KR102032514B1 - An electrode assembly with improved stability in use through a reinforcing structure by elastic polymer film at a local site within exterior materials and a lithium ion battery with the electrode assembly - Google Patents

Abstract

Secondary battery according to the present invention is an electrode assembly; And an exterior member having a structure in which an upper stamping portion and a lower stamping portion are repeatedly pressed to surround the outside of the electrode assembly, wherein the upper stamping portion and the lower stamping portion form a pleat pattern, and the electrode assembly includes a separator. At least one unit cell having a pair of electrode plates having different polarities; An electrode mixture applied on one or both surfaces of the pair of electrode plates; And electrode tabs protruding from the electrode plates at the same time, and wherein the electrode mixture is not coated, wherein the electrode tabs include tabs for parallel connection of electrodes and tabs for connecting electrode leads. One or more electrode tabs of the electrode parallel connection tab and the electrode lead connection tab are formed, and the elastic polymer film is reinforced on a localized portion of the packaging material.

Description

Electrode assembly with improved stability in use through a reinforcing structure by elastic polymer film at a local site within exterior materials and a lithium ion battery with the electrode assembly}

The present invention is an electrode constituting the battery in order to prevent the risk of ignition or explosion caused by breakage and internal short circuit, which is a mechanical problem of the battery which may be caused by external repetitive forces such as bending and twisting in a flexible environment The structure of reinforcing the elastomeric film on a local part in the enclosure facing the assembly prevents the cutting of the outermost electrode provided with the electrode lead connection tab and the parallel connection tab before the breakage or internal short circuit occurs. It is about the technology to ensure the safety of use by induction.

Secondary batteries (secondary battery) is a battery that can be charged and discharged, unlike a primary battery that can not be charged, and is widely used in the field of advanced electronic devices such as cellular phones, notebook computers, camcorders. As the weight reduction and high functionality of the portable electronic devices and the Internet of things (IoT) are developed, many researches on secondary batteries used as driving power sources have been made.

In particular, lithium secondary batteries have higher voltages and higher energy densities per unit weight than nickel-cadmium batteries or nickel-hydrogen batteries, which are widely used as power sources for portable electronic equipment.

The secondary battery is a battery using an electrochemical reaction generated between the electrolyte and the electrode when the positive electrode and the negative electrode are connected with the positive electrode and the negative electrode inserted into the electrolytic material. Unlike the conventional primary battery, the electric and electronic products Since the battery can be recharged and recharged by recharging the energy consumed by the charger, the trend is spreading with the popularization of wireless electric and electronic products.

In general, a lithium electrode-type wound electrode assembly in which a separator is inserted between a positive electrode plate and a negative electrode plate and spirally wound together, or a flexible stacked electrode assembly formed by stacking a plurality of positive electrode plates and a negative electrode plate with a separator interposed therebetween is lithium. I use it a lot in a secondary battery. For example, a cylindrical battery is one that houses a wound electrode assembly in a cylindrical can, injects electrolyte, and seals it, while a square cell compresses the wound electrode assembly or stacked electrode assembly to make it flat and flat, and then stores it in a square can. It is. In the pouch type battery, the wound electrode assembly or the stacked electrode assembly is packaged together with an electrolyte in a pouch type packaging material. In such an electrode assembly, the positive electrode tab and the negative electrode tab may be respectively drawn out of the electrode assembly from the positive electrode plate and the negative electrode plate and connected to the positive electrode and the negative electrode of the secondary battery.

On the other hand, the conventional pouch type lithium secondary battery is damaged by the intentional force applied to the exterior of the lithium secondary battery by the external force, the electrolyte leakage and the inflow of the outside air contained in the exterior material occurs. These electrolyte leaks interfere with normal operation such as corroding peripheral components such as battery protection circuits. In addition, it causes a large safety problem such as ignition due to the inflow of external air.

As a method for improving the durability of lithium secondary batteries, electrochemical driving is stably performed even when bending, torsion, etc., which is a force repeatedly applied by improving the durability of the battery by forming the exterior pattern and forming the terminal reinforcement structure of the lithium secondary battery. To make it possible.

