KR101984265B1 - Pouch type secondary battery and method of fabricating the same - Google Patents

Abstract

The present invention relates to an electrode assembly comprising a positive electrode plate, a separator and a negative electrode plate for improving the sealing of the electrode lead portion and improving safety; At least two positive electrode tabs and negative electrode tabs protruding from the positive electrode plate and the negative electrode plate of the electrode assembly; A cathode lead and a cathode lead electrically connected to the at least two positive electrode taps and the negative electrode tab, respectively; And a pouch-shaped case accommodating the electrode assembly such that a part of the positive electrode lead and the negative electrode lead are exposed to the outside by a heat fusion line formed in a peripheral portion, wherein the positive electrode lead and the negative electrode lead, Wherein a pair of lead films each comprising an upper surface lead film and a lower surface lead film are adhered to each other so that stepped ends are formed on both end portions of the lead films.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pouch type secondary battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pouch-type secondary battery and a method of manufacturing the same. More particularly, the present invention relates to a pouch-type secondary battery improved in sealing area and a method of manufacturing the same.

2. Description of the Related Art Generally, a secondary battery refers to a battery that can be charged and discharged unlike a primary battery that can not be charged, and is widely used in electronic devices such as mobile phones, notebook computers, camcorders, and electric vehicles (EVs). Particularly, the lithium secondary battery has an operating voltage of about 3.6 V and has a larger capacity than a nickel-cadmium battery or a nickel-hydrogen battery, which is widely used as a power source for electronic equipment, and has a high energy density per unit weight. As shown in Fig.

The lithium secondary battery mainly uses a lithium-based oxide and a carbonaceous material as a cathode active material and an anode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate each coated with such a positive electrode active material and a negative electrode active material are disposed with a separator interposed therebetween, and an outer cover material, that is, a battery case, for sealingly storing the electrode assembly together with the electrolyte solution. The lithium secondary battery can be classified into a can-type secondary battery in which an electrode assembly is embedded in a metal can, and a pouch-type secondary battery in which an electrode assembly is embedded in a pouch of an aluminum laminate sheet, depending on the shape of the battery case.

The pouch type secondary battery is divided into a unidirectional battery in which an electrode lead connected to a positive / negative tab of a secondary battery is directed to one side, or a bidirectional battery which faces in a facing direction. A lead film is formed on both sides of the electrode lead to secure insulation characteristics.

However, among the sealed regions of the pouch, the portions where the lead films are formed are relatively poor in sealing, so that gas, electrolytic solution, or the like may leak due to overcharging or internal short-circuiting of the cells.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a pouch type secondary battery with improved safety by improving sealing of an electrode lead portion of a pouch type secondary battery and a method of manufacturing the same.

According to an aspect of the present invention, there is provided a secondary battery including: an electrode assembly including a positive electrode plate, a separator, and a negative electrode plate; At least two positive electrode tabs and negative electrode tabs protruding from the positive electrode plate and the negative electrode plate of the electrode assembly; A cathode lead and a cathode lead electrically connected to the at least two positive electrode taps and the negative electrode tab, respectively; And a pouch-shaped case accommodating the electrode assembly such that a part of the positive electrode lead and the negative electrode lead are exposed to the outside by a heat fusion line formed in a peripheral portion, wherein the positive electrode lead and the negative electrode lead, And a pair of lead films each of which is composed of an upper surface lead film and a lower surface lead film are adhered to each other so that stepped ends are formed on both end portions of the pair of lead films.

Preferably, the widths of the upper surface lead film and the lower surface lead film are the same and the centers of the widths of the lead films are shifted.

Preferably, the stepped portion may have a length of 0.01 to 5% of the width of the electrode lead.

Preferably, the lead film may have a thickness of 0.1 to 2 mm.

Preferably, the lead film may be an insulating film.

Preferably, the lead film is made of polyimide (PI), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET) and polyvinyl chloride (PVC) (Mono-layer or multi-layer).

Preferably, the pouch-shaped case may be in the form of an aluminum pouch in which an aluminum foil is interposed between an insulating layer made of a polymer and an adhesive layer.

