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 <NUM>, it is necessary to remove the gas to the outside.

<CIT>, <CIT>, <CIT>, <CIT> and <CIT> each aim to discharge gas from inside a pouch to the outside, thereby preventing the pouch from exploding.

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 is defined in the set of claims and provides a secondary battery in which an electrode assembly and an electrolyte are inserted and injected into a pouch, and an edge of the pouch is sealed to form a sealing portion, the secondary battery comprising: a valve fixed to the sealing portion so that one end thereof faces the inside of the pouch, and the other end thereof faces the outside of the pouch, wherein the valve comprises: a body forming a passage having opened one end facing the inside of the pouch and provided with a chamber connected to the passage, wherein a discharge hole communicating with the outside is formed in the chamber; a gate seated on a hook protrusion forming a boundary between the passage and the chamber to open or close the passage; and a spring mounted to apply elastic force in a direction in which the gate is closed, wherein when a gas is generated inside the pouch, a pressure of the gas overcomes the elastic force of the spring, the gate is opened to discharge the gas through the discharge hole.

An O-ring may be mounted at a point of the hook protrusion, at which the gate is seated, so that sealing is achieved when the gate is closed.

A blocking film for preventing the electrolyte from being permeated may be mounted on the body at an inlet-side of the passage, and the blocking film may be torn or separated from a mounted position when a gas is generated inside the pouch to increase in internal pressure.

The blocking film may be made of a material that does not cause a chemical reaction with the electrolyte. The blocking film may be manufactured as a thin film made of polypropylene or polytetrafluoroethylene.

The blocking film may adhere to the body by using a pressure sensitive adhesive.

An auxiliary discharge hole is formed so that when the gate slides inside the chamber, air within the chamber is discharged, wherein the auxiliary discharge hole is formed at an opposite side of the discharge hole with the gate therebetween.

The gate may comprise a body seated on the hook protrusion and a pillar expanded form the body to protrude to be inserted into the passage, wherein a gasket having a ring shape may be fitted to an outer circumferential surface of the pillar to seal a gap between the outer circumferential surface of the pillar and an inner circumferential surface of the passage.

An inclined surface may be formed along a circumference of the pillar so that the gas is gradually introduced into the chamber while the pillar slides.

The valve may be disposed in parallel to an electrode lead that is drawn out from the electrode assembly to protrude out of the pouch.

The present invention may additionally provide a secondary battery module manufactured by coupling the plurality of secondary batteries having the above-described configuration to each other.

In the present invention having the configuration as described above, when the gas is generated inside the pouch, and the pressure of the gas overcomes the elastic force of the spring, the gate may be opened to discharge to the discharge hole, thereby efficiently preventing the swelling from occurring and preventing the moisture and the foreign substances from being introduced from the outside of the valve.

The O-ring may be mounted at the point of the hook protrusion, at which the gate is seated, to prevent the electrolyte from leaking.

Furthermore, the blocking film may be mounted on the inlet-side of the passage to fundamentally block the introduction of the electrolyte into the valve when the pressure inside the pouch is in the normal range.

The blocking film may be made of the material that does not cause the chemical reaction with the electrolyte to prevent the electrolyte from being deteriorated in performance.

In the valve according to the present invention, the auxiliary discharge hole may be formed in the opposite side of the discharge hole to prevent the air resistance from adversely affecting the sliding of the valve.

In addition, the gasket may be fitted into the gate to prevent the gas from leaking, and the inclined surface may be formed on the pillar so that the gas is gradually discharged.

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 in which an electrode assembly and an electrolyte are inserted into a pouch, and an edge of the pouch is sealed to form a sealing portion. Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

<FIG> is a view illustrating a state in which a valve is mounted in a secondary battery according to a first embodiment of the present invention, <FIG> is a cross-sectional view (left) illustrating a state in which a gate is closed before a gas is generated in a pouch and a cross-sectional view (right) illustrating a state in which the gas is generated to open the gate by a pressure of the gas in the valve according to the first embodiment of the present invention, and <FIG> is a view illustrating more clearly a mounted state of a gasket in <FIG>.

Referring to the drawings, a secondary battery according to this embodiment comprises a valve <NUM>, and the valve <NUM> is fixedly mounted so that one end thereof faces the inside of a pouch <NUM>, and the other end thereof faces the outside of the pouch <NUM>. Here, 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 <NUM> at an interval.

The valve <NUM> has a structure in which a gate <NUM> is fixed to the sealing portion and mounted inside a body <NUM>, in which a passage is formed, so that a gas is accessible.

That is, as illustrated in <FIG> in more detail, the body <NUM> has the passage having one end opened and facing the inside of the pouch <NUM> and the other end extending from the one end to the other side in a longitudinal direction, and the passage <NUM> is opened to a chamber <NUM>.

The chamber <NUM> has a structure in which an end opposite to the end of the passage <NUM> is blocked, and a discharge hole <NUM> is formed so as to communicate with the outside in a portion of a sidewall. The valve <NUM> is fixed to the sealing portion in a state in which the discharge hole <NUM> is exposed to the outside. The body <NUM> is made of a metal, ceramic, a synthetic resin, or the like having excellent chemical resistance.

Also, the gate <NUM> is seated on a hook protrusion forming a boundary between the passage <NUM> and the chamber <NUM> to open or close the passage <NUM>. The hook protrusion is a boundary point formed by a difference between an inner diameter of the passage <NUM> and an inner diameter of the chamber <NUM>, and the gate <NUM> is mounted to shield the hook protrusion in the chamber <NUM>.

The gate <NUM> is connected to a spring <NUM> so that elastic force acts in a direction in which the gate <NUM> is closed. The spring <NUM> is a compression spring that resists compression force and has one end fixed to a wall surface (disposed at an opposite side of the passage) of the chamber <NUM> and the other end fixed to the gate <NUM>.

Thus, the gate <NUM> is opened only when force that overcomes the elastic force of the spring <NUM> is applied.

Also, an O-ring <NUM> is mounted at a point of the hook protrusion, at which the gate <NUM> is seated, so that sealing is achieved when the gate <NUM> is closed. When the gate <NUM> is closed, the O-ring <NUM> is pressed by the elastic force of the spring <NUM> and thus is elastically deformed to seal a gap that may occur between the gate <NUM> and the body <NUM>.

Furthermore, an auxiliary discharge hole <NUM> is additionally formed so that air in the chamber <NUM> is discharged when the gate <NUM> slides inside the chamber <NUM>. Since the auxiliary discharge hole <NUM> is formed at an opposite side of the discharge hole <NUM> with the gate <NUM> therebetween, when a space in which the spring <NUM> is disposed is contracted, the air may be discharged to the outside before being compressed prevent the sliding of the gate <NUM> from being disturbed by air resistance.

The gate <NUM> according to this embodiment comprises a disk-shaped body <NUM> that is seated on the hook protrusion and a cylindrical pillar <NUM> that is expanded from the body <NUM> to protrude to be inserted into the passage <NUM>.

The body <NUM> shields a gap between the passage <NUM> and the chamber <NUM> when the gate <NUM> is in a closed state, and the pillar <NUM> extends from the body <NUM> so as to be inserted into the passage <NUM>, thereby guiding the sliding of the body <NUM>.

Furthermore, the pillar <NUM> has an inclined surface 22a along a circumference of the pillar <NUM> so that the gas is gradually introduced into the chamber <NUM> while the pillar <NUM> slides, and a contact area increases when the gas is introduced into the passage <NUM> to concentrate a pressure. The inclined surface 22a may be formed as a plane inclined at a predetermined angle or may be formed in a convexly rounded curved surface along the circumference of the pillar <NUM>.

In addition, as more clearly illustrated in <FIG>, a plurality of ring-shaped gaskets <NUM> may be fitted on an outer circumferential surface of the pillar <NUM> so as to be sealed between the outer circumferential surface of the pillar <NUM> and an inner circumferential surface of the passage <NUM>.

Therefore, when the gas is in a normal pressure range before a gas is generated inside the pouch <NUM>, the gate <NUM> shields the passage <NUM> by the elastic force of the spring <NUM> as illustrated in the left drawing of <FIG>.

And, when the gas is generated inside the pouch <NUM> to increase in pressure inside the pouch <NUM>, the gas pressure overcomes the elastic force of the spring <NUM> to push the gate <NUM>, and thus, the gas is introduced into the chamber <NUM> as illustrated in the right drawing of <FIG> and then is discharged to the outside through the discharge hole <NUM>. Here, an opening valve pressure of the gate <NUM>, at which the gate is opened, may be variously set by adjusting the elastic force of the spring <NUM>.

Furthermore, when the gate <NUM> is opened by frictional force generated between the gate <NUM> and the body <NUM> and frictional force generated between the gasket <NUM> and the body <NUM>, the opening may be maintained even though a pressure is slightly lower than the applied pressure to efficiently discharge the gas (for example, when the gas pressure is <NUM> Mpa, if the gate is opened, the gas is discharged to the outside to decrease in gas pressure, and thus, the gate is set so as not to be closed even when the gas pressure is <NUM> Mpa, but to be closed at a pressure of about <NUM> Mpa.

Also, a lubricant and vacuum grease may be additionally applied to the contact portion between the body <NUM> and the gate <NUM> to reduce sealing properties and the frictional force, and the lubricant and vacuum grease may be selected from materials that do not react with the electrolyte.

In this embodiment, a valve to which a blocking film <NUM> that shields a passage <NUM> in a body <NUM> of the valve <NUM> according to the first embodiment is additionally attached.

<FIG> is a cross-sectional view (left) illustrating a state in which a blocking film is mounted at an inlet-side of a passage and a cross-sectional view (right) illustrating a state in which the blocking film is separated from a mounted position according to a second embodiment of the present invention.

Referring to <FIG>, the blocking film <NUM> for preventing an electrolyte from being permeated may be mounted on an inlet-side of the passage <NUM> in the body <NUM>.

The blocking film <NUM> is provided to prevent a gas and electrolyte from being unnecessarily introduced into the passage <NUM> before an internal pressure of the pouch <NUM> increases.

The blocking film <NUM> may be configured to be torn or separated from the mounted position when a gas is generated inside the pouch <NUM> to increase in the internal pressure.

The blocking film <NUM> is not limited to a specific material as long as the material does not cause a chemical reaction with the electrolyte, but is preferably a material that is capable of being easily torn according to a change in pressure. Alternatively, even if the material is not sensitive to the pressure change, the blocking film <NUM> may be mounted by adjusting sensitivity of an adhesive <NUM> by which the blocking film <NUM> adheres to prevent the blocking film <NUM> from being separated.

The blocking film <NUM> according to the present invention is manufactured as a thin film made of polypropylene or polytetrafluoroethylene.

Also, a pressure sensitive adhesive may be used as the adhesive <NUM> adhering to the blocking film.

In the present invention having the configuration as described above, when the gas is generated inside the pouch <NUM>, and the pressure of the gas overcomes elastic force of a spring <NUM>, the gate <NUM> may be opened to discharge to a discharge hole <NUM>, thereby efficiently preventing swelling from occurring and preventing moisture and the foreign substances from being introduced from the outside of the valve <NUM>.

An O-ring <NUM> may be mounted at a point of the hook protrusion, at which the gate <NUM> is seated, to prevent the electrolyte from leaking.

Furthermore, the blocking film <NUM> may be mounted on an inlet-side of a passage <NUM> to fundamentally block introduction of the electrolyte into the valve <NUM> when the pressure inside the pouch <NUM> is in the normal range.

The blocking film <NUM> may be made of a material that does not cause a chemical reaction with the electrolyte to prevent the electrolyte from being deteriorated in performance.

In the valve <NUM> of the present invention, an auxiliary discharge hole <NUM> may be formed in an opposite side of the discharge hole <NUM> to prevent air resistance from adversely affecting sliding of the valve <NUM>.

Claim 1:
A secondary battery in which an electrode assembly and an electrolyte are inserted and injected into a pouch, and an edge of the pouch is sealed to form a sealing portion, the secondary battery comprising:
a valve (<NUM>) fixed to the sealing portion so that one end thereof faces the inside of the pouch, and the other end thereof faces the outside of the pouch,
wherein the valve (<NUM>) comprises:
a body (<NUM>) forming a passage (<NUM>) having opened one end facing the inside of the pouch and provided with a chamber (<NUM>) connected to the passage (<NUM>), wherein a discharge hole (<NUM>) communicating with the outside is formed in the chamber (<NUM>);
a gate (<NUM>) seated on a hook protrusion forming a boundary between the passage (<NUM>) and the chamber (<NUM>) to open or close the passage (<NUM>); and
a spring (<NUM>) mounted to apply elastic force in a direction in which the gate (<NUM>) is closed,
wherein the gate (<NUM>) is configured to be opened to discharge the gas through the discharge hole (<NUM>) when a gas is generated inside the pouch so that a pressure of the gas overcomes the elastic force of the spring (<NUM>), and
wherein an auxiliary discharge hole (<NUM>) is formed so that when the gate (<NUM>) slides inside the chamber (<NUM>), air within the chamber (<NUM>) is discharged,
wherein the auxiliary discharge hole (<NUM>) is formed at an opposite side of the discharge hole (<NUM>) with the gate (<NUM>) therebetween.