On the other hand, in a flexible environment, a short circuit may occur due to breakage of the exterior material and misalignment or separation of internal electrodes due to repeated bending and torsion, such that a fire or explosion may occur. The internal short circuit generates excessive heat due to excessive current flow in proportion to the contact area between the anode and the cathode. In this case, an additional secondary short circuit may occur, which may cause a risk of fire and explosion.

In the general battery structure, in the case of the winding type or the general stacked battery, all the electrodes are connected to the outside, and an internal short circuit occurs when the electrode and the separator are damaged due to an external impact.

In the case where the internal short circuit occurs as described above, even if the internal electrode or the outermost electrode, which may be any part of the electrode assembly, may have a problem that only the capacity decreases, the current flows out of the electrode assembly. There is no problem with the operation, so there is no problem with the operation of the battery. However, when the continuous use in the broken and cut state of the internal electrode may be a problem to the safety there is a seriousness.

Referring to Korean Unexamined Patent Publication No. 10-2016-0090104, in order to overcome the problems of breakage and lack of electrolyte resistance when external force is applied from an external electrode assembly included in a conventional pouch type battery, a flexible battery electrode Disclosed is the provision of a reinforcing member on one surface of the assembly to prevent breakage even when an external force is applied.

(Patent Document 1) KR10-2016-0090104 A

Therefore, the problem to be solved by the present invention, through the structure of reinforcing the elastic polymer film on the local portion in the outer material in contact with the electrode assembly constituting the battery electrode lead connection before the breakage of the outer material or the internal short occurs An object of the present invention is to provide a structure that ensures safety in use by inducing cutting of the outermost electrode provided with a dragon tab.

Lithium ion secondary battery according to the present invention for achieving the above object is an electrode assembly; And an exterior member having a structure in which an upper stamping portion and a lower stamping portion are repeatedly pressed to surround the outside of the electrode assembly, wherein the upper stamping portion and the lower stamping portion form a pleat pattern, and the electrode assembly includes a separator. At least one unit cell having a pair of electrode plates having different polarities; An electrode mixture applied on one or both surfaces of the pair of electrode plates; And electrode tabs protruding from the electrode plates at the same time, and wherein the electrode mixture is not coated, wherein the electrode tabs include tabs for parallel connection of electrodes and tabs for connecting electrode leads. One or more electrode tabs of the electrode parallel connection tabs and the electrode lead connection tabs are formed, and the elastic polymer film is reinforced on a local portion between the electrode assemblies in contact with the packaging material.

The local part X reinforced with the elastic polymer film is 1/15 to 1/3 of the total length L of the packaging material.

Shore hardness of the elastic polymer film is 30 to 80 (shore A, A Type).

The elastomeric film is any one selected from the group consisting of unsaturated rubbers that can be cured by sulfur vulcanization, saturated rubbers cannot be cured by sulfur vulcanization, and thermoplastic elastomers. It includes the above.

The electrode assembly includes an outermost negative electrode plate disposed at the outermost side and an outermost positive electrode plate integrally disposed inside the outermost negative electrode plate, and the outermost negative electrode plate and the outermost positive electrode plate respectively have tabs and electrode leads for parallel connection of electrodes. Includes all tabs for the connection.

The electrode assembly may further include a reinforcement tab welded and fixed on the electrode lead connection tab of any of the electrode tabs constituting the electrode assembly.

The electrode assembly may be bent in an opposite direction by 180 ° while being bonded to the electrode lead connecting tab of any one of the electrode tabs constituting the electrode assembly to face the electrode assembly. It further includes a bending structure facing in the outward direction.

The tab lead coupling portion of the structure in which the electrode lead connection tab and the electrode lead are padded using the reinforcement tab is inserted into and aligned with the inside of the separator.

The tab-lead coupling portion to which the electrode lead connection tab and the electrode lead of the bent structure are coupled is inserted into and aligned inside the separator.

The outermost negative electrode plate disposed at the top and bottom of the electrode assembly is cross-coated with the electrode mixture.

According to the present invention, when tensile stress and compressive stress due to external bending are repeatedly applied on the electrode assembly, the outermost electrode portion facing the partial region of the exterior material in which the elastomeric reinforcement film is formed is repeatedly warped externally. Due to over bending, the stress is severely acted more severely than other parts, and is cut. As a result, the current is cut off, thereby losing the function of the battery and ensuring safety in use.