According to an aspect of the present invention, there is also provided a method of manufacturing an electrode assembly, including the steps of: providing an electrode assembly to which positive and negative electrode leads are connected; Attaching a pair of lead films to the electrode leads so as to form steps; And a step of sealing the upper and lower sheets of the battery case by attaching the electrode assembly to the inside of the pouch-shaped battery case and along the outer periphery of the battery case so that the electrode lead protrudes to the outside, A method of manufacturing a battery is provided.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to improve the durability of the secondary battery against overcharging / internal short-circuiting by improving the sealing property of the electrode lead portion.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further the understanding of the technical idea of the invention, And should not be construed as limiting.
1 and 2 are sectional views of an electrode lead portion of a conventional pouch type secondary battery.
3 is a cross-sectional view of an electrode lead portion of a pouch type secondary battery according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

The pouch type secondary battery according to the present invention comprises an electrode assembly including a positive electrode plate, a separator, and a negative electrode plate; At least two positive electrode tabs and negative electrode tabs protruding from the positive electrode plate and the negative electrode plate of the electrode assembly; A cathode lead and a cathode lead electrically connected to the at least two positive electrode taps and the negative electrode tab, respectively; And a pouch-shaped case for accommodating the electrode assembly such that a part of the positive electrode lead and the negative electrode lead are exposed to the outside by a heat fusion line formed in a peripheral portion, wherein the positive electrode lead and the negative electrode lead are respectively connected to the upper surface lead film A pair of lead films made of a lead film are adhered to each other so that stepped ends are formed on both end portions of the pair of lead films.

The electrode assembly is configured such that at least one positive electrode plate and at least one negative electrode plate are disposed with a separator interposed therebetween, and is housed in a pouch-shaped case. At this time, the electrode assembly may be housed in a pouch-shaped case in a state where a plurality of positive plates and negative plates are laminated, or may be housed in a pouch-shaped case with one positive plate and a negative plate wound.

The electrode plates of the electrode assembly are formed of a structure in which an active material slurry is applied to a current collector made of aluminum (Al) or copper (Cu). The slurry is usually prepared by adding a solvent to granular active materials, auxiliary conductors, binders and plasticizers And then agitated. Each of the electrode plates may have an uncoated portion to which no slurry is applied, and an electrode tab corresponding to each electrode plate may be formed on the uncoated portion.

The cathode active material may be a chalcogenide compound so that lithium ions can intercalate / deintercalate. For example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _{1 - x} Co _x O ₂ (0 < x < 1), LiMnO _2, or the like. The negative electrode active material may be a carbonaceous material, silicon (Si), tin (Sn), tin oxide, tin alloy composite, transition metal oxide, lithium metal nitride Or a lithium metal oxide or the like.

The separation membrane is interposed between the positive and negative electrode plates to prevent a short circuit between the positive and negative electrode plates, and only the lithium ion can move due to the separation membrane. The separator may be formed of polyolefin. Specific examples of the polyolefin include polyethylene such as high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra high molecular weight polyethylene (UHMWPE) and the like; Polypropylene; Polybutylene; Polypentene: polyhexene: polyoctene: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, and octene, or a mixture thereof, but is not limited thereto.

The electrode tab is composed of, for example, a positive electrode tab and a negative electrode tab, and is formed to protrude from the electrode assembly. That is, the positive electrode tab is formed so as to protrude from the positive electrode plate of the electrode assembly, and the negative electrode tab is formed to protrude from the negative electrode plate of the electrode assembly. At this time, the positive electrode tab or the negative electrode tab may protrude in a form attached to the positive electrode plate or the negative electrode plate, and may be made of the same material as the positive electrode collector or the negative electrode collector, respectively.

The plurality of electrode tabs may be provided in one electrode assembly. For example, a plurality of positive electrode tabs may be provided on the positive electrode plate, and a plurality of negative electrode tabs may be provided on the negative electrode plate. In this case, a plurality of positive electrode tabs may be connected to one positive electrode lead, and a plurality of negative electrode tabs may be connected to one negative electrode lead. Also, one positive electrode tab and one negative electrode tab may be provided in one electrode assembly.

The positive electrode tab and the negative electrode tab may protrude in opposite directions with respect to the electrode assembly. The electrode lead is a thin plate-shaped metal, one end of which is attached to the electrode tab, and the other end, that is, the opposite end is exposed to the outside of the pouch-shaped case. The electrode lead may be attached to the upper or lower portion of the electrode tab. The positive electrode lead and the negative electrode lead may have different materials from each other. That is, the positive electrode lead may be made of aluminum material, for example, like the positive electrode plate, and the negative electrode lead may be made of a copper material or a copper material coated with nickel (Ni), for example.

