Patent Description:
Depending on the shape of the battery case, the secondary battery is classified into a cylindrical battery and a prismatic battery in which an electrode assembly is embedded in a cylindrical or prismatic metal can, and a pouch-type battery in which the electrode assembly is embedded in a pouch-type case made of an aluminum laminate sheet. Among them, the cylindrical battery has the advantage of having a relatively large capacity and structural stability.

In addition, the electrode assembly built into the battery case is a power generating device capable of charging and discharging with a stacked structure of a positive electrode/a separator/a negative electrode. The electrode assembly is classified into a jelly-roll type in which a long sheet-type positive electrode and negative electrode are wound with a separator interposed therebetween, and a stack-type in which a plurality of positive and negative electrodes with a predetermined size are sequentially stacked with a separator interposed therebetween. Among them, the jelly-roll type electrode assembly has advantages of being easy to manufacture and having a high energy density per weight.

The cylindrical secondary battery is manufactured by accommodating a jelly-roll type electrode assembly in a cylindrical case, injecting an electrolyte into the cylindrical case, and then coupling a cap having an electrode terminal formed at an open top of the case.

Meanwhile, a large amount of gas may be generated in the process of activating the secondary battery, and the large amount of gas generated may deteriorate the performance of the secondary battery and cause safety problems.

In general, pouch-type secondary batteries and prismatic secondary batteries remove gases in advance by adding an activation gas discharging process during the manufacturing process. However, on the other hand, the cylindrical secondary battery has a problem in that an activation gas discharging process cannot be used due to structural characteristics of maintaining an airtight seal after electrolyte injection.

Cylindrical secondary batteries in which activation gas is not separately discharged in the manufacturing process through the activation gas discharging process may easily increase in internal pressure during actual use, which may cause a major accident such as battery explosion.

Therefore, there is a need to develop a cylindrical secondary battery having a new structure that can solve the problem of increase in the internal pressure of the cylindrical battery.

<CIT> <CIT> discloses a cylindrical battery which includes a power generation element, a bottom cylindrical battery case for housing the power generation element, and an assembly sealing plate for sealing the opening portion of the battery case, wherein the assembly sealing plate has a hermetic space, at least a part of which is constituted by a current cut off mechanism.

<CIT> discloses a secondary battery according to the preamble of independent claim <NUM>.

Therefore, the present invention has been devised to solve the above problems, and it is directed to provide a secondary battery capable of easily removing an activation gas generated inside a battery can in which an electrode assembly is accommodated during the process of activating or using the secondary battery.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the exemplary embodiments of the present invention. In addition, the objectives and advantages of this invention can be easily understood to be realized by the means and combinations indicated in the scope of the patent claims.

According to the present invention, a secondary battery including: an electrode assembly; a battery can in which the electrode assembly is accommodated; a cap assembly including an upper cap plate forming a positive terminal and disposed above the battery can; and a gasket surrounding the rim of the cap assembly and interposed between the battery can and the cap assembly, wherein the secondary battery further includes a member disposed between the cap assembly and the gasket wherein the member is porous in order to discharge gas generated in the battery can to the outside is provided.

In addition, the cap assembly further includes a safety vent coupled to a lower part of the upper cap plate and has a shape that protrudes downward, and the safety vent may protrude upward and break when the pressure inside the battery can rises above a set pressure.

In addition, the cap assembly further includes a current blocking element having at least a part of an upper part electrically connected to the upper cap plate and a lower part electrically connected to the electrode assembly, and the current blocking element may block electrical connection with at least one among the upper cap plate and the electrode assembly when the pressure inside the battery can rises above a set pressure.

Specifically, the porous member may be coupled to at least one among an inner circumferential surface of the gasket facing the cap assembly and an outer circumferential surface of the cap assembly facing the gasket.

More specifically, the porous member may be additionally interposed on the outer circumferential surface of the gasket opposite to the battery can.

According to an exemplary embodiment, the porous member may be a porous film surrounding the rim of the gasket or the cap assembly.

According to another exemplary embodiment, the porous member may be a porous coating layer coated on the rim of the gasket or the cap assembly.

According to another exemplary embodiment, the porous member may be a porous ring extending along the circumference of the gasket and the cap assembly.

Specifically, the porous film, the porous coating layer, and the porous ring may each have a thickness of <NUM> to <NUM>.

