Secondary battery and manufacturing method thereof

Abstract

The secondary battery of the present invention includes an electrode assembly having electrode leads connected thereto, a pouch having a receiving portion that receives the electrode assembly with the tips of the electrode leads extended to the outside, and a sealing portion formed along the edge of the receiving portion and sealing the receiving portion, and a gas exhaust portion provided in the pouch that exhausts gas from the inside of the pouch to the outside and blocks the inflow of moisture from the outside to the inside of the pouch, the gas exhaust portion including a breathable gas-permeable film that exhausts gas inside the receiving portion to the outside, and a moisture-absorbing material that absorbs moisture that passes through the gas-permeable film to block the inflow of moisture from the outside to the inside of the pouch.

Description

[Technical field]

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0126429, filed September 28, 2020, Korean Patent Application No. 10-2020-0126430, filed September 28, 2020, and Korean Patent Application No. 10-2021-0125592, filed September 23, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a secondary battery having a structure that allows gas inside a pouch to be discharged and blocks the inflow of moisture outside the pouch, and a method for manufacturing the same. [Background technology]

[0003] In general, a secondary battery is a battery that can be charged and discharged, unlike a primary battery which cannot be charged. Such secondary batteries are widely used in the field of advanced electronic devices such as phones, notebook computers, and camcorders.

[0004] The secondary batteries are classified into a can-type secondary battery in which an electrode assembly is housed in a metal can and a pouch-type secondary battery in which an electrode assembly is housed in a pouch, and the pouch-type secondary battery includes an electrode assembly, an electrode lead connected to an electrode tab of the electrode assembly, and a pouch that houses the electrode assembly with the tip of the electrode lead extended to the outside.

[0005] However, a secondary battery having the above structure has a problem in that if gas pressure increases inside the pouch due to overcharging or short circuiting, the pouch may vent, causing an explosion or fire. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been invented to solve the above problems, and aims to provide a secondary battery and a manufacturing method thereof, which includes a gas exhaust section that exhausts only gas generated inside the pouch to the outside, thereby preventing the pouch from being vented and causing an explosion or fire, and in particular, which can block the inflow of moisture into the pouch and prevent a deterioration in the performance of the secondary battery.

[0007] Another object of the present invention is to provide a secondary battery and a manufacturing method thereof that can improve the safety of the secondary battery by including a gas exhaust section between an electrode lead, which is highly likely to vent, and a seal section. [Means for solving the problem]

[0008] In order to achieve the above-mentioned objects, a secondary battery of the present invention includes an electrode assembly having an electrode lead connected thereto, a pouch having a receiving portion for receiving the electrode assembly with a tip of the electrode lead extended to the outside, and a seal portion formed along an edge of the receiving portion and sealing the receiving portion, and a gas exhaust portion provided in the pouch for exhausting gas from inside to outside the pouch and blocking inflow of moisture from outside to inside the pouch, wherein the gas exhaust portion may include a gas permeable film having breathability for exhausting gas inside the receiving portion to the outside, and a moisture absorbing material for absorbing moisture passing through the gas permeable film to block inflow of moisture from outside to inside the pouch.

[0009] The gas exhaust portion may be provided between the electrode lead and the seal portion.

[0010] The gas exhaust portion may be provided in the seal portion.

[0011] An adhesive film may be provided between the gas exhaust portion and the seal portion to seal the gas exhaust portion and the seal portion.

[0012] The adhesive film may be made of a breathable material.

[0013] The adhesive film may be provided to surround the entire outer periphery of the gas permeable film so that the gas exhaust portion is not exposed to the outside.

[0014] The adhesive film may have a lower breathability than the gas permeable film.

[0015] The moisture absorbing material may be disposed on an outer surface of the gas permeable film.

[0016] The moisture absorbing material is provided so as to be contained within the gas permeable film.

[0017] The gas permeable film may be made of a thermoplastic resin, and the moisture absorbing material may be made of an oxide that absorbs moisture.

