KR101011807B1 - Secondary Battery with Top Sealed Portion of Improved Structure - Google Patents

Abstract

According to the present invention, an electrode assembly having a cathode / separation membrane / cathode structure is embedded in a battery case of a laminate sheet including a resin layer and a metal layer, and an insulating film ('') is disposed on an upper surface and a lower surface of an electrode lead connected to the electrode assembly. Electrode lead film ') is heat-sealed to the battery case in the manufacturing process of the battery, the electrode lead or the electrode lead film of the heat-sealing portion is composed of inorganic particles and the electrode lead and the electrode lead film can directly contact each other Provided is a secondary battery having a structure in which a predetermined pattern having a plurality of openings is formed.

Description

Secondary Battery with Top Sealed Portion of Improved Structure

1 is an exploded perspective view of a general structure of a conventional pouch type secondary battery;

FIG. 2 is a vertical cross-sectional view partially enlarged of an upper part of a battery case coupled to a cathode lead in a state in which positive electrode tabs are densely assembled in a state in which the secondary battery of FIG. 1 is assembled;

3 is a vertical cross-sectional view of a structure in which an inorganic particle pattern is formed between an electrode lead film and an electrode lead of an upper part of a battery case according to one embodiment of the present invention;

4 is an enlarged view of the upper sealing portion A of FIG. 3;

FIG. 5 is an enlarged plan view of only an electrode lead portion in which a pattern of a network structure is formed in FIG. 3; FIG.

6 is a schematic view of an electrode lead formed with an inorganic particle pattern.

The present invention relates to a pouch type secondary battery including an upper sealing part of an improved structure, and more particularly, an electrode assembly having a cathode / separation membrane / cathode structure is embedded in a battery case of a laminate sheet including a resin layer and a metal layer. The insulating film ("electrode lead film") interposed on the upper and lower surfaces of the electrode lead connected to the electrode assembly is thermally fused to the battery case during the manufacturing process of the battery. The surface of the film is composed of inorganic particles and relates to a secondary battery having a structure in which a predetermined pattern is formed in which a plurality of openings are formed in which the electrode lead and the electrode lead film can directly contact each other.

As technology development and demand for mobile devices increase, the demand for batteries as energy sources is rapidly increasing, and accordingly, many studies on batteries that can meet various demands have been conducted.

Representatively, there is a high demand for square secondary batteries and pouch type secondary batteries that can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries. Demand for lithium secondary batteries such as lithium ion polymer batteries is high.

FIG. 1 is a schematic exploded perspective view of a general structure of a conventional representative pouch type secondary battery.

Referring to FIG. 1, the pouch type secondary battery 10 may include an electrode assembly 30, electrode tabs 40 and 50 extending from the electrode assembly 30, and electrodes welded to the electrode tabs 40 and 50. And a battery case 20 accommodating the leads 60 and 70 and the electrode assembly 30.

The electrode assembly 30 is a power generator in which a positive electrode and a negative electrode are sequentially stacked in a state where a separator is interposed therebetween, and, for example, welding is performed on electrode tabs 40 and 50 extending to the positive electrode and the negative electrode. Leads 60 and 70 are electrically connected to each other, and the end portions of the electrode leads 60 and 70 are embedded in the battery case 20 while being exposed to the outside. In addition, electrode lead films 80 are attached to upper and lower portions of the electrode leads 60 and 70 in order to increase the degree of sealing with the battery case 20 and to secure an electrical insulation state.

The battery case 20 is composed of an outer coating layer 20a made of ONy (stretched nylon film), a barrier layer 20b made of aluminum, and an inner sealant layer 20c made of CPP (non-stretched polypropylene film), A hot melt layer (not shown) is coated on the edge of the inner sealant layer 20c, so that the body and the cover of the battery case 20 can be tightly fixed by heat and pressure from a heat sealer (not shown). .

FIG. 2 is a partially enlarged view schematically illustrating an upper portion of the upper part of the battery case coupled to the positive electrode lead by being coupled in a dense form in the assembled state of the secondary battery of FIG. 1. In FIG. 2, only the anode lead portion is illustrated, for example, for convenience of description, and such an anode structure may be easily applied to the cathode structure.

Referring to FIG. 2, the plurality of positive electrode tabs 40 protruding from the positive electrode current collector (not shown) of the electrode assembly are integrally coupled to each other and connected to the positive electrode lead 60, for example, by welding. The positive lead 60 is heat-sealed together with the electrode lead film 80 in the upper sealing portion 21 of the battery case 20 with the ends opposite to the positive electrode tabs 40 exposed. The two electrode lead films 80 attached to the anode lead 60 overlap each other with the same length on both sides of the anode lead 60, and thus the upper end 81 and the lower end of the electrode lead film 80 ( 82 each have a mutually coincident structure. Generally, about 80 to 100 μm thick PP or PE is used as the electrode lead film 80, and is integrated with the battery case 20 in the upper sealing part 21 during heat fusion.