In addition, the porous member may have a pore size of <NUM> to <NUM>, and an air permeability at <NUM> kPa of <NUM><NUM>/cm<NUM>*s to <NUM><NUM>/cm<NUM>*s.

Meanwhile, the gasket may include a side support part facing the side part of the cap assembly and a horizontal bending part extending from upper and lower ends of the side support part and bent toward the cap assembly to contact upper and lower surfaces of the cap assembly, wherein at least one or more porous rings may be disposed between the horizontal bending part of the gasket and the upper surface of the cap assembly and between the horizontal bending part of the gasket and the lower surface of the cap assembly, respectively.

On the other hand, a gas discharge passage connected to the porous ring may be formed between an inner circumferential surface of the gasket and an outer circumferential surface of the cap assembly opposite to the inner circumferential surface of the gasket.

Specifically, a venting groove may be formed on the inner circumferential surface of the gasket extending entirely or partially throughout the inner circumferential surface of the gasket, wherein the gas discharge passage may be formed between the venting groove and the outer circumferential surface of the cap assembly.

More specifically, the venting grooves formed by partial extension may be formed spaced apart along the inner circumferential surface of the gasket by a predetermined distance.

In addition, a concave part may be formed spaced apart along the outer circumferential surface of the cap assembly by a predetermined distance, wherein the gas discharge passage may be formed between the concave part and the inner circumferential surface of the gasket.

According to the present invention, it is possible to prevent a phenomenon in which the pressure inside a secondary battery increases due to the gas generated in the secondary battery and the external shape of the battery can is deformed.

In addition, according to the present invention, it is possible to effectively prevent accidents such as an explosion of a secondary battery due to an increase in internal pressure of the secondary battery.

Hereinafter, the detailed configuration of the present invention will be described in detail with reference to the accompanying drawings and various embodiments. The exemplary embodiments described below are illustrative to help understanding of the present invention, and the accompanying drawings are not drawn to scale and the dimensions of some components may be exaggerated to help understanding of the present invention.

Since the present invention may have various changes and various forms, specific exemplary embodiments are illustrated in the drawings and described in detail in the text.

<FIG> is an exploded perspective view and a partial cross-sectional view of a secondary battery of the present invention.

Referring to <FIG>, a secondary battery according to the present invention includes an electrode assembly <NUM>, a battery can <NUM>, a cap assembly <NUM>, and a gasket <NUM>.

The electrode assembly <NUM> is accommodated in the battery can <NUM> with a positive electrode plate and a negative electrode plate disposed with a separator interposed therebetween. Here, the electrode assembly <NUM> is also called a jelly-roll because it is wound and arranged in a jelly roll shape. The electrode plates of the electrode assembly <NUM> are formed as a structure in which an active material slurry is applied on a current collector, and the slurry may be typically formed by stirring an active material, a conductor, a binder, a plasticizer, etc. in a solvent. It is preferable that a non-coated part to which slurry is not applied is present at the beginning and end of the current collector in the direction in which the electrode plates are wound, and an electrode lead <NUM> corresponding to each electrode plate may be attached to the non-coated part. In general, a positive lead is attached to the upper part of the electrode assembly <NUM> to be electrically connected to an upper cap plate <NUM>, and a negative lead is attached to the lower part of the electrode assembly <NUM> to be electrically connected to the bottom of the battery can <NUM>.

Meanwhile, an electrically insulating plate <NUM> may be disposed on the upper part of the electrode assembly <NUM>, and the insulating plate <NUM> serves to insulate between the electrode assembly <NUM> and the upper cap plate <NUM>.

The battery can <NUM> is made of a lightweight conductive metal material such as aluminum, stainless steel, or an alloy thereof, and has a cylindrical structure with an open part with the upper part open and a sealed bottom part opposite thereto. An electrolyte is accommodated together with the electrode assembly <NUM> in the inner space of the battery can <NUM>.

A beading part <NUM> for mounting the cap assembly <NUM> may be formed on the upper part of the battery can <NUM>. The beading part <NUM> is indented inside between the cap assembly <NUM> and the electrode assembly <NUM>, and more specifically, the lower end part of the cap assembly <NUM> is settled and fixed to the upper part of the indented inner surface of the beading part <NUM>, and the upper end part of the electrode assembly <NUM> may be positioned on the lower part of the indented inner surface of the beading part <NUM>.