[0018] Meanwhile, a method for manufacturing a secondary battery of the present invention may include the steps of: (a) preparing a pouch including an upper case and a lower case, the upper case including an upper housing surface and an upper sealing surface, and the lower case including a lower housing surface and a lower sealing surface; (b) arranging the upper case and the lower case in correspondence with each other, and then arranging an electrode assembly having an electrode lead connected thereto in an accommodating portion formed by connecting the upper housing surface and the lower housing surface; (c) manufacturing a gas exhaust portion including a gas permeable film having breathability and a moisture absorbing material that absorbs moisture passing through the gas permeable film; (d) arranging the gas exhaust portion between the upper sealing surface of the upper case and the lower sealing surface of the lower case; and (e) heat-sealing the upper sealing surface and the lower sealing surface to form a seal portion.

[0019] In the step (d), the gas exhaust portion may be provided between the upper sealing surface and the lower sealing surface corresponding to the electrode lead.

[0020] After manufacturing the gas exhaust part in step (c), the method may further include a step of attaching an adhesive film to the outside of the gas exhaust part.

[0021] In step (c), the moisture absorbing material may be provided on the outside of the gas permeable film.

[0022] In step (c), the moisture absorbing material may be contained within the gas permeable film during the production of the gas permeable film. Effect of the Invention

[0023] The secondary battery of the present invention is characterized in that it includes a gas exhaust section between the electrode lead and the sealed part of the pouch, and the gas exhaust section includes a gas permeable film and a moisture absorbing material. That is, by including the gas exhaust section between the electrode lead, which is highly likely to vent, and the sealed part of the pouch, the safety of the secondary battery can be improved.

[0024] In other words, the gas exhaust section can stably exhaust gas from the inside to the outside of the pouch through the gas permeable film, and can absorb moisture that passes through the gas permeable film through the moisture absorbing material, thereby blocking the inflow of moisture into the inside of the pouch. [Brief description of the drawings]

[0025] [Figure 1] 1 is an exploded perspective view showing a secondary battery according to a first embodiment of the present invention; [Diagram 2] 1 is a plan view showing a secondary battery according to a first embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view taken along line AA shown in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line BB shown in FIG. [Diagram 5] 4 is a cross-sectional view showing a second example of the moisture absorbing material of the secondary battery according to the first embodiment of the present invention. FIG. [Figure 6]FIG. 4 is a cross-sectional view showing a third example of the moisture absorbing material of the secondary battery according to the first embodiment of the present invention. [Figure 7] 3 is a flowchart showing a method for manufacturing a secondary battery according to the first embodiment of the present invention. [Figure 8] FIG. 2 is a perspective view showing a method for manufacturing a secondary battery according to the first embodiment of the present invention, illustrating a pouch preparation step. [Figure 9] FIG. 2 is a perspective view showing an electrode assembly arrangement step in the method for manufacturing a secondary battery according to the first embodiment of the present invention. [Figure 10] FIG. 2 is a diagram showing a method for manufacturing a secondary battery according to the first embodiment of the present invention, illustrating a gas exhaust portion manufacturing step. [Figure 11] FIG. 2 is a perspective view showing a method for manufacturing a secondary battery according to the first embodiment of the present invention, illustrating a gas exhaust part arranging step. [Figure 12] FIG. 2 is a perspective view showing a method for manufacturing a secondary battery according to the first embodiment of the present invention, illustrating a step of manufacturing a secondary battery having a gas exhaust unit. [Figure 13] FIG. 4 is a cross-sectional view showing a secondary battery according to a second embodiment of the present invention. [Figure 14] FIG. 4 is a cross-sectional view showing a secondary battery according to a third embodiment of the present invention. [Figure 15] FIG. 11 is a plan view showing a secondary battery according to a fourth embodiment of the present invention. [Figure 16] 16 is a cross-sectional view taken along line CC shown in FIG. 15. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present invention may be realized in various forms and is not limited to the embodiments described herein. In the drawings, in order to clearly explain the present invention, parts that are not related to the description are omitted, and similar parts are designated by similar reference numerals throughout the specification.

[0027] [Secondary battery according to the first embodiment of the present invention] The secondary battery 100 according to the first embodiment of the present invention has a structure that allows gas to be discharged from the inside of the pouch to the outside, and blocks the inflow of moisture from the outside to the inside of the pouch.