The lead film is made of a film having insulation and heat-sealability. The lead film may be formed of, for example, polyimide (PI), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (A single film or a multi-layer film). The lead film prevents a short circuit between the electrode lead and the metal layer of the pouch-shaped case, for example, between the aluminum sheet, and also improves the sealing force of the pouch-type case to prevent electrolyte leakage.

FIGS. 1 and 2 are cross-sectional views of an electrode lead portion of a conventional pouch type secondary battery, and FIG. 3 is a sectional view of an electrode lead portion of a pouch type secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, a pair of lead films 300 are attached to an electrode lead 200 of a conventional pouch-type secondary battery, and surrounding portions of the pouch-type case 100 are thermally fused and sealed. Referring to FIG. 2, a space where the pouch-type case 100 is not sealed due to the lead film having a certain thickness is generated. When the secondary battery expands due to overcharging or internal short-circuit, gas or electrolyte may leak have.

Referring to FIG. 3, the pouch type secondary battery according to the present invention has a pair of lead films 300 attached thereto with a step (A), thereby reducing a portion that is not sealed as compared with a conventional pouch type secondary battery, The durability of the secondary battery with respect to overcharging / internal short circuit and the like can be improved.

The step difference may be formed by varying the widths of the upper surface lead film and the lower surface lead film and may be formed by attaching the upper surface lead film having the same width and the lower surface lead film so that the centers of the widths of the lead films are shifted .

The step may have a width of 0.01 to 5% of the width of the electrode lead. If the stepped portion is smaller than 0.01% or greater than 5% of the width of the electrode lead, there is a problem that the area where the pouch-shaped case is not sealed increases.

In this embodiment, the pouch-shaped case may be configured in the form of an aluminum pouch in which an aluminum foil is interposed between an insulating layer made of a polymer and an adhesive layer. The insulating layer made of a polymer can serve as a substrate and a protective layer, and can primarily protect the electrode assembly housed therein from an external impact or the like. The insulating layer made of a polymer may be formed of a resin material such as nylon or polyethylene terephthalate (PET), but is not limited thereto. The aluminum thin film can serve as a substrate for maintaining the mechanical strength and a barrier layer for preventing penetration of moisture and oxygen. The adhesive layer is also referred to as a heat-sealable layer, and has a thermal adhesive property and can serve as a sealing agent. The adhesive layer may be formed of a polyolefin resin material. Commonly used as a polyolefin-based resin layer is CPP (Casted Polypropylene). The adhesive layer may be formed of a material selected from the group consisting of a polyolefin resin such as chlorinated polypropylene, polyethylene, an ethylene propylene copolymer, a polyethylene and an acrylic acid copolymer, and a copolymer of polypropylene and acrylic acid. However, But is not limited thereto. The total thickness of the pouch-shaped case is usually 40 to 120 占 퐉, and the insulating layer, the adhesive layer and the aluminum thin film are preferably 10 to 40 占 퐉 and 20 to 100 占 퐉, respectively, but are not limited thereto.

The pouch-type case may be composed of an upper sheet and a lower sheet. The space in which the electrode assembly can be housed can be formed in either the upper sheet or the lower sheet, or both the upper sheet and the lower sheet. On the other hand, when the electrode assembly is housed in the accommodating space of the upper sheet or the lower sheet, the upper sheet and the lower sheet are bonded together by thermal fusion or the like and sealed.

The pouch type secondary battery according to the present invention may be a component of a battery pack including a plurality of pouch type secondary batteries.

The battery pack according to the present invention may be a component of a battery driving system including a battery pack and a load supplied from the battery pack.

Examples of the battery driving system include an electric vehicle (EV), a hybrid vehicle (HEV), an electric bicycle (E-Bike), a power tool, an energy storage system, an uninterruptible power supply (UPS) A battery pack, a portable computer, a portable telephone, a portable audio device, a portable video device, and the like. An example of the load is a power supplied from a motor or a battery pack, And may be a power conversion circuit for converting the power into a required power.

According to another aspect of the present invention, there is provided a method of manufacturing a pouch type secondary battery, the method comprising: providing an electrode assembly including positive and negative electrode leads; Attaching a pair of lead films to the electrode leads so as to form steps; And attaching the electrode assembly to the inside of the pouch-shaped battery case and bonding the upper and lower sheets of the battery case along the outer periphery of the battery case so that the electrode lead protrudes to the outside.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the details thereof and that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. And various modifications and variations are possible within the scope of the appended claims.

100: Pouch type case
200: electrode lead
300: lead film

Claims (8)

An electrode assembly including a positive electrode plate, a separator, and a negative electrode plate; