred material for the metal layer.

The outer layer is provided on the other surface of the metal layer. The outer layer may be made of a heatresistant polymer that exhibits excellent tensile strength, resistance to moisture permeation, and resistance to air transmission such that the outer layer exhibits high heat resistance and chemical resistance while protecting the electrode assembly. As an example, the outer layer may be made of nylon or polyethylene terephthalate. However, the present invention is not limited thereto.

A sealed portion <NUM> configured to hermetically seal the battery case <NUM> after the electrode assembly <NUM> is received in the battery case is formed at an outer periphery of the battery case <NUM>.

In addition, the pouch-shaped battery cell <NUM> generally includes an electrode lead <NUM> constituted by a pair of a positive electrode lead and a negative electrode lead.

The electrode lead <NUM> is joined to tabs of the electrode assembly <NUM> by welding, and a part of the electrode lead protrudes outwards from the battery case <NUM> so as to be electrically connected to another battery cell or devices when the electrode assembly is received in the battery case <NUM>.

Meanwhile, the positive electrode lead and the negative electrode lead may protrude in various directions. In general, however, the positive electrode lead and the negative electrode lead may protrude in opposite directions, or the positive electrode lead and the negative electrode lead may protrude in the same direction. In <FIG>, as a non-limiting example, the positive electrode lead and the negative electrode lead are shown as protruding in opposite directions or different directions.

In addition, a lead film may be used in order to improve sealing between the electrode lead <NUM> and the battery case <NUM>; however, the present invention is not limited thereto.

<FIG> is a perspective view of the venting adjustment means according to the embodiment of the present invention.

When describing the venting adjustment means <NUM> according to the present invention with reference to <FIG>, the venting adjustment means <NUM> is mounted to the sealed portion <NUM> of the battery case <NUM>, particularly the part of the sealed portion <NUM> from which the electrode lead <NUM> protrudes.

The venting adjustment means <NUM> includes a main body portion <NUM>, an elastic portion <NUM>, and an electrode lead insertion hole <NUM>.

First, the main body portion <NUM>, which is a portion that forms an external framework of the venting adjustment means <NUM>, includes a material having a predetermined level of strength such that the main body portion is not deformed even though the sealed portion <NUM>, to which the venting adjustment means <NUM> is mounted, is opened as the pressure in the battery cell <NUM> increases. It is preferable for the main body portion to be made of a metal material in consideration of strength and shapeability; however, the present invention is not limited thereto, and various kinds of materials may be used.

Next, the elastic portion <NUM>, which is a portion that is located inside the main body portion <NUM> so as to contact the battery case <NUM>, includes a material that is elastic so as to be deformed such that the sealed portion <NUM>, at which the venting adjustment means <NUM> is mounted, can be opened when the pressure in the battery cell <NUM> increases to a predetermined value or more.

Any of various known rubber and polymer materials may be used as the elastic material.

The electrode lead insertion hole <NUM> is a throughhole configured to allow the electrode lead <NUM> to be inserted therethrough when the venting adjustment means <NUM> is mounted to the battery cell <NUM>.

In <FIG>, the venting adjustment means <NUM> is shown as being disposed over one of four side surfaces of the battery cell <NUM> in each direction in which the electrode lead <NUM> protrudes; however, the present invention is not limited thereto. The venting adjustment means according to the present invention may be applied to any position of the sealed portion of the pouch-shaped battery case. In addition, the venting adjustment means may be disposed only at a part of the sealed portion, not the entirety of the sealed portion, and the venting adjustment means may be configured without the electrode lead insertion hole.

<FIG> is a sectional view taken along line B-B' of <FIG>, and <FIG> is a sectional view schematically showing the shape of the pouch-shaped battery cell of <FIG> when venting occurs.

When describing the principle by which the venting adjustment means <NUM> is operated with reference to <FIG>, when the pressure in the battery cell <NUM> is a predetermined value or less, the sealed portion <NUM> remains closed, as shown in <FIG>, and when the pressure in the battery cell <NUM> is the predetermined value or more, the sealed portion <NUM> is opened such that gas in the battery cell is discharged to the outside, as shown in <FIG>.

When the gas is somewhat discharged and the pressure in the battery cell is lowered to the predetermined value or less, the sealed portion <NUM> is closed again.

That is, venting is adjusted based on the principle that, when the pressure in the battery cell is greater than the restoring force of the elastic portion <NUM>, the sealed portion <NUM> is opened and venting occurs, and when the pressure in the battery cell is less than the restoring force of the elastic portion <NUM>, the sealed portion <NUM> is closed.

Consequently, the pressure at which venting occurs may be appropriately adjusted depending on the kind and thickness of the material of which the elastic portion <NUM> is made.