[0028] That is, as shown in FIG. 1 and FIG. 2, the secondary battery 100 according to the first embodiment of the present invention includes an electrode assembly 110 to which an electrode lead 130 is coupled, a pouch 120 that houses the electrode assembly 110 with the tip of the electrode lead 130 extended to the outside, and a gas exhaust portion 140 that is provided between the electrode lead 130 and the pouch 120 and exhausts gas from the inside of the pouch 120 to the outside and blocks the inflow of moisture from the outside to the inside of the pouch 120,

[0029] electrode assembly The electrode assembly 110 has a structure in which a plurality of electrodes are vertically stacked with separators interposed therebetween, and the electrodes are provided with electrode tabs to which electrode leads 130 are coupled.

[0030] Meanwhile, the electrodes include first and second electrodes, the electrode tabs include a first electrode tab provided on the first electrode and a second electrode tab provided on the second electrode, and the electrode lead 130 includes a first electrode lead coupled to the first electrode tab and a second electrode lead coupled to the second electrode tab.

[0031] Here, the first electrode is a positive electrode and the second electrode is a negative electrode, although it goes without saying that the opposite is also possible.

[0032] Pouch The pouch 120 includes a receiving portion 120a that receives the electrode assembly 110 and an electrolyte (not shown) when the electrode lead 130 is extended to the outside, and a sealing portion 120b that is formed along the edge of the receiving portion 120a and seals the receiving portion 120a.

[0033] Meanwhile, the pouch 120 includes an upper case 121 and a lower case 122. The upper case 121 includes an upper receiving surface 121a having a receiving groove formed therein for receiving an upper portion of the electrode assembly 110, and an upper sealing surface 121b formed along an edge of the upper receiving surface 121a. The lower case 122 includes a lower receiving surface 122a having a receiving groove formed therein for receiving a lower portion of the electrode assembly 110, and a lower sealing surface 122b formed along an edge of the lower receiving surface 122a.

[0034] In the pouch 120 having such a structure, the upper receiving surface 121a and the lower receiving surface 122a are connected vertically to form a receiving portion 120a that receives the entire electrode assembly 110, and the upper sealing surface 121b and the lower sealing surface 122b are heat-sealed to form a sealing portion 120b that seals the receiving portion 120a.

[0035] Here, the tip of the electrode lead 130 is drawn out to the outside through a seal part 120b located at one edge of the receiving part 120a. That is, the tip of the electrode lead 130 is drawn out to the outside through a gap between an upper seal surface 121b and a lower seal surface 122b.

[0036] Meanwhile, the seal portion 120b from which the electrode lead 130 is pulled out has a weaker seal strength than the other seal portions 120b, so that when the gas pressure inside the pouch increases significantly, the gap between the electrode lead 130 and the seal portion 120b is vented first, which may cause an explosion or fire.

[0037] In order to solve the above problems, the secondary battery 100 according to the first embodiment of the present invention includes a gas exhaust part 140 provided in the pouch 120, which exhausts gas from the inside of the pouch 120 to the outside and blocks the inflow of moisture from the outside to the inside of the pouch 120, and the gas exhaust part 140 can prevent the pouch from exploding or catching fire.

[0038] 2, the gas exhaust unit 140 includes a gas permeable film 141 having breathability, which is provided between the electrode lead 130 and the sealing unit 120b and exhausts gas inside the receiving unit 120a to the outside, and a moisture absorbing material 142 which absorbs moisture passing through the gas permeable film 141 and blocks the inflow of moisture from the outside to the inside of the pouch 120. As a result, the gas generated inside the pouch can be exhausted through the gas exhaust unit 140, thereby improving safety. In particular, the gas exhaust unit 140 includes a moisture absorbing material, which blocks the inflow of moisture from the outside to the inside of the pouch 120 and allows only the gas inside the pouch to be exhausted.

[0039] The gas exhaust unit 140 will now be described in more detail.

[0040] Gas exhaust section 3 and 4, gas exhaust part 140 is provided between electrode lead 130 and sealing part 120b, and has a structure for exhausting gas from the inside of pouch 120 to the outside and blocking the inflow of moisture from the outside to the inside of pouch 120. That is, gas exhaust part 140 has a structure for exhausting only gas inside the pouch to the outside.