In addition, as the charge / discharge proceeds, the electrode expands and contracts in volume, and a portion of the electrode facing the region where the elastomeric reinforcement film is formed is continuously stressed due to repeated bending and bending outside. It is severely localized compared to other parts.

In the case where the outermost electrode provided with both the electrode lead connection tab and the parallel connection tab is cut, the process of losing the function of the battery by cutting off the current by cutting off the only passage through which electrons in the active material are connected to the outside To ensure the safety of use.

The outermost electrode and the general electrodes constituting the electrode assembly according to the present invention are connected by tabs for parallel connection, and the terminal is formed on the electrode lead connection tab portion on the outermost electrode, and external forces such as bending and twisting are applied from the outside. In case of loss, the outermost electrode is preferentially damaged and cut rather than the inner general electrodes. At this time, when the outermost electrode provided with the electrode lead connection tab is cut off, the general electrodes connected by the parallel connection tab are shut down in the state where the current is cut off, and the capacity decreases rapidly and the battery returns to its original state. It doesn't work.

1 shows an exemplary configuration of an electrode assembly constituting a flexible battery according to the present invention.
2 and 3 illustrate an exploded view of an electrode assembly in which the outermost electrode is disposed as a cathode in one embodiment.
4 illustrates a state in which an exterior material having a wrinkled pattern reinforced with an elastic polymer film surrounds an outer portion of an electrode assembly.
5 illustrates a state in which a general packaging material having a flat pattern reinforced with an elastic polymer film surrounds an outer portion of an electrode assembly.
FIG. 6 shows a state in which cutting occurs on the outermost cell so that the other internal electrodes constituting the electrode assembly are set to a closed state.
7 illustrates a flexible battery having an electrode assembly and an exterior member surrounding the electrode assembly.
FIG. 8 illustrates a pattern in which an upper stamping part and a lower stamping part are formed in a direction parallel to the width of the packaging part in the packaging material forming the flexible battery.
9 illustrates specific forms of the upper and lower stamp portions formed on the exterior member.
Figure 10 shows the bending evaluation results of the comparative examples different from the case where the elastic polymer film adopts a packaging material having a locally reinforced corrugated pattern according to the present invention.

Hereinafter, a flexible battery according to the present invention will be described with reference to the accompanying drawings.

The following examples are detailed description to help understand the present invention, and it should be understood that the present invention is not intended to limit the scope of the present invention. Therefore, equivalent inventions that perform the same functions as the present invention will also fall within the scope of the present invention.

In addition, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

1 to 3, an embodiment of an electrode assembly which improves stability in battery use by inducing cutting of an outermost electrode facing a portion of an outer material in which a locally elastic elastomeric reinforcement film is formed according to the present invention is described. Explain.

The electrode assembly is a unit cell (A) divided into the negative electrode plate 10 and the positive electrode plate 20 with the separator 30 interposed therebetween, an electrolyte that serves as an ion transfer medium between the negative electrode plate and the positive electrode plate, and protrudes from the electrode plate. The electrode tab is divided according to the parallel connection of the electrode and the electrode lead connection. At least one of the electrode plates including the negative electrode plate 10 and the positive electrode plate 20 may be spaced apart from the electrode parallel connection tab and the electrode lead connection tab on both sides. For example, any outermost negative electrode plate 10 disposed at the lowermost end of the electrode assembly 100 includes a tab 12 for negative electrode parallel connection and a tab 14 for negative electrode lead connection, and is directly connected to the outermost negative electrode plate 100. Any positive plate disposed on the top has a tab 22 for positive parallel connection and a tab 24 for positive lead connection. That is, the negative electrode and the positive electrode having both the tab for electrode parallel connection and the tab for electrode lead connection are integrally disposed at the lowermost end of the electrode assembly.

Herein, the electrode plates are applied to one or both surfaces of the electrode plate in which the electrode mixture is an electrode current collector, and the tabs for parallel connection of electrodes and the tabs for connecting electrode leads protrude from the electrode plates. Meanwhile, the electrode mixture is exposed in the uncoated state to the electrode parallel connection tab and the electrode lead connection tab.