In this battery structure, the upper sealing portion 21 is formed by a heat fusion method of heating the upper surface and the lower surface of the battery case 20 to a predetermined jig (not shown) while heating at a predetermined temperature or more. However, since the anode lead 60 made of metal quickly releases heat during the heat fusion process of the battery case 20, it is not easy to accurately control the temperature required for the heat fusion, and furthermore, the thickness of the anode lead 60. As a result, the corresponding portions are subjected to higher pressure than other sealing portions, and thus, uniform heat welding tends not to be achieved. Although the inner surface shape of the thermal welding jig is formed in consideration of the thickness of the anode lead 60, thermal fusion is not performed at each position or relatively high pressure is applied in the pressing process. In this case, the desired sealing portion cannot be obtained.

Specifically, in the heat fusion process of the battery case 20, when a relatively high heat and / or pressure is applied to a portion corresponding to the positive electrode lead 60, the electrode lead film (80) attached to the positive electrode lead 60 ) Is damaged and the anode lead 60 is exposed. In addition, when the inner sealant layer (FIG. 1: 20c) is damaged in the battery case 20 and the aluminum layer (FIG. 1: 20b), which is an intermediate layer, is exposed and comes into contact with the electrode lead, a short circuit occurs, thereby greatly reducing safety. Therefore, a problem occurs that the life of the battery is shortened.

In this regard, Korean Patent No. 512552 discloses that an inner surface layer of a pouch case is formed of a composite material including both organic and inorganic materials in a pouch-type lithium secondary battery, and thus, even though the organic material is melted, insulation functions by the inorganic material. A technique has been proposed to maintain and prevent shorting of the pouch case and electrode tabs. That is, the patent is a technique for adding an inorganic material such as an inorganic powder to a sealant layer made of an organic material such as CPP in general, so as to maintain insulation by the inorganic material even if the organic material is lost in the heat fusion process for sealing.

Therefore, by applying the technology of the patent, it is possible to first consider a method for solving the problems in the thermal fusion process as described above by adding an inorganic material to the electrode lead film. However, an electrode lead film made of a composite material in which an inorganic material is dispersed in an organic material has a disadvantage in that it exhibits low bonding strength to an electrode lead which is metallic when thermally fused.

The pouch type battery has a risk of leakage of electrolyte solution to this area due to the decrease in thermal fusion bonding strength of the upper sealing portion of the battery due to continuous charge / discharge operation and external force such as vibration and dropping. In particular, due to the expansion and contraction that occurs during charging and discharging of the battery and the movement of internal components of the battery case due to external force, the upper sealing part is more likely to be separated than the other sealing parts, and electrolyte may leak through the separated part. have.

Therefore, there is a limit in applying the contents of the patent to the electrode lead film as it is, and there is a need for improved and supplemented technology.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

The inventors of the present application, after in-depth studies and various experiments on the secondary battery, when forming a predetermined pattern including inorganic particles between the electrode lead and the electrode lead film, the electrode leads to the electrode lead during heat sealing for sealing While maintaining the excellent adhesion of the electrode lead film for the same time, it was confirmed that the problem caused by damage to the electrode lead film and the like in the heat fusion process can be solved fundamentally, and came to complete the present invention.

Accordingly, in the secondary battery according to the present invention, an electrode assembly having a cathode / separation membrane / cathode structure is embedded in a battery case of a laminate sheet including a resin layer and a metal layer, respectively, on the upper and lower surfaces of an electrode lead connected to the electrode assembly. The interposed insulating film ('electrode lead film') is thermally fused to the battery case during the manufacturing process of the battery, and the electrode lead or electrode lead is composed of inorganic particles on the surface of the electrode lead or the electrode lead film among the heat fusion sites. The film has a structure in which a predetermined pattern in which a plurality of openings are formed which can directly contact each other is located.

That is, in the battery structure in which the electrode lead film is attached to the upper and lower surfaces of the electrode lead to increase the sealing degree with the battery case and to secure the electrical insulation state, the inorganic lead particles include insulating inorganic particles between the electrode lead and the electrode lead film. It consists of a structure in which a predetermined pattern made of a material is located.