[0041] As an example, the gas exhaust portion 140 includes a gas permeable film 141 that allows gas to be exhausted from the inside of the pouch 120 to the outside, and a moisture absorbing material 142 that absorbs moisture that flows into the inside of the pouch through the gas permeable film 141.

[0042] The gas permeable film 141 is provided between the electrode lead 130 and the sealing portion 120b. Preferably, the gas permeable film 141 is provided between the electrode lead 130 and the sealing portion 120b in a form surrounding the electrode lead 130, and seals the electrode lead 130 and the gas exhaust portion 140. In particular, both side ends of the gas permeable film 141 are positioned to protrude to the inside and outside of the sealing portion 120b. As a result, the area of ​​the gas permeable film 141 exposed to the inside and outside of the pouch 120 can be increased to enhance gas exhausting power and minimize clogging of the gas permeable film 141 by foreign matter.

[0043] The gas permeable film 141 having such a structure may be made of a synthetic resin having breathability, and may preferably be made of a thermoplastic resin. For example, the gas permeable film may be made of polypropylene. This allows gas generated inside the pouch 120 to be discharged to the outside. In particular, the gas permeable film 141 is provided in a form surrounding the electrode lead 130, and allows gas inside the pouch to be effectively discharged before a vent is generated between the electrode lead and the seal portion.

[0044] The moisture absorbing material 142 is made of a material that absorbs moisture and is provided on the outer surface of the gas permeable film 141. By being provided on the gas permeable film 141, the moisture absorbing material 142 absorbs and removes moisture that flows from the outside of the pouch 120 through the gas permeable film 141. That is, the moisture absorbing material 142 blocks the flow of moisture from the outside of the pouch 120 to the inside.

[0045] That is, the moisture absorbing material 142 is in the form of a film, and is made of an oxide that absorbs moisture, and is provided in a form surrounding the outer periphery of the gas permeable film 141 .

[0046] Here, the moisture absorbing material 142 is made of any one of CaO, LiCl, Si3N4, SiO2, Al2O3, mullite, ZrO2, Y2O3, MgO, BeO, TiB2, TiC, HfC, and ZrC. Here, the moisture absorbing material may further include a getter.

[0047] Meanwhile, since it is difficult to use the getter alone, it can be used as a composite material including a binder. That is, a composite material in which a getter and a binder are combined at a set ratio can be manufactured into a film. Meanwhile, the getter refers to a material that absorbs gas or moisture remaining in a vacuum object.

[0048] 5, a plurality of film-shaped moisture absorbing materials 142 may be disposed at regular intervals on the outer side of the gas permeable film 141 along the length direction of the electrode lead 130. Thus, the plurality of moisture absorbing materials can block the inflow of moisture in multiple stages.

[0049] 6, a film-like moisture absorbing material 142 may be further disposed between the electrode lead 130 and the gas permeable film 141. In particular, a plurality of the film-like moisture absorbing materials 142 may be disposed at regular intervals along the length direction of the electrode lead 130 between the electrode lead 130 and the gas permeable film 141. This makes it possible to effectively absorb and remove the inflow of moisture from the inside and outside of the gas permeable film 141, and in particular, to block the inflow of moisture in multiple stages.

[0050] Meanwhile, the moisture absorbing material 142 may be provided so as to be contained inside the gas permeable film, thereby minimizing an increase in the thickness of the gas exhaust portion and obtaining the effect of exhausting gas and blocking the inflow of moisture. In particular, the moisture absorbing material 142 may be contained so as to be dispersed throughout the inside of the gas permeable film 141, or may be contained in the form of a lump in the center of the gas permeable film 141.

[0051] Meanwhile, the moisture absorbing material 142 may be embedded in the gas permeable film 141 so as not to be exposed to the outside. That is, by preventing the moisture absorbing material 142 from being exposed to the outside, it is possible to prevent the electrolyte from being contaminated by the moisture absorbing material.

[0052] Meanwhile, an adhesive film 143 is provided between the gas exhaust part 140 and the sealing part 120b, and the adhesive film 143 can increase the binding force and sealing force between the gas exhaust part 140 and the sealing part 120b.

[0053] On the other hand, the adhesive film 143 can be made of either polypropylene (PP) or polyethylene (PE).

[0054] That is, the adhesive film 143 is for adhering and sealing the gas permeable film having the moisture absorbing material between the electrode lead and the sealing part, and is made of a synthetic resin having air permeability and is provided in a form surrounding the gas permeable film having the moisture absorbing material. As a result, the adhesive film 143 can seal the gap between the gas permeable film 141 and the sealing part 120b, and can exhaust the gas inside the pouch to the outside together with the gas permeable film.

[0055] Here, the adhesive film 143 has lower breathability than the gas permeable film 141. This is to minimize weakening of the adhesive strength of the adhesive film 143 due to gas emission and to allow gas inside the pouch to be emitted together with the gas permeable film 141.

[0056] Meanwhile, the adhesive film 143 is provided in a form surrounding the entire outer periphery of the gas permeable film so that the moisture absorbing material is not exposed to the outside, thereby protecting the moisture absorbing material and preventing the electrolyte inside the pouch from being contaminated by the moisture absorbing material.

[0057] In particular, the gas discharge force passing through the gas permeable film 141 via the adhesive film 143 can be adjusted.

[0058] Therefore, the secondary battery 100 according to the first embodiment of the present invention includes the gas exhaust part 140 between the electrode lead and the seal part, so that the gas inside the pouch can be effectively exhausted and the inflow of moisture from the outside to the inside of the pouch can be effectively blocked, thereby improving safety.

[0059] Hereinafter, a method for manufacturing a secondary battery according to a first embodiment of the present invention will be described.

[0060] [Method of manufacturing a secondary battery according to the first embodiment of the present invention] The manufacturing method of the secondary battery according to the first embodiment of the present invention includes, as shown in FIGS. 7 to 12, (a) a pouch preparation step, (b) an electrode assembly arrangement step, (c) a gas exhaust portion manufacturing step, (d) a gas exhaust portion arrangement step, and (e) a secondary battery completion step in which a gas exhaust portion is formed.

[0061] (a) Step 8, in step (a), a pouch 120 having an upper case 121 and a lower case 122 is prepared. Here, the upper case 121 includes an upper receiving surface 121a and an upper sealing surface 121b, and the lower case 122 includes a lower receiving surface 122a and a lower sealing surface 122b.

[0062] Meanwhile, the upper accommodating surface 121a and the lower accommodating surface 122a are arranged vertically to form an accommodating portion 120a that accommodates the electrode assembly, and the upper sealing surface 121b and the lower sealing surface 122b are joined to form a sealing portion 120b that seals the accommodating portion 120a.

[0063] (b) Step In step (b), referring to FIG. 9, the upper case 121 and the lower case 122 are arranged in a corresponding relationship, and then the electrode assembly 110 having the electrode lead 130 connected thereto is placed in the receiving portion 120a formed by connecting the upper receiving surface 121a and the lower receiving surface 122a.

[0064] (c) Step In step (c), referring to FIG. 10, a gas exhaust part 140 is manufactured, which includes a gas permeable film 141 having breathability and a moisture absorbing material 142 that absorbs moisture, and an adhesive film 143 having adhesive strength is attached to the outside of the gas exhaust part.

[0065] For example, the gas exhaust part 140 is composed of two gas exhaust films 140a and 140b in which a gas permeable film 141 having breathability and a moisture absorbing material 142 that absorbs moisture are laminated in order, and an adhesive film 143 is attached to the outer surfaces of the gas exhaust films 140a and 140b.

[0066] That is, the gas permeable film 141, the moisture absorbing material 142, and the adhesive film 143 have a three-layer laminate structure.

[0067] Here, the adhesive film 143 has an area larger than the gas permeable film 141 and the moisture absorbing material 142, so that the adhesive film 143 can completely surround the gas permeable film 141 and the moisture absorbing material 142 when the gas exhaust portion is formed.

