Patent Description:
The present invention relates to a secondary battery in which an electrode assembly and an electrolyte are embedded in a pouch, and more particularly, to a pouch-type secondary battery having a valve capable of discharging a gas to the outside when the gas is generated in the pouch.

The demands for high-efficiency secondary batteries are rapidly increasing in the mobile device and electric vehicle fields. Among such the secondary batteries, a lithium secondary battery having high energy density, maintaining a relatively high voltage, and having a low self-discharge rate is commercially widely used, and research and development for improving performance thereof is actively being conducted.

The secondary battery has a structure in which an electrode assembly and an electrolyte are embedded in a case such as a can or a pouch. The electrode assembly has a structure in which positive electrodes, separators, and negative electrodes are repeatedly stacked. In general, the electrode assembly may be classified into a winding type electrode assembly in which the positive electrodes, the separators, and the negative electrodes, which are in the stacked state, are rolled to be embedded in the case and a stack type (stacked) electrode assembly in which the positive electrodes, the separators, and the negative electrodes, each of which is cut to a predetermined size, are stacked.

Since the winding type electrode assembly has a spirally wound structure, the winding type electrode assembly is suitable for being mounted on a cylindrical battery, but is disadvantageous in space utilization for a prismatic or pouch type battery. On the other hand, since the stack type electrode assembly is adjusted in size when the electrode and the separator are cut, the prismatic shape fitted with the case is easily obtained, but a manufacturing process is relatively complicated, and the stack type electrode assembly is relatively vulnerable to an external impact. Also, a stack & folding method has been developed to combine the advantages of the winding type and the stack type. In the stack & folding method, a C-type bicell (a bicell having a stack structure of a positive electrode/separator/negative electrode/separator/positive electrode) and an A-type bicell (a bicell having a stack structure of a negative electrode/separator/positive electrode/separator/negative electrode) are placed on a folding separator to fold the bicells, thereby manufacturing the electrode assembly.

The electrode assembly manufactured in various manners as described above is mounted in a case such as a can or a pouch.

Among them, the pouch-type battery has advantages such as higher energy density per unit weight and volume, enables thinner and lighter battery, as well as a lower material cost as an exterior, and thus has been actively developed in recent years. As illustrated in <FIG>, which illustrates a state in which an electrode assembly <NUM> is mounted in a state in which a pouch <NUM> is opened, the pouch-type secondary battery is manufactured so that the electrode assembly <NUM> is seated in the pouch <NUM> in a state in which upper and lower portions of the pouch <NUM> are separated from each other, and when an electrolyte is injected, sealing portions 2a and 2b formed on edges of the upper and lower portions are sealed. Here, an end of an electrode lead 3a drawn out from the electrode assembly <NUM> is sealed in a state of being disposed to protrude to the outside.

The pouch-type battery has a problem in that swelling occurs during the charging/discharging in the manufacturing process and during the use as a charging/discharging device after the manufacturing is performed.

Such swelling is a phenomenon in which a gas is generated inside the pouch <NUM> due to the vaporization of the electrolyte to deform an outer appearance of the pouch <NUM> and deteriorate charge/discharge performance of the secondary battery, and in severe cases, there is a risk of explosion.

Therefore, when the gas is generated inside the pouch, it is necessary to remove the gas.

Document <CIT> discloses a battery packaging according to the preamble of claim <NUM>, which permits gas generated inside of the battery package to safely escape through a vent.

In order to solve the above-described problem, an object of the present invention is to provide a secondary battery having a valve capable of discharging a gas to the outside when the gas is generated inside a pouch to increase in internal pressure.

The present invention for achieving the above-described object provides a secondary battery as defined in the annexed claims.

The present invention may additionally provide a secondary battery module.

In the present invention having the above configuration, the adhesive may be filled in the inner tube to prevent the electrolyte from leaking and prevent the external moisture from being permeated, but only when the pressure inside the pouch increases, the gap may be generated to discharge the gas, thereby efficiently preventing the swelling from occurring.

Since the inner tube is disposed in the outer tube so that the inner tube is deformed to be expanded in diameter, the inner tube may be protected from the external impact.

Gaseous nitrogen may be injected into the chamber formed between the inner tube and the outer tube to protect the inner tube, and the gaseous nitrogen may be contracted while the inner tube is expanded to facilitate the generation of the gap in the adhesive.

Furthermore, the plurality of hooks may be installed on each of one surface and the other surface, which face each other, within the inner tube so that the hooks are physically coupled to each other in the hook-and-loop fastener manner to adjust the internal pressure standard within the pouch, in which the gap is generated in the adhesive, and the expansion speed of the gap.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

The present invention relates to a secondary battery provided with a pouch <NUM> in which sealing portions 2a and 2b formed on an edge <NUM> are sealed when an electrode assembly <NUM> and an electrolyte are enclosed, and more particularly, to a secondary battery provided with a valve <NUM> so that when a gas is generated inside the pouch <NUM> to increase in internal pressure, the gas is discharged to the outside. Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings.

<FIG> is a view illustrating a state in which a valve according to a first embodiment of the present invention is mounted in a pouch-type secondary battery, <FIG> is a transverse cross-sectional view of the valve according to the first embodiment of the present invention, and <FIG> is a transverse cross-sectional view illustrating a state a gap g is generated in an adhesive in the valve according to the first embodiment of the present invention.

Referring to the drawings, as illustrated in <FIG>, a secondary battery according to this specification comprises a valve <NUM>. The valve <NUM> is mounted so that one end of the valve <NUM> is disposed inside a pouch, and the other end of the valve <NUM> disposed outside the pouch (in more detail, the valve <NUM> is mounted between sealing portions adhering to each other). That is, the valve <NUM> is disposed in parallel to an electrode lead 3a that is drawn out from the electrode assembly to protrude out of the pouch at an interval.

The valve <NUM> has a function of discharging a gas generated inside the pouch <NUM> to the outside and has a structure in which a passage is blocked by an adhesive <NUM> in a tube <NUM> in which the passage is formed to communicate between the inside and the outside.

That is, as illustrated in <FIG>, the valve <NUM> comprises an inner tube <NUM> which has one end disposed inside the pouch <NUM> and the other end disposed outside the pouch <NUM>, and is filled with the adhesive <NUM> and an outer tube <NUM> mounted on a sealing portion so that one end thereof is disposed inside the pouch <NUM>, and the other end thereof is disposed outside the pouch <NUM>, and also mounted so that the inner tube <NUM> is inserted in a longitudinal direction inside the outer tube <NUM>.

The inner tube <NUM> is made of a material that is capable of being deformed when swelling is generated in the pouch to increase in pressure. Thus, when the internal pressure increases, a gap g is generated in a portion that is filled with the adhesive <NUM>, and when the gap g opens the adhesive <NUM> in the longitudinal direction of the inner tube <NUM>, the gas within the pouch is discharged to the outside through the gap g.

Here, both ends of the outer tube <NUM> and the inner tube <NUM> are connected to each other to be sealed so that a chamber C that is a sealed space is formed between the outer tube <NUM> and the inner tube <NUM>. The inner tube <NUM> may be deformed within the outer tube <NUM> in a direction in which a diameter thereof is expanded.

The outer tube <NUM> is made of a material that is not deformed even when the swelling occurs. Thus, when the swelling occurs to increase in pressure within the pouch <NUM>, the inner tube <NUM> is deformed so that a volume of the chamber C is contracted.

That is, when a pressure of the gas acts on the end of the inner tube <NUM> inside the pouch <NUM>, stress acts on a surface of the adhesive <NUM>, and thus, at least one or more gaps g are generated as illustrated in <FIG> (one gap may be generated in an edge portion or a center, unlike the shape of <FIG>). That is, although a plurality of gaps g are formed in <FIG>, and a passage through which the gas passes is illustrated by a single arrow in <FIG>, the plurality of gaps g or one gap g may be formed in plurality according to a kind or type of the adhesive, and also, the gap may have various sizes.

As illustrated in <FIG>, which illustrates a longitudinal cross-sectional view and a transverse cross-sectional view (upper and lower drawings at the left) when the valve <NUM> is in a normal state and a longitudinal cross-sectional view and a transverse cross-sectional view (upper and lower drawings at the right) when the gas is generated inside the pouch to increase in an internal pressure, since a pressure is continuously applied to the gap g, the gap g is expanded in the longitudinal direction of the inner valve <NUM> and opened up to the outside of the inner valve <NUM>.

Thus, the gas inside the pouch <NUM> is discharged to the outside along the passage opened by the gap g. Simultaneously with the formation of the gap g and the expansion of the gap, the inner tube <NUM> increases in diameter so that the chamber C is contracted.

Here, since no deformation occurs in shape of the outer valve <NUM>, contraction of the gas in the chamber C and expansion of the inner valve <NUM> may be performed at the same time. Since the contraction of the air inside the chamber C and the increase in diameter of the inner tube <NUM> are performed at the same time, the gap g that allows a free volume of the adhesive <NUM> to increase may increase in size to form the passage through which the gas is discharged.

It is preferable that each of the outer tube <NUM> and the inner tube <NUM> is made of polypropylene, which is a material contained in the pouch so that the pouch <NUM> is sealed when sealing.

However, the outer tube <NUM> is manufactured with relatively low flexibility and high rigidity compared to the inner tube <NUM>, and the inner tube <NUM> is manufactured with relatively high flexibility and low rigidity compared to the outer tube <NUM>. Such, the flexibility and rigidity may be adjusted by controlling molding conditions or adding additives.

Furthermore, gaseous nitrogen (N<NUM>) may be injected into the chamber C, or other stable gases may be injected instead of the gaseous nitrogen.

It is preferable that each of the outer tube <NUM> and the inner tube <NUM> has a circular or elliptical cross-section so that a relatively uniform pressure is applied in all directions, but may be manufactured to have a square or other polygonal cross-section. Also, each of the outer tube <NUM> and the inner tube <NUM> may be manufactured so that a portion inside the pouch <NUM> has a relatively large diameter, and an opposite portion has a relatively small diameter so as to efficiently apply the pressure of the gas.

Furthermore, the adhesive <NUM> may be a material containing an epoxy binder or a material containing an acrylic binder. The adhesive <NUM> may be selected from a variety of materials that do not react with the electrolyte and may be filled in the inner tube <NUM> as gel or in the form of a gel as well as a soft solid state.

Also, in the present invention, the gap g formed in the inner tube <NUM> may be filled again after the gas is discharged. Thus, the valve <NUM> according to the present invention may repeatedly provide a function of sealing after repeatedly discharging the gas until the lifespan of the secondary battery is over.

<FIG> is a transverse cross-sectional view of a valve according to a second embodiment of the present invention. A valve <NUM> according to this embodiment has a structure in which an inner tube <NUM> is disposed inside an outer tube <NUM>, and an adhesive <NUM> is filled in the inner tube <NUM>, like that in the first embodiment. Also, in order to increase in physical bonding force, a plurality of hooks <NUM> are additionally installed as illustrated in <FIG>.

That is, an inner circumferential surface of the inner tube <NUM> is provided with a plurality of hooks <NUM> paired to increase in bonding force in a specific direction.

Since the hooks <NUM> are physically coupled to each other in a hook-and-loop fastener method (i.e., a Velcro tape coupling method), a pressure at which a gap g is generated and an expansion speed of the gap may be reduced.

In the present invention having the above configuration, the adhesive <NUM> may be filled in the inner tube <NUM> to prevent the electrolyte from leaking and prevent the external moisture from being permeated, but only when the pressure inside the pouch increases, the gap g may be generated to discharge the gas, thereby efficiently preventing the swelling from occurring.

Since the inner tube <NUM> is disposed in the outer tube <NUM> so that the inner tube <NUM> is deformed to be expanded in diameter, the inner tube <NUM> may be protected by the outer tube <NUM> from the external impact.

Gaseous nitrogen may be injected into a chamber C formed between the inner tube <NUM> and the outer tube <NUM> to protect (buffer) the inner tube <NUM>, and the gaseous nitrogen may be contracted while the inner tube <NUM> is expanded to facilitate the generation of the gap in the adhesive.

Furthermore, the plurality of hooks <NUM> may be installed on each of one surface and the other surface, which face each other, within the inner tube <NUM> so that the hooks are physically coupled to each other in the hook-and-loop fastener manner to adjust the internal pressure standard within the pouch, in which the gap g is generated in the adhesive <NUM>, and the expansion speed of the gap.

Claim 1:
A secondary battery provided with a pouch (<NUM>), in which a sealing portion (2a, 2b) formed on an edge (<NUM>) thereof is sealed when an electrode assembly (<NUM>) and an electrolyte are enclosed, the secondary battery comprising:
a valve (<NUM>) which is mounted on a sealing portion (2a, 2b) so that one end thereof is disposed inside the pouch (<NUM>), and the other end thereof is disposed outside the pouch and discharges a gas generated inside the pouch to the outside,
characterised in that
the valve (<NUM>) comprises an inner tube (<NUM>) filled with an adhesive (<NUM>) and made of a material that is deformed when swelling occurs, and
when the swelling occurs due to increase in pressure inside the pouch (<NUM>), a gap is generated in a portion that is filled with the adhesive (<NUM>), and the gas within the pouch (<NUM>) is discharged to the outside though the gap.