Therefore, by the above pattern, even when the electrode lead film or the inner sealant layer of the battery case is damaged during high temperature and high pressure heat fusion in the battery assembly process, the pattern serves as a kind of support to prevent the electrode lead from being completely exposed. By preventing contact between the electrode lead and the metal barrier layer of the battery case, the safety of the battery can be improved. In addition, since a plurality of openings are formed in the pattern, the electrode lead film may be partially melted and directly adhered to the electrode lead in the heat fusion process, so that the thermal bonding is high even though the pattern is located between the electrode lead and the electrode lead film. It can exert a bonding force.

The secondary battery according to the present invention may be preferably applied to a pouch type secondary battery in which an electrode assembly is built in a pouch type case of a laminate sheet including a metal layer and a resin layer, for example, an aluminum laminate sheet.

The electrode lead film is not particularly limited as long as it has a material having insulation and heat adhesion (heat adhesion), and preferably has excellent insulation and heat adhesion and has low hygroscopicity to suppress invasion of the electrolyte solution and expands with the electrolyte solution. Or non-eroded polypropylene film (CPP) -based resins may be used.

The pattern is preferably formed by applying inorganic particles on the electrode lead or the electrode lead film prior to heat fusion, for example, on the corresponding surface of the film attached to the electrode lead in the manufacturing process of the electrode lead film. The pattern may be formed or, conversely, the pattern may be formed on the upper and lower surfaces of the electrode lead.

In one preferred example, the pattern may be formed by applying a printing paste including inorganic particles and a binder by screen printing. Specifically, after the inorganic particles are added to the binder and stirred to prepare a printing paste, the upper and lower surfaces of the electrode leads or the surfaces where the electrode lead films are in contact with the electrode leads at the sealing portions where the electrode leads and the electrode lead films are fused. The pattern may be formed by printing a paste on a screen printing method and then drying the paste.

The pattern may have various shapes, and preferably, may have a network structure, a honeycomb structure, a stripe structure, or the like. When the electrode lead film and the electrode lead are thermally fused, between the openings of the network structure or the honeycomb structure, or between the stripes of the stripe structure, as mentioned above, the electrode lead film is thermally fused in direct contact with the electrode lead.

The thickness of the pattern preferably has a size of 30 to 90% based on the thickness of the electrode lead film. If the thickness of the pattern is too thick, the pattern may partially protrude to the surface of the electrode lead film in the heat fusion process, thereby decreasing the sealability with the battery case. On the contrary, if the pattern is too small, the effect of the present invention is reduced, which is not preferable.

In addition, the size of the openings in the pattern is preferably 60 to 95% based on the total surface area of the pattern. If the openings are too small, the contact area between the electrode leads and the electrode lead films may become small, resulting in a decrease in mutual bonding force. If the size of the float is too large, it may be difficult to form a pattern having a predetermined thickness, which is undesirable.

The inorganic particles may be, for example, one or two or more mixtures selected from the group consisting of alumina, silica, and titanium dioxide, but are not limited thereto.

In one preferred embodiment, the surface of the pattern may be of a hydrophobic structure to prevent the hydrophilic electrolyte from penetrating into the pattern. Such a structure can be achieved by treating the inorganic particles with a silane compound so that the pattern shows hydrophobicity, and specifically, by combining a silane compound showing hydrophobicity at the molecular end of the hydrophilic inorganic particles included in the pattern by chemical reaction, the inorganic material This can be accomplished by converting the particles into hydrophobic.

The secondary battery according to the present invention may be preferably used as a unit cell of a medium-large battery pack providing a high output and a large capacity, in particular, due to its excellent life and safety.

Accordingly, the present invention also provides a medium-large battery module including a plurality of secondary batteries as a unit cell, and a high-output, high-capacity medium-large battery pack including one or more such medium-large battery modules.

The medium-large battery pack is required as a high-power, large-capacity electricity such as an electric vehicle, a hybrid electric vehicle, an electric bicycle, an electric motorcycle, and is particularly preferable as a power source of a device to which a lot of external force such as vibration and shock is applied.

Since the configuration of the medium-large battery module and the battery pack and a method of manufacturing the same are well known in the art, a detailed description thereof will be omitted herein.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

3 schematically illustrates a vertical cross-sectional shape of a structure in which an inorganic particle pattern is formed between an electrode lead film and an electrode lead of an upper part of a battery case according to an embodiment of the present invention, and the upper sealing part of FIG. 3 is vertical. An enlarged shape of the cross section A is shown in FIG. 4, and a planar shape in which only the electrode lead portion where the pattern is formed is enlarged is shown in FIG. 5. 6 illustrates a process in which the electrode lead film is attached to the electrode lead having the pattern of the inorganic particles formed on the surface thereof.