[0068] In addition, the moisture absorbing material 142 may have an area smaller than that of the gas permeable film 141 and the adhesive film 143 so that the moisture absorbing material 142 is embedded between the gas permeable film 141 and the adhesive film 143 .

[0069] Meanwhile, the moisture absorbing material 142 is made of any one of CaO, LiCl, Si3N4, SiO2, Al2O3, mullite, ZrO2, Y2O3, MgO, BeO, TiB2, TiC, HfC, and ZrC, which have excellent moisture absorbing power.

[0070] On the other hand, the adhesive film 143 has air permeability, and has air permeability lower than that of the gas permeable film 141 .

[0071] (d) Step In the step (d), referring to FIG. 11, a gas exhaust part is disposed between the upper sealing surface of the upper case and the lower sealing surface of the lower case.

[0072] More preferably, in step (d), the gas exhaust films 140a and 140b are symmetrically disposed on the upper and lower surfaces of the electrode lead 130 located between the upper sealing surface 121b and the lower sealing surface 122b, with the gas permeable film 141 facing the electrode lead 130.

[0073] Meanwhile, the step (d) may further include a process of bonding the gas-emission films 140a, 140b disposed on the upper and lower surfaces of the electrode lead 130. Here, in the gas-emission film bonding process, the gas-emission films 140a, 140b are bonded by compression using heat and pressure. Meanwhile, the gas-emission film bonding process may be performed simultaneously with the step (e) or separately from the step (e).

[0074] In the present invention, a step of bonding the gas-releasing films 140a and 140b is performed separately from the step (e) as one embodiment.

[0075] Gas exhaust film bonding process In the gas exhaust film bonding process, the gas exhaust film 140a disposed on the upper and lower surfaces of the electrode lead 130 is compressed to manufacture the gas exhaust part 140.

[0076] That is, gas permeable films 141 arranged on the upper and lower surfaces of the electrode lead 130 are bonded to surround the electrode lead 130, moisture absorbing materials 142 arranged on the upper and lower surfaces of the electrode lead 130 are bonded to surround the gas permeable films, and adhesive films 143 arranged on the upper and lower surfaces of the electrode lead 130 are bonded to seal the gap between the electrode lead and the seal portion.

[0077] Here, since the adhesive film 143 has an area larger than that of the gas permeable film 141, it can surround the entire gas permeable film, thereby preventing the moisture absorbing material 142 from being exposed to the outside.

[0078] (e) Step 12, in step (e), the upper sealing surface 121b and the lower sealing surface 122b are heat-sealed to form a sealing portion 120b. At this time, the gas exhaust portion 140 located on the electrode lead 130 is also joined to the sealing portion 120b together with the sealing portion 120b, thereby sealing the gap between the electrode lead 130 and the sealing portion 120b.

[0079] When step (e) is completed as described above, a secondary battery 100 including a gas exhaust portion as shown in FIG. 1 can be manufactured.

[0080] Thereafter, when the gas pressure rises inside the secondary battery 100, the gas inside the pouch is discharged to the outside through the gas discharge portion provided between the electrode lead and the seal portion, thereby preventing the pouch from venting. At this time, the adhesive film 143 is also breathable, so that it is possible to discharge a part of the gas inside the pouch. This makes it possible to prevent the gas pressure inside the secondary battery from rising significantly, and as a result, the safety of the secondary battery can be improved.

[0081] Here, moisture from outside the pouch 120 may flow in through the gas exhaust portion, but the moisture can be absorbed by the moisture absorbing material 142 contained in the gas exhaust portion 140, thereby preventing the moisture from flowing into the inside of the pouch.

[0082] In the following description of other embodiments of the present invention, the same reference numerals will be used for components having the same functions as those in the above-described embodiment, and duplicated explanations will be omitted.

[0083] [Secondary battery according to a second embodiment of the present invention] 13, the secondary battery 100 according to the second embodiment of the present invention includes a gas exhaust part 140 provided between the electrode lead 130 and the seal part 120b of the pouch 120, and the gas exhaust part 140 includes a gas permeable film 141 and a moisture absorbing material 142. Here, an adhesive film 143 is attached to the outside of the gas exhaust part.