Meanwhile, in <FIG>, an end 121a of the sealed portion and an inner surface 142a of the elastic portion are shown as being spaced apart from each other by a predetermined distance. Unlike <FIG>, however, the end 121a of the sealed portion and the inner surface 142a of the elastic portion may abut each other.

The reason for this is that, even in this case, gas can be discharged through a side surface of the venting adjustment means <NUM>.

<FIG> is a sectional view of a pouch-shaped battery cell including a venting adjustment means according to another embodiment of the present invention.

The venting adjustment means <NUM> of <FIG> also includes a main body portion <NUM>, an elastic portion <NUM>, and an electrode lead insertion hole (not shown), and is different from the venting adjustment means <NUM> described above in that the elastic portion <NUM> is formed over the entirety of the surface of the venting adjustment means that abuts the battery case <NUM>.

Since the elastic portion <NUM> is formed, as described above, there is an advantage in that it is possible to prevent a possibility of the battery case <NUM> being damaged by the main body portion <NUM> when or after the venting adjustment means <NUM> is mounted.

Meanwhile, a method of manufacturing a pouch-shaped battery cell <NUM> including a venting adjustment means <NUM> or <NUM> according to the present invention includes <NUM>) a step of manufacturing an electrode assembly <NUM> using electrodes and a separator, <NUM>) a step of joining an electrode lead <NUM> to the electrode assembly <NUM>, <NUM>) a step of receiving the electrode assembly <NUM> having the electrode lead <NUM> joined thereto in a pouch-shaped battery case <NUM>, <NUM>) a step of hermetically sealing the remaining outer peripheries of the battery case <NUM> excluding an outer periphery through which an electrolytic solution is injected, and <NUM>) a step of mounting a venting adjustment means <NUM> or <NUM> to one of sealed portions <NUM> of the battery case <NUM> in a direction in which the electrode lead <NUM> protrudes.

The pouch-shaped battery cell manufacturing method further includes a step of injecting an electrolytic solution and a step of hermetically sealing an electrolytic solution injection portion after the step of mounting the venting adjustment means <NUM> or <NUM>.

Here, a thermal fusion method is generally used as a method of hermetically sealing the outer peripheries of the battery case. In the step of hermetically sealing the remaining outer peripheries of the battery case excluding the outer periphery through which the electrolytic solution is injected, the outer peripheries of the battery case may be hermetically sealed at the same fusion strength; however, it is preferable for the sealed portion <NUM> in the direction in which the electrode lead <NUM> protrudes to be more weakly fused than the sealed portions <NUM> in other different directions in order to guide gas to be discharged in a direction in which the venting adjustment means <NUM> or <NUM> is mounted.

That is, it is preferable for the fusion strength of the sealed portion <NUM> to which the venting adjustment means <NUM> or <NUM> is mounted to be set within a range within which the sealed portion can be split off at pressure lower than the inner pressure at which the venting adjustment means <NUM> or <NUM> is opened.

Of course, all of the sealed portions <NUM> may be hermetically sealed at the same fusion strength, and then joining strength of the remaining sealed portions <NUM> excluding the sealed portion <NUM> to which the venting adjustment means <NUM> or <NUM> is mounted may be increased using an additional method such that the joining strength of the sealed portion <NUM> to which the venting adjustment means <NUM> or <NUM> is mounted is relatively weak.

Claim 1:
A pouch-shaped battery cell (<NUM>) comprising:
an electrode assembly (<NUM>, <NUM>);
a pouch-shaped battery case (<NUM>, <NUM>) configured to receive the electrode assembly (<NUM>, <NUM>); and
an electrode lead (<NUM>, <NUM>) extending from the electrode assembly (<NUM>, <NUM>), a part of the electrode lead (<NUM>, <NUM>) protruding outwards from the pouch-shaped battery case (<NUM>, <NUM>), wherein
a sealed portion (<NUM>, <NUM>) is formed at an outer periphery of the pouch-shaped battery case (<NUM>, <NUM>),
a venting adjustment means (<NUM>, <NUM>) is mounted to a part of the sealed portion (<NUM>, <NUM>) in a direction in which the electrode lead (<NUM>, <NUM>) protrudes, and
the venting adjustment means (<NUM>, <NUM>) is configured to adjust opening and closing of the sealed portion (<NUM>, <NUM>) having the venting adjustment means (<NUM>, <NUM>) mounted thereto based on a pressure of a gas in the pouch-shaped battery case (<NUM>, <NUM>);
characterized in that the venting adjustment means (<NUM>, <NUM>) comprises an external main body portion (<NUM>, <NUM>) and an inner elastic portion (<NUM>, <NUM>), the inner elastic portion (<NUM>, <NUM>) directly abutting the pouch-shaped battery case (<NUM>, <NUM>).