<FIG> shows a battery can <NUM> included in the secondary battery of the present invention and a modified example thereof.

Referring to <FIG>, a beading part <NUM> indented inwardly on the upper part of the battery can <NUM> extends along the circumference of the battery can <NUM>. However, the battery can <NUM> of the present invention is not limited thereto, and the beading part <NUM> may not be formed in the battery can <NUM> of the present invention, as shown in <FIG>. In this case, a protruding part (not shown) may be formed on the inner surface of the battery can <NUM> protruding with a certain length so that the cap assembly <NUM> can be settled thereon.

For the convenience of understanding, the present invention will be described based on the battery can <NUM> on which the beading part <NUM> is formed.

After the cap assembly <NUM> is inserted into and settled inside the battery can <NUM>, the upper end of the battery can <NUM> is bent toward the cap assembly <NUM> to form a crimping part <NUM>.

The crimping part <NUM> serves to press and fix the upper surface of the cap assembly <NUM> to prevent the upper cap assembly <NUM> from escaping to the outside, and at the same time to completely seal the secondary battery from the outside. Specifically, the crimping part <NUM> is formed by the uppermost end of the battery can <NUM> covering and pressing the upper surface of the gasket <NUM> surrounding the rim part of the upper cap plate <NUM>.

The cap assembly <NUM> of the present invention is inserted into the battery can <NUM> and placed on upper part of the battery can <NUM>.

The cap assembly <NUM> includes an upper cap plate <NUM> disposed on the upper part to form a positive electrode terminal. More specifically, the upper cap plate <NUM> is disposed in a form protruding upward from the uppermost part of the cap assembly <NUM>, and forms a positive terminal. Accordingly, the upper cap plate <NUM> electrically connects the secondary battery to the outside.

The upper cap plate <NUM> may be formed of a metal material such as stainless steel or aluminum in consideration of strength and conductivity.

As illustrated, the upper cap plate <NUM> has a shape in which a center part is protruded, and a side surface of the protruding center part has an inclined surface formed along the edge of the protruding center part.

The edge part of the upper cap plate <NUM> may be designed to maintain level with the bottom of the battery can <NUM>, but is not limited thereto.

The diameter of the upper cap plate <NUM> is preferably the same as or slightly smaller than the inner diameter of the battery can <NUM> so that the upper cap plate can be inserted into the battery can <NUM>.

A gas hole <NUM> through which gas can be discharged may be formed in the upper cap plate <NUM>. The gas hole <NUM> may be formed, for example, on a side surface of the protruding center part of the upper cap plate <NUM>, that is, on an inclined surface. Specifically, a safety vent <NUM> blocking an inner space connected to the gas hole <NUM> from the electrode assembly <NUM> may be further provided inside the cap assembly <NUM>.

The safety vent <NUM> is coupled to the lower part of the upper cap plate <NUM>, and has a shape that protrudes downward.

The safety vent <NUM> serves to discharge gas to the outside by protruding upward and breaking when the pressure inside the secondary battery rises above a set pressure.

In a usual condition, the gas generated inside the secondary battery cannot be discharged through the gas hole <NUM> due to the safety vent <NUM>. However, when an abnormal phenomenon occurs in the electrode assembly <NUM> and an excessive amount of gas is generated and the gas pressure exceeds a certain value, the safety vent <NUM> breaks to discharge the gas filled inside to the outside, and the secondary battery explosion can be prevented.

As described above, the safety vent <NUM> is configured to break when the gas pressure inside the secondary battery increases to a certain level. For example, the safety vent may break when the gas pressure inside the secondary battery is 12kgf/cm<NUM> to 25kgf/cm<NUM>.

The cap assembly <NUM> of the present invention may further include a current blocking element <NUM>.

The current blocking element <NUM> is a component of the cap assembly <NUM> in which at least a part of the upper part of the current blocking element <NUM> is connected to the lower part of the safety vent <NUM>. More specifically, the current blocking element <NUM> is disposed between the safety vent <NUM> and the electrode assembly <NUM>.