[0084] The adhesive film 143 includes end surfaces 143a provided on both sides of the gas exhaust portion 140 exposed to the inside and outside of the pouch 120, and a peripheral surface 143b provided on the remaining surface of the gas exhaust portion 140.

[0085] Here, the end surface 143a has a smaller thickness than the peripheral surface 143b in order to increase the breathability compared to the peripheral surface 143b. That is, the thickness α of the peripheral surface 143b is formed to be thicker than the thickness β of the end surface 143a. As a result, the peripheral surface 143b increases the sealing force between the electrode lead and the seal part, and the end surface 143a prevents the moisture absorbing material from being exposed to the outside and adjusts the amount of gas discharged from the inside of the pouch to the outside.

[0086] [Secondary battery according to a third embodiment of the present invention] 14, a secondary battery 100 according to a third embodiment of the present invention includes a gas exhaust part 140, which includes a gas permeable film 141 and a moisture absorbing material 142. An adhesive film 143 is attached to the outer side of the gas exhaust part 140.

[0087] Here, the moisture absorbing material 142 may be contained throughout the gas permeable film 141 .

[0088] That is, in step (c) of the method for manufacturing a secondary battery according to the first embodiment of the present invention, the moisture absorbing material 142 is contained in the gas permeable film 141 during its manufacture, so that the gas permeable film 141 containing the moisture absorbing material 142 can be manufactured.

[0089] More specifically, the moisture absorbing material 142 and the gas permeable film 141 are mixed to produce a composite material, and the composite material is processed into a film to produce the gas permeable film 141 containing the moisture absorbing material 142.

[0090] Therefore, the secondary battery 100 according to the third embodiment of the present invention can absorb and remove moisture passing through the gas permeable film by the moisture absorbing material, and can also discharge gas inside the pouch by the moisture absorbing material, thereby greatly increasing the gas discharge ability.

[0091] [Secondary battery according to a fourth embodiment of the present invention] As shown in Figures 15 and 16, the secondary battery 100 according to the fourth embodiment of the present invention includes an electrode assembly 110 having an electrode lead connected thereto, a pouch 120, and a gas exhaust portion 140, and the gas exhaust portion 140 includes a gas permeable film 141 and a moisture absorbing material 142.

[0092] Here, the gas exhaust part 140 is provided in the sealed part 120b of the pouch 120 where no electrode lead is located.

[0093] That is, the gas exhaust part 140 is disposed between the upper seal surface 121b and the lower seal surface 122b, which do not have electrode leads, and is coupled together when the upper seal surface 121b and the lower seal surface 122b are heat-sealed.

[0094] Meanwhile, an adhesive film 143 is interposed between the gas exhaust part 140 and the sealing part 120 b , and the adhesive film 143 is attached to the outside of the gas exhaust part 140 .

[0095] Therefore, the secondary battery 100 according to the fourth embodiment of the present invention can be provided with a gas exhaust part even in a seal part having no electrode lead, and as a result, gas generated inside the secondary battery can be effectively exhausted, and the inflow of moisture from the outside to the inside of the secondary battery can be blocked.

[0096] The scope of the present invention will be defined by the appended claims rather than the above detailed description, and various embodiments are possible within the meaning and scope of the claims and their equivalents. [Explanation of symbols]

[0097] 100 Secondary battery 110 Electrode assembly 120 pouches 130 Electrode Lead 140 Gas exhaust section 141 Gas permeable film 142 Moisture absorbing materials 143 Adhesive Film

Claims

1. an electrode assembly having an electrode lead connected thereto; a pouch including a receiving portion for receiving the electrode assembly with the tip of the electrode lead being pulled out to the outside, and a seal portion formed along an edge of the receiving portion for sealing the receiving portion; a gas exhaust section provided in the pouch so as to surround the electrode lead, for exhausting gas from the inside of the pouch to the outside and for blocking inflow of moisture from the outside to the inside of the pouch; the gas exhaust section includes a gas permeable film having air permeability for exhausting gas inside the storage section to the outside, and a moisture absorbing material for absorbing moisture passing through the gas permeable film to block the inflow of moisture from the outside to the inside of the pouch, The moisture absorbing material is contained throughout the interior of the gas permeable film, The gas permeable film is made of a thermoplastic resin, The moisture absorbing material is made of an oxide that absorbs moisture.