The plurality of electrode plates are connected to the same pole through the electrode tab for parallel connection of the electrodes. That is, the plurality of negative electrode plates 10 and the plurality of positive electrode plates 20 are electrically connected in parallel by tab-tab coupling portions connecting the electrode tabs, respectively.

On the other hand, the electrode assembly has a structure that is electrically connected to the electrode lead exposed to the outside of the packaging material through the tab for connecting the electrode lead. The separator physically separates the electrode plates, but functions to pass ions included in the electrolyte.

The negative electrode plates disposed at the uppermost and lowermost ends of the electrode assembly may be in a state in which the negative electrode mixture 40 is applied only to a cross section.

The tabs 12 and 22 for parallel connection of electrodes in a state of protruding from the negative electrode plate 10 or the positive electrode plate 20 are electrically connected to each other by electrode plates having the same polarity. The parallel-connected tab-tab coupling is placed on a separator that surrounds the outer surface of the outermost electrode plate that forms the top or bottom of the electrode assembly and is finished tapered.

In the present invention, the connection between the tab-tab coupling portion in which the tabs 12 and 22 for parallel connection formed on the electrode plate are connected in parallel to each other and the tab-lead coupling portion in which the tabs 14 and 24 for connecting the electrode leads and the electrode lead are connected to each other And the joining is electrically connected through any one of the joining modes including joining by spot welding, ultrasonic welding, laser welding and conductive adhesive.

The electrodes disposed at the top and bottom of the electrode assembly are both negative electrode plates, but this is only an example and the present invention is not limited thereto. In the present invention, the uppermost and the lowermost electrodes may be disposed in the electrode assembly in any combination of a cathode / cathode, an anode / cathode, a cathode / anode, and an anode / anode.

The electrode assembly according to the present invention may reinforce a separate reinforcing tab on the electrode lead connection tabs 14 and 24 disposed on one side of the electrode assembly. By coupling the electrode leads to the reinforcing tabs, tab lead coupling portions having an overlay structure are formed using the reinforcing tabs of the electrode leads connecting tabs 14 and 24 and the electrode leads. The reinforcement bonding method for coupling the electrode leads tabs 14 and 24 and the electrode lead using the reinforcement tab corresponds to at least one of the positive electrode tab and the negative electrode.

The reinforcing tab is physically strengthened by reinforcing the strength of the connecting portions of the electrode leads connecting tabs 14 and 24 and the electrode leads. For example, the same or different metal reinforcing tabs thicker than 1 to 5 times thicker than the electrode lead connection tabs are welded on top of the electrode lead connection tabs extending from the electrode plate of the electrode assembly. Reinforcement tabs and tabs for connecting electrode leads that have been reinforced with padding have the same or different widths. The width of the reinforcing tab to be reinforced may be 3 mm to 5 mm, and the length may be 2 mm to 4 mm, but this is not limited thereto.

The electrode leads that engage with the tabs for connecting electrode leads by joining on reinforcement tabs reinforced with pads may specifically have a width of 2 mm to 3 mm and a length of 0.5 mm to 1 mm, but this is only one embodiment. It is not limited. In the present invention, the current collector of the electrode plate may be any one of a group containing aluminum, stainless steel and copper, the electrode lead may have a material of any one of the group containing aluminum, nickel and nickel coated copper. have. The tab for electrode lead connection and the reinforcing tab which reinforces on the tab lead connection part of the electrode lead are formed in the shape of one of the group containing a circle, an ellipse, and a polygon.

On the other hand, the electrode assembly according to the present invention may be in the form of coupling the electrode lead bending structure on the electrode lead connecting tabs (14, 24).

In a state where the electrode leads are arranged side by side on the upper side of the tab for electrode lead connection, a part of the end of the electrode lead is welded to the upper end of the tab for electrode lead connection. In the above state, the electrode lead is directed toward the outside of the electrode assembly from the electrode lead connection tab through the process of bending the electrode lead 180 degrees. This minimizes the local mechanical load in a flexible environment and is characterized by a joint reinforcement structure between the electrode tab and the electrode lead.