The current blocking element <NUM> may block electrical connection with at least one among the upper cap plate <NUM> and the electrode assembly <NUM> when the pressure inside the battery can <NUM> rises above a set pressure. Specifically, in a normal state, the lower protruding part of the safety vent <NUM> is in contact with the current blocking element <NUM>, but when the internal pressure (gas pressure) increases due to gas generation and the shape of the safety vent <NUM> is reversed, the electrical connection between the current blocking element <NUM> and the safety vent <NUM> may be blocked. Also, the lower part of the current blocking element <NUM> may be connected to the electrode assembly <NUM> through an electrode lead <NUM>. Therefore, in a normal state, the current blocking element <NUM> allows a current flow between the electrode assembly <NUM> and the safety vent <NUM>. The current blocking element <NUM> may be deformed or damaged along with the safety vent <NUM> due to an increase in internal pressure of the secondary battery, and as a result, electrical connection with the electrode assembly <NUM> may be blocked.

The cap assembly <NUM> of the present invention may further include a safety element (not shown) provided in the lower part of the upper cap plate <NUM>. Preferably, the safety element is interposed between the upper cap plate <NUM> and the safety vent <NUM>, and electrically connects the upper cap plate <NUM> and the safety vent <NUM>. The safety element is to block the flow of current inside the battery due to overheating of the battery, and may be formed of, for example, a PTC (Positive Temperature Coefficient) element.

As shown in <FIG>, the gasket <NUM> surrounds the rim of the cap assembly <NUM> and is interposed between the battery can <NUM> and the cap assembly <NUM>.

The gasket <NUM> may be made of a material having electrical insulation, impact resistance, elasticity, and durability, for example, a polyolefin or a polypropylene.

The gasket <NUM> insulates the cap assembly <NUM> from being electrically connected to the battery can <NUM>. In addition, the gasket <NUM> prevents the electrolyte stored in the battery can <NUM> from leaking through a tiny gap between the cap assembly <NUM> and the battery can <NUM>.

The gasket <NUM> may be largely divided into a side support part 120a and a horizontal bending part 120b. Specifically, the side support part 120a faces the side of the cap assembly <NUM>, and the horizontal bending part 120b extends from the upper and lower end parts of the side support part 120a and is bent toward the cap assembly <NUM> to be in contact with the upper and lower surfaces of the cap assembly <NUM>. The side support part 120a of the gasket <NUM> supports and surrounds the side surface of the cap assembly <NUM>, and the horizontal bending part 120b extending from the upper and lower ends of the side support part 120a presses each upper surface and lower surface of the rim of the cap assembly <NUM> to completely adhere to the cap assembly <NUM>.

The porous member <NUM> is disposed between the gasket <NUM> and the upper cap plate <NUM> to discharge gas generated in the battery can <NUM> to the outside.

The porous member <NUM> includes a porous material to selectively discharge the gas generated inside the secondary battery to the outside.

The material of the porous member <NUM> includes pores, and is made of a material capable of selectively passing only gas while obstructing the flow of liquid through the pores. For example, the porous member <NUM> may be made of porous polytetrafluoroethylene (PTFE) material. However, it is preferable that the size of the pores of the porous member <NUM> is designed to be sufficiently small so as to pass only gaseous body such as gas and not pass the electrolyte inside the secondary battery to the outside. For example, the size of the pores is <NUM> to <NUM>, and the air permeability at 1kPa is <NUM> to <NUM><NUM>/cm<NUM>*s.

The porous member <NUM> may be independently manufactured in the form of a film or a circular ring. Alternatively, the porous member may be manufactured by being coated on the surface of another member. More specifically, the porous member <NUM> of the present invention may be in the form of at least one among a porous film, a porous coating layer, and a porous ring 130a. Here, the thickness of the porous film, the porous coating layer, and the porous ring 130a is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>, respectively. When the thickness of the porous member <NUM> having various shapes is less than <NUM>, a large amount of gas cannot smoothly move around, and when the thickness of the porous member <NUM> exceeds <NUM>, the sealing power of the liquid electrolyte inside the secondary battery may be lowered, and the structural stability of the secondary battery may be deteriorated.

The secondary battery of the present invention may have various embodiments depending on the shape, structure, and attachment position of the porous member <NUM>, the gasket <NUM>, and the cap assembly <NUM>.