2. The secondary battery according to claim 1 , wherein the gas exhaust portion is provided between the electrode lead and the seal portion.

3. The secondary battery according to claim 1 , wherein the gas exhaust portion is provided in the sealing portion.

4. 4. The secondary battery according to claim 2, further comprising an adhesive film provided between the gas exhaust portion and the seal portion for sealing the gap between the gas exhaust portion and the seal portion.

5. The secondary battery according to claim 4 , wherein the adhesive film is made of a breathable material.

6. The secondary battery according to claim 5 , wherein the adhesive film is provided so as to surround the entire outer circumferential surface of the gas permeable film so that the gas exhaust portion is not exposed to the outside.

7. An electrode assembly having an electrode lead connected thereto; a pouch including a receiving portion for receiving the electrode assembly with the tip of the electrode lead being pulled out to the outside, and a seal portion formed along an edge of the receiving portion for sealing the receiving portion; a gas exhaust section provided in the pouch so as to surround the electrode lead, for exhausting gas from the inside of the pouch to the outside and for blocking inflow of moisture from the outside to the inside of the pouch; the gas exhaust section includes a gas permeable film having air permeability for exhausting gas inside the storage section to the outside, and a moisture absorbing material for absorbing moisture passing through the gas permeable film to block the inflow of moisture from the outside to the inside of the pouch, The moisture absorbing material is contained throughout the interior of the gas permeable film, The gas exhaust portion is provided between the electrode lead and the seal portion, or is provided in the seal portion, an adhesive film that seals the gas exhaust portion and the seal portion is provided between the gas exhaust portion and the seal portion; The adhesive film is made of a breathable material, A secondary battery, wherein the adhesive film has a lower air permeability than the gas permeable film.

8. An electrode assembly having an electrode lead connected thereto; a pouch including a receiving portion for receiving the electrode assembly with the tip of the electrode lead being pulled out to the outside, and a seal portion formed along an edge of the receiving portion for sealing the receiving portion; a gas exhaust section provided in the pouch so as to surround the electrode lead, for exhausting gas from the inside of the pouch to the outside and for blocking the inflow of moisture from the outside to the inside of the pouch; the gas exhaust section includes a gas permeable film having air permeability for exhausting gas inside the storage section to the outside, and a moisture absorbing material for absorbing moisture passing through the gas permeable film to block the inflow of moisture from the outside to the inside of the pouch, The moisture absorbing material is contained throughout the interior of the gas permeable film, The moisture absorbing material is provided on an outer surface of the gas permeable film.

9. 8. The secondary battery according to claim 1, wherein the moisture absorbing material is provided so as to be contained inside the gas permeable film.

10. A method for producing a secondary battery according to claim 1, comprising the steps of: (a) preparing the pouch comprising an upper case and a lower case, the upper case comprising an upper receiving surface and an upper sealing surface, and the lower case comprising a lower receiving surface and a lower sealing surface; (b) arranging the upper case and the lower case in a corresponding relationship, and then arranging the electrode assembly having the electrode leads coupled thereto in the receiving portion formed by connecting the upper receiving surface and the lower receiving surface; (c) manufacturing the gas exhaust portion including the gas permeable film having air permeability and the moisture absorbing material that absorbs moisture passing through the gas permeable film, the gas exhaust portion being disposed so as to surround the electrode lead; (d) disposing the gas exhaust portion between the upper sealing surface of the upper case and the lower sealing surface of the lower case; (e) heat fusing the upper sealing surface and the lower sealing surface to form the seal; In the step (c), the moisture absorbing material is contained throughout the inside of the gas permeable film during the production of the gas permeable film.

11. The method of claim 10, wherein in step (d), the gas exhaust portion is provided between the upper sealing surface and the lower sealing surface corresponding to the electrode lead.

12. The method for manufacturing a secondary battery according to claim 10 or 11, further comprising the step of attaching an adhesive film to an outer side of the gas exhaust part after manufacturing the gas exhaust part in the step (c).

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