The bonding method through bending of the electrode lead connection tab and the electrode lead may correspond to at least one of a positive electrode tab and a negative electrode tab, and the width of the electrode lead coupled to the electrode lead connection tab is 2 mm to 3 mm, The length may be 1 mm to 3 mm, but this is merely an example and is not limited thereto.

The tab-lead coupling portion in which the electrode lead connection tabs 14 and 24 and the electrode lead are coupled using a reinforcing tab, or the tab-lead coupling portion in which the electrode lead connection tab and the electrode lead of the bending tab structure are coupled to the inside of the separator Has an inserted / arranged state. This protects by preventing external exposure of the terminal portion, which is the weakest point of the flexible battery.

4 is a view showing a state in which an exterior material having a corrugated pattern reinforced with an elastic polymer film surrounds the outside of the electrode assembly according to the present invention.

On the exterior member 200 surrounding the outside of the electrode assembly 100, an elastic polymer reinforcement film 240 having elastic properties may be disposed at any portion on the entire length L with respect to the longitudinal direction of the exterior member 200.

The elastic polymer reinforcement film 240 is disposed in a form that is thermally compressed on the valley portion of the packaging material 200 having a wrinkle pattern. The elastic polymer reinforcement film 240 may be thermally compressed or alternately disposed on all bone portions along the longitudinal direction of the exterior member 200.

The length X of the local part reinforced with the elastic polymer film is set to 1/15 to 1/3 of the total length L of the exterior material, and the width Y of the local part is preferably equal to the width of the electrode plate in the electrode assembly. The reason is that the cutting of the outermost electrode can be effectively induced by the binding force in the exterior material determined by the size of the elastic polymer film reinforcement portion and the bending applied from the outside.

The width Y of the elastic polymer film reinforcement part should not invade the sealing part of the exterior material, so that the battery stability such as electrolyte leakage and external air inflow due to damage of the sealing part during sealing of the exterior material should not be threatened.

When the length X of the elastomeric film reinforcing part is less than 1/15 of L, the cutting of the outermost electrode cannot be effectively induced, and the elastic film reinforcing work through thermocompression on the exterior material is not easy.

On the other hand, when the length of the exterior material L exceeds 1/3, the range is so wide that stresses caused by repeated bending and bending are dispersed, which also makes it difficult to induce effective cutting of the outermost electrode.

The elastic polymer reinforcement film 240 may be SEBS (Styrene-Ethylene-Butylene-Styrene, TPR).

The elastomeric reinforcing film is any one selected from the group consisting of vulcanized unsaturated rubbers (Unsaturated rubbers that can be cured by sulfur vulcanization), Saturated rubbers cannot be cured by sulfur vulcanization, and Thermoplastic elastomers It includes the above.

For vulcanized unsaturated rubbers, natural polyisoprene (cis-1,4-polyisoprene (Natural rubber), trans-1,4-polyisoprene (Gutta-percha)), Polyisoprene rubber (IR), Polybutadiene rubber (BR), Polychloropene rubber ( CR), Neoprene, Bayprene etc., Poly (isobutyleneco-isoprene) rubber (IIR), Chloro IIR (CIIR), Bromo IIR (BIIR), Poly (styreneco-butadiene) rubber (SBR), Poly (acrylonitrile-co-butadiene ) rubber (NBR), hydrogenated NBR (HNBR), Therban, Zetpol, etc.

In the case of unsaturated saturated rubber, Epichlorohydrin rubber (ECO), Polyacrylic rubber (ACM, ABR), Silicone rubber (SI, Q, VMQ), Fluorosilicone rubber (FVMQ), Polyether block amides (PEBA), Chlorosulfonated polyethylene (CSM), Hypalon, Ethylene-vinyl acetate (EVA) and the like.

In the case of thermoplastic elastomers, there are thermoplastic styrenic block copolymers (TPE-s), for example, polystyrene-blockpolybutadiene-block-polystyrene (SBS), polystyrene-block-polyisoprene-blockpolystyrene (SIS), Polystyrene-block-poly (ethylene-ran-propylene) -blockpolystyrene (SEPS), polystyrene-block-poly (ethylene-ran-butylene) -blockpolystyrene (SEBS), and the like.

Another thermoplastic elastomer, an olefin polymer blend, is called Thermoplastic polyolefin blends (TPE-o). These polymers are elastomeric alloys incorporating the above-mentioned TPE-s such as SBS, SIS, SEPS, SEBS, and polyolefins such as PS, PP, and PE. Other thermoplastic elastomers include Thermoplastic polyurethanes (TPU), Thermoplastic copolyesters and Thermoplastic polyamides.

Finally, thermoplastic vulcanizate elastomers (TPV) include ethylene propylene monomer (EPM) rubber, ethylene propylene dienemonomer (EPDM) rubber, fluroelastomer (FKM, and FEPM), and Perfluoroelastomers (FFKM).

In addition, the Shore hardness of the elastic polymer reinforcement film 240 is 30 to 80 (Shore A, A Type). Hardness is the amount of resistance to deformation of an object when it is pressed against another object. It is divided into Vickers hardness, Brinell hardness, Rockwell hardness, Shore hardness and the like, in the case of the elastic polymer is measured and described as Shore hardness. Shore hardness tester is a measure of the amount of jumping after pressing an object with various types of indenters (needle shape). The types are classified into A, B, C, D, OO, etc. according to the shape of the indenter. The elastic polymer reinforcement film 240 is preferably A to 30 to 80, for that reason it is difficult to effectively cut the outermost electrode in the electrode assembly due to the low hardness at less than 30, in the operation such as bending or twisting beyond 80 It is difficult to exert the normal performance of the flexible battery by damaging the exterior material and the electrode assembly.

FIG. 5 is a comparative example of an embodiment according to the present invention, in which a general packaging material having a flat pattern reinforced with an elastic polymer film surrounds an outer portion of an electrode assembly.

Figure 6 shows a state in which the other internal electrodes constituting the electrode assembly is set to a closed state (shut down) by cutting occurs on the outermost battery according to the present invention.

Specifically, a plurality of batteries constituting the electrode assembly is connected through a tab for parallel connection on the right side, and a terminal is formed in the tab portion for electrode lead connection in the electrode plate disposed at the outermost part of the lower end of the plurality of batteries.

In this state, when external forces such as bending and torsion are applied on the electrode assembly from the outside, the electrode at the outermost portion of the lower end portion is preferentially damaged and cut rather than inside the electrode assembly.

At this time, when the outermost electrode provided with the electrode lead connection tab is cut off, the electrodes connected by the parallel connection tab are cut off, the current is closed, and the capacity decreases rapidly, thereby preventing the battery from functioning. . This provides a function that prevents, in spite of the damage of the internal electrode, differently from the existing battery which has a risk of ignition that can occur due to the internal short-circuit in continuous use.

To this end, the present invention appropriately utilizes the type and arrangement of the outermost electrode to induce the cutting of the electrode provided with a tab for electrode lead connection before the breakage of the exterior material or the internal short circuit occurs. This intended structure can be applied to devices that safeguard the battery from the risks of inadvertent or excessive bending by the user and require performance assurance and control of the flexible battery over a certain number of bending times by external forces.

Referring to FIG. 7, the electrode assembly according to the present invention arranges the exterior member 200 having a structure in which the upper stamping portion and the lower stamping portion are repeatedly pressed to surround the outside of the electrode assembly.

Referring to FIG. 8, the plurality of upper and lower indents repeatedly pressed on the exterior member are repeatedly patterned and shaped to enable compression and tension of the flexible battery having the electrode assembly in bending, torsion, or fold. .

The plurality of upper stamp parts and lower stamp parts are continuously formed in a direction parallel to the widths of the electrode assembly and the exterior member.

The plurality of upper stamping portions and lower stamping portions are pressed into upper and lower molds, respectively.

The exterior part surrounding the outside of the electrode assembly may have a shape having an upper exterior part 210 and a lower exterior part 220 on the electrode assembly based on the red dotted line of the sealing part 230. That is, the plurality of upper stamping parts 212 and 222 and the lower stamping parts 214 and 224 repeated on the outer cover part are formed in a symmetrical structure with respect to the sealing part, and the upper outer cover part 210 and the lower outer cover part ( 220 is symmetrically stamped on. In this state, the sealing unit is bent up and down symmetrically to accommodate the electrode assembly inside the exterior member.

The width of the sealing portion, which is a reference for distinguishing the upper and outer sheaths 210 and 220, may be 3 mm to 5 mm, and the actual sealing width may be 1 mm to 2 mm, but this is only one embodiment. It is not limited.

Referring to FIG. 9, the plurality of upper stamping unit heights h and the lower stamping unit heights h 'repeated on the exterior member may be the same (h = h').

The plurality of upper indenter height h and the lower indenter height h 'repeated on the exterior member are 0.5 mm to 1 mm and an optimum value of 0.75 mm, but this is merely an example and the present invention is not limited thereto.

Although the thickness of the elastic polymer film that is thermally compressed by the upper press portion height h and the lower press portion height h 'formed on the exterior member is determined to be 0.5 mm to 1 mm, this is only an example and is limited thereto. It is not.

When the thickness of the elastomeric film is less than 0.5 mm, it is not possible to effectively induce the cutting of the outermost electrode. When the thickness exceeds 1 mm, high pressure is applied to the electrode assembly and the exterior material by the elastomeric film reinforcement part. In addition to the damage and breakage such as wrinkles of the exterior material, the outermost electrode is cut and a momentary overvoltage occurs, which makes the flexible and normal electrochemical driving difficult.

On the other hand, the width (a) between the top of the plurality of upper push-in portion and the bottom of the bottom of the lower push-in portion is the same (a = b) to form a wave pattern.

The present invention arranges the negative electrode of the outermost electrode of the electrode assembly having a plurality of electrodes stacked up and down through the separator to prevent breakage of the electrode terminal during bending of the flexible battery.

Figure 10 shows the bending evaluation results of the comparative examples different from the case where the elastic polymer film adopts a packaging material having a locally reinforced corrugated pattern according to the present invention.

In FIG. 10, the top graph shows an embodiment according to the present invention, but after the bending evaluation, there is no damage to the wrinkles and sealing parts of the exterior material, but the outermost electrode can be confirmed that the cut is performed at about 2,000 bending times.

Specifically, as an embodiment according to the present invention, when the battery is provided with the elastomeric reinforcement film locally in the wrinkled patterned exterior member, cutting of the outermost electrode occurs around 2,000 times, whereby the capacity decreases rapidly and the voltage is reduced. It falls below the operating voltage and shows much better bending durability than that of Comparative Example 1, which is the lowest graph.

It can be seen that since the force is continuously concentrated on the outermost electrode facing the locally formed elastomeric reinforcing film facing the corrugated pattern having the corrugation pattern, it causes the mixture layer crack of the outermost electrode and cutting of the current collector.

The lowermost graph in FIG. 10 shows Comparative Example 1 in which a general packaging material having a flat pattern reinforced with an elastic polymer film surrounds the outer periphery of the electrode assembly, as shown in FIG. 5.

In Comparative Example 1, both the damage of the exterior material and the cutting of the outermost electrode are made.

In the case of Comparative Example 1, when the bending evaluation of 25 cpm (25 times / 1 minute) is carried out, the damage to the outer material and the outermost electrode is cut in less than 100 times, it can be seen that the voltage suddenly surges and bounces.

This means that the input current is constant but the outermost electrode is cut, so that the common electrodes connected by the parallel connection taps are shut down while the current is cut off, and the capacity is drastically reduced. It is caused by sudden overvoltage as it grows. In the case of a general battery, all the electrodes are bundled together and connected to the outside. However, the present invention has a single electrode having a movement passage of electric current flowing to the outside of the battery, that is, a tab for electrode lead connection. Disconnection of the battery occurs.

The center graph in FIG. 10 shows the comparative example 2, and it can be seen that there is no damage to the exterior material and the cutting of the outermost electrode does not occur. On the other hand, at 8,000 bending times or more, both the electrode and the packaging material are damaged.

Comparative Example 2, which is a general flexible battery, has a high probability of occurrence of an internal short circuit due to breakage of the exterior material or lithium deposition at about 8,000 repeated bending times.

The present invention intentionally induces the outermost electrode to be cut first 8,000 times or less by introducing an exterior member having a flat pattern reinforced with an elastic polymer film before the above short circuiting occurs.