<FIG> relates to a configuration related to a secondary battery according to the first embodiment, <FIG> relates to a configuration related to a secondary battery according to the second embodiment, <FIG> relates to a configuration related to a secondary battery according to the third embodiment, <FIG> relate to configurations related to a secondary battery according to the fourth embodiment, <FIG> relate to configurations related to a secondary battery according to the fifth embodiment, <FIG> relate to configurations related to a secondary battery according to the sixth embodiment, and <FIG> relate to configurations related to a secondary battery according to the seventh embodiment.

The porous member <NUM> included in the secondary battery according to the first embodiment may be a porous film in the form a film capable of being attached to the surface of the cap assembly <NUM> and the surface of the gasket <NUM> so that it can be interposed between the cap assembly <NUM> and the gasket <NUM>.

The porous member <NUM> is interposed between the gasket <NUM> and the cap assembly <NUM>. More specifically, the porous member <NUM> may be coupled to at least one among an inner circumferential surface of the gasket <NUM> facing the cap assembly <NUM> and an outer circumferential surface of the cap assembly <NUM> facing the gasket <NUM>.

The porous member <NUM> may be attached and coupled to the inner circumferential surface of the gasket <NUM> and extend along the circumferential direction of the gasket <NUM>. In this case, the gasket <NUM> is coupled to the rim of the cap assembly <NUM> in a state in which the porous member <NUM> is attached to the inner circumferential surface of the gasket <NUM>.

<FIG> is a perspective view and a partial cross-sectional view of a cap assembly <NUM> included in a secondary battery according to the first embodiment of the present invention and a gasket <NUM> coupled thereto.

According to the illustration, the porous member <NUM> is interposed between the cap assembly <NUM> and the gasket <NUM>. Here, the cap assembly <NUM> and the gasket <NUM> are spaced apart from each other by a predetermined distance by the porous member <NUM>.

The porous member <NUM> is disposed in contact with the entire inner circumferential surface of the side support part 120a and the horizontal bending part 120b of the gasket <NUM>. In this case, as illustrated, the porous member <NUM> may be formed by protruding a predetermined length from the end part of the horizontally bending part 120b of the gasket <NUM>.

The porous member <NUM> serves as a path for gas to move between the cap assembly <NUM> and the gasket <NUM>. That is, the gas frequently generated from the battery can <NUM> moves through the porous member <NUM> interposed between the cap assembly <NUM> and the gasket <NUM>, and is discharged to the outside by leaving between the upper cap plate <NUM> of the cap assembly <NUM> and the gasket <NUM>.

The porous member <NUM> included in the secondary battery according to the second embodiment is additionally formed on the outer circumferential surface of the gasket <NUM>. In this case, like the first embodiment, the porous member <NUM> is porous film in the form of a film attachable to the surfaces of the cap assembly <NUM> and the gasket so that it can be interposed between the cap assembly <NUM> and the gasket <NUM> and between the battery can <NUM> and the gasket <NUM>.

Specifically, the porous member <NUM> is formed on the outer circumferential surface of the gasket <NUM> opposite to the battery can <NUM> and extends along the circumferential direction of the gasket <NUM>.

<FIG> is a perspective view and a partial cross-sectional view of a cap assembly <NUM> included in a secondary battery according to the second embodiment of the present invention and a gasket <NUM> coupled thereto.

According to the illustration, the porous member <NUM> is formed by being attached to the inner and outer circumferential surfaces of the gasket <NUM>, respectively. In this case, since the gas generated inside the secondary battery can move through two paths, gas discharging efficiency can be further increased. That is, the gas generated from time to time in the battery can <NUM> moves through the porous member <NUM> interposed between the cap assembly <NUM> and the gasket <NUM> and the porous member <NUM> interposed between the battery can <NUM> and the gasket <NUM>, and is discharged to the outside by leaving between the cap assembly <NUM> and gasket <NUM> and between the battery can <NUM> and the gasket <NUM>, respectively.

The porous member <NUM> included in the secondary battery according to the third embodiment is coated on the edge of the gasket <NUM> or the cap assembly <NUM>. For example, the porous member <NUM> may be coated on the entire surface of the gasket <NUM>, instead of being made of a film in a separate process and attached to the cap assembly <NUM>, the gasket <NUM>, etc..

<FIG> is a perspective view and a partial cross-sectional view of a cap assembly <NUM> included in a secondary battery according to the third embodiment of the present invention and a gasket <NUM> coupled thereto.

According to the illustration, the porous member <NUM> covers the entire surface of the gasket <NUM>. In this case, since it is possible to omit the process of manufacturing the porous member <NUM> separately and attaching it to the cap assembly <NUM>, the gasket <NUM>, etc., manufacturing efficiency can be increased. In addition, gas generated inside the secondary battery can move through two paths as in the second embodiment, and since the porous member <NUM> is formed in a wider area than in the second embodiment, gas discharging efficiency can be improved.

The porous member <NUM> of the present invention may be a ring-shaped porous ring 130a extending along the circumferences of the gasket <NUM> and the cap assembly <NUM>.

<FIG> is a perspective view and a partial cross-sectional view of a porous ring 130a of the present invention.

The porous ring 130a may have a circular cross-section as shown, but may also have a polygonal shape such as a triangle or a quadrangle.

The ring-shaped porous member <NUM> as described above does not need to be manufactured with the shape and structure of the cap assembly <NUM> or the gasket <NUM> in mind as in the first and the second embodiments, and as in the third embodiment, a process of coating the porous member <NUM> on the surface of the gasket <NUM> may also be omitted. Therefore, the manufacturing efficiency of the secondary battery can be improved. In addition, since a plurality of porous rings 130a having various diameters can be installed on the cap assembly <NUM>, there is an advantage in that it is easy to control the gas discharge performance.

At least one or more porous rings 130a may be disposed between the horizontal bending part 120b of the gasket <NUM> and the upper surface of the cap assembly <NUM> and between the horizontal bending part 120b and the lower surface of the cap assembly <NUM>, respectively. For example, two or more porous rings 130a may be disposed on the upper and lower surfaces of the cap assembly <NUM>, respectively.

<FIG> is a perspective view and a partial cross-sectional view of a cap assembly <NUM> included in a secondary battery according to the fourth embodiment of the present invention and a gasket <NUM> coupled thereto.

As illustrated, the porous ring 130a may be interposed between the cap assembly <NUM> and the gasket <NUM> at the upper and lower parts of the cap assembly <NUM>. Although not illustrated, the porous ring 130a may be interposed between the side surface of the cap assembly <NUM> and the side support part 120a of the gasket <NUM>.

A gas discharge passage connected to the porous ring 130a is formed between the inner circumferential surface of the gasket <NUM> and the outer circumferential surface of the cap assembly <NUM> opposite to the inner circumferential surface of the gasket <NUM>. Specifically, the gasket <NUM> and the cap assembly <NUM> maintains a state in which they are spaced apart in a predetermined distance as the porous ring 130a is interposed therebetween, and the above distance forms a gas discharge passage through which gas can move. Since the gas discharge passage selectively moves gas by the porous ring 130a, electrolyte and the like inside the secondary battery is not discharged to the outside through the gas discharge passage.

Meanwhile, when the porous ring 130a is not interposed between the side surface of the cap assembly <NUM> and the side support part 120a of the gasket <NUM>, there may be a problem in that the gas discharge passage is blocked by the side surface of the cap assembly <NUM> coming into close contact with the side support part 120a of the gasket <NUM>. Therefore, in this case, the cap assembly <NUM> may be designed to be spaced apart from the gasket <NUM> by a predetermined distance. For example, the diameter of the cap assembly <NUM> may be smaller than the diameter of the inner circumferential surface of the gasket <NUM>.

When the secondary battery of the present invention includes the porous ring 130a, the gasket <NUM> may have a venting groove a formed on the inner circumferential surface and extending along the inner circumferential surface, or the venting groove a may be formed partially thereof.

<FIG> is a perspective view and a cross-sectional view of a gasket <NUM> included in a secondary battery according to the fifth embodiment of the present invention.

According to the illustration, the venting groove a is formed on the inner circumferential surface of the gasket <NUM> and extending along the circumferential direction of the gasket <NUM>.

The venting groove a is formed to allow the gas to move more smoothly by widening the gap between the side surface of the cap assembly <NUM> and the side support part 120a of the gasket <NUM>.

The venting groove a is preferably formed on the side support part 120a of the gasket <NUM>.

<FIG> is a cross-sectional view and a partially enlarged view of a secondary battery according to the fifth embodiment of the present invention.

Even if the side surface of the cap assembly <NUM> and the side support part 120a of the gasket <NUM> are in close contact with each other, a certain gas movement spacing is formed by the venting groove a as shown. That is, a gas discharge passage is formed between the venting groove a and the outer circumferential surface of the cap assembly <NUM>.