Referring to these drawings, a plurality of electrode tabs 140 protruding from the current collector (not shown) are integrally coupled and connected to the electrode lead 160. The electrode lead film 180 is positioned on the upper and lower surfaces of the electrode lead 160, respectively, and the electrode lead film 180 is positioned at an upper end portion of the battery case 120 while the ends opposing the electrode tabs 140 are exposed to the outside. Then, the battery case 120 is heat-sealed together with the electrode lead film 180. In this thermal fusion process, the electrode lead film 180 is integrated with the inner sealant layer 120c of the battery case 120.

Specifically, the battery case 120 is an outer seal layer 120a made of ONy (stretched nylon film), a barrier layer 120b made of aluminum, and an inner sealant layer 120c made of CPP (non-stretched polypropylene film). The inner sealant layer 120c is combined with the electrode lead film 180 in the heat fusion process.

On the other hand, the pattern 190 of the network structure made of inorganic particles is formed on the surface of the electrode lead 160 by the screen printing method, the pattern 190 has a predetermined thickness. Therefore, even when pressure (in some cases, heat and pressure) is unevenly applied during the thermal fusion process and the electrode lead film 180 and / or the inner sealant layer 120c are locally damaged, the pattern 190 may be a kind of support. It serves to prevent the electrode lead 160 from being completely exposed to the outside or contacting the electrode lead 160 with the metal barrier layer 120b.

Since the opening 190 has a plurality of openings 192 in the network pattern 190 to expose a substantial portion of the electrode lead 160, the pattern 190 is disposed between the electrode lead film 190 and the electrode lead 160. In spite of this, the electrode lead film 180 is partially melted in the heat fusion process to directly adhere to the electrode lead 160. Therefore, the problem of low adhesion when the inorganic material is added to the electrode lead film 190, that is, low melt bonding strength of the electrode lead film 190 to the electrode lead 160 can be solved.

Since the inorganic particles constituting the pattern 190 exhibit hydrophobicity by being treated with a silane compound, it is possible to prevent external moisture from flowing into the battery or leaking of the electrolyte inside the battery along the pattern 190. .

Although described with reference to the drawings according to an embodiment of the present invention, those skilled in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, in the secondary battery according to the present invention, the pattern of the inorganic particles is located between the electrode lead and the insulating film, so that the inner sealant layer of the insulating film and / or the battery case in the sealing process of the battery case by thermal fusion. It is possible to prevent the short circuit and the like generated while being damaged, and preferably to prevent the leakage of the electrolyte solution between the electrode lead and the insulating film by hydrophobic treatment, and ultimately the safety of the battery can be greatly improved.

Claims (13)

An electrode assembly having a cathode / separation membrane / cathode structure is embedded in a battery case of a laminate sheet including a resin layer and a metal layer, and an insulating film ('electrode lead film) interposed on an upper surface and a lower surface of an electrode lead connected to the electrode assembly. ') Is heat-sealed to the battery case during the manufacturing process of the battery, and the surface of the electrode lead or electrode lead film of the heat-sealed portion is composed of inorganic particles and a plurality of electrode lead and the electrode lead film can directly contact each other A secondary battery comprising a structure in which a predetermined pattern having openings is formed. The secondary battery of claim 1, wherein the laminate sheet is an aluminum laminate sheet. The secondary battery of claim 1, wherein the electrode lead film is made of non-stretched polypropylene. The secondary battery of claim 1, wherein the pattern is formed by applying inorganic particles onto an electrode lead or an electrode lead film before thermal fusion. The secondary battery of claim 4, wherein the pattern is formed by applying a printing paste including inorganic particles and a binder by a screen printing method. The secondary battery of claim 4, wherein the pattern has a network structure, a honeycomb structure, or a strip structure. The secondary battery of claim 1, wherein the thickness of the pattern has a size of 30 to 90% based on the thickness of the electrode lead film. The secondary battery of claim 1, wherein the opening has a size of 60 to 95% based on the total surface area of the pattern. The secondary battery of claim 1, wherein the inorganic particles are one or a mixture of two or more selected from the group consisting of alumina, silica, and titanium dioxide. The secondary battery of claim 1, wherein the surface of the pattern exhibits hydrophobicity. The secondary battery according to claim 10, wherein the inorganic particles are treated with a silane compound, and the pattern exhibits hydrophobicity. A medium-large battery pack comprising the secondary battery according to any one of claims 1 to 11 as a unit cell. The medium and large battery pack of claim 12, wherein the battery pack is used as a power source for an electric vehicle, a hybrid electric vehicle, or an electric bicycle.

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