As a result of many experiments as described above, by forming an elastomeric reinforcement film locally in the corrugated packaging having a corrugated pattern, the electrode is cut off and the battery is disconnected at a localized region at about 1,500 to 2,500 bending times, thereby causing damage to the packaging. Intentionally designing damage and cutting of the outermost electrode prior to excessive bending times with a high probability of occurrence of internal short circuits due to lithium precipitation ensures battery safety.

According to the present invention, when the tensile stress and the compressive stress due to external bending on the electrode assembly are repeatedly applied, the outermost electrode part facing the partial region of the exterior material in which the elastomeric reinforcement film is formed is repeatedly bent and bent from the outside. Due to this structure, the stress acts more severely than the other parts, and the current is cut off by cutting so that the battery function can be lost from the risks of user's carelessness or excessive bending and the safety of use can be secured. .

Claims (13)

An electrode assembly; And
And an exterior material surrounding the outside of the electrode assembly and having a repeating upper and lower stamp parts.
The electrode assembly,
At least one unit cell having a pair of electrode plates having different polarities with a separator therebetween;
An electrode mixture applied on one or both surfaces of the pair of electrode plates; And
Electrode tabs protruding from the electrode plates, respectively;
The electrode tab,
Tabs for parallel connection of electrodes connecting the electrode plates to one another; And
An electrode lead connection tab coupled to an electrode lead exposed to the outside of the exterior material;
So that the electrode assembly is closed by damage to the electrode plate disposed on the outermost of the electrode assembly,
The electrode lead connection tab is formed on an electrode plate disposed on the outermost side of the electrode assembly,
A secondary battery, characterized in that the elastic polymer film is formed to cover a portion of the upper stamping portion or the lower stamping portion and to face a portion of the electrode plate disposed on the outermost portion of the electrode assembly.
The method of claim 1,
The secondary battery of claim 1, wherein the length X of the portion where the elastic polymer film is bonded is in the range of 1/15 to 1/3 of the total length L of the packaging material in the direction of repeating the upper and lower stamp parts.
The method of claim 1,
Shore hardness of the elastic polymer film (Shore hardness) is a secondary battery, characterized in that 30 to 80 (Shore A, A Type).
The method of claim 1,
The elastomeric film is any one selected from the group consisting of unsaturated rubbers that can be cured by sulfur vulcanization, saturated rubbers cannot be cured by sulfur vulcanization, and thermoplastic elastomers. Secondary battery containing the above.
The method of claim 1,
The electrode assembly includes an outermost anode plate disposed at an outermost side and an outermost anode plate disposed to face the outermost cathode plate, with the separator interposed therebetween.
Secondary batteries are formed in the outermost negative electrode plate and the outermost positive electrode plate both tabs for the parallel connection of electrodes and tabs for connecting the electrode leads.
The method of claim 1,
The electrode assembly,
And a reinforcing tab coupled to the electrode lead connection tab.
The method of claim 1,
The electrode lead is,
On the electrode lead connection tab, the secondary battery further comprises a bending structure formed to be bent in a direction toward the outside of the electrode assembly from the side facing the electrode assembly.
The method of claim 6,
The tab lead coupling portion padded by the reinforcing tab is inserted into the separator.
The method of claim 7, wherein
And a tab-lead coupling part to which the tab for electrode lead connection and the electrode lead having a bent structure are coupled are inserted into the separator.
The method of claim 1,
The outermost negative electrode plates disposed on the top and bottom of the electrode assembly is a secondary battery, the electrode mixture is coated on one side.
The method of claim 1,
The secondary battery, characterized in that the width Y of the elastic polymer film is smaller than the width between the sealing portions formed at both ends of the packaging material in the direction in which the upper stamping portion and the lower stamping portion extends.
The method of claim 1,
The secondary battery according to claim 1, wherein the width Y of the elastic polymer film is equal to the width of the electrode plate in a direction in which the upper stamping part and the lower stamping part extend.
The method of claim 1,
The elastic polymer film is a secondary battery, characterized in that the thermocompression bonding to the bone portion formed by the upper and lower indentation.

Images