However, in order for the gas to move, it is preferable that the size of the venting groove a be larger than the thickness of the cap assembly <NUM>.

When the secondary battery of the present invention includes the porous ring 130a, venting grooves a may be formed by being spaced at a predetermined distance along the inner circumferential surface of the gasket <NUM>.

<FIG> is a perspective view and a cross-sectional view of a gasket <NUM> included in a secondary battery according to the sixth embodiment of the present invention.

According to the illustration, the venting groove a is formed by being spaced apart at a certain distance along the inner circumferential surface of the gasket <NUM>. In this case, among the inner circumferential surface of the gasket <NUM>, the space between the venting grooves a adheres to and supports the side surface of the cap assembly <NUM> inserted inward, and the space where the venting groove a is formed is spaced apart from the side surface of the cap assembly <NUM> by a predetermined distance to form a gas discharge passage.

<FIG> is a cross-sectional view and a partially enlarged view of a secondary battery according to the sixth embodiment of the present invention.

According to the illustration, the secondary battery according to the sixth embodiment moves gas through the venting groove a similarly to the fifth embodiment. Since the space of the venting groove a of the gasket <NUM> included in the secondary battery according to the sixth embodiment is relatively small compared to the venting groove a included in the gasket <NUM> of the secondary battery of the fifth embodiment, the gas discharging efficiency may be slightly lowered, but the effect of fixing to the side surface of the cap assembly <NUM> by the gasket <NUM> is more outstanding.

However, similar to the fifth embodiment, in order for the gas to move, it is preferable that the size of the venting groove a be larger than the thickness of the cap assembly <NUM>.

When the secondary battery of the present invention includes the porous ring 130a, the cap assembly <NUM> may include a concave part b spaced apart from each other at a certain distance along the outer circumferential surface. This feature is the same even when a plurality of configurations is included in the cap assembly <NUM>. For example, when the cap assembly <NUM> includes an upper cap plate <NUM>, a safety vent <NUM>, etc., the concave part b is formed in both the upper cap plate <NUM> and the safety vent <NUM>. In this case, in the upper cap plate <NUM> and the safety vent <NUM>, the positions of the concave part b formed in the upper cap plate <NUM> and the concave part b formed in the safety vent <NUM> coincide with each other.

<FIG> is an exploded perspective view of a cap assembly <NUM> of a secondary battery according to the seventh embodiment of the present invention.

According to the illustration, the concave part b spaced apart from each other in a certain distance is formed on the rims of the upper cap plate <NUM> and the safety vent <NUM> bonded to the lower part of the upper cap plate <NUM>, respectively.

The safety vent <NUM> is coupled to the lower part of the upper cap plate <NUM> by adjusting the position of the concave part b such that the position of the concave part b of the upper cap plate <NUM> coincides with the concave part (b) of the safety vent <NUM>.

<FIG> is a cross-sectional view and a partially enlarged view of a secondary battery according to the seventh embodiment of the present invention.

According to the illustration, among the side surfaces of the cap assembly <NUM>, the space between the concave parts b is in close contact with the side support part 120a of the gasket <NUM>, and the space where the concave part b is formed becomes a gas discharge passage through which the gas moves.

In the cap assembly <NUM> included in the secondary battery according to the seventh embodiment, the concave part (b) includes a gas discharge passage between the inner circumferential surfaces of the gasket <NUM>, and similar to the sixth embodiment, the gas is discharged to the outside through a gas discharge passage formed by being spaced apart at a predetermined distance along the circumferential direction of the cap assembly <NUM> or the gasket <NUM>.

Claim 1:
A secondary battery comprising:
an electrode assembly (<NUM>);
a battery can (<NUM>) in which the electrode assembly (<NUM>) is accommodated;
a cap assembly (<NUM>) comprising an upper cap plate (<NUM>) forming a positive terminal, and disposed above the battery can (<NUM>); and
a gasket (<NUM>) surrounding the rim of the cap assembly (<NUM>) and interposed between the battery can (<NUM>) and the cap assembly (<NUM>), and
a member (<NUM>) disposed between the cap assembly (<NUM>) and the gasket (<NUM>),
characterized in that the member (<NUM>) is porous in order to discharge gas generated in the battery can (<NUM>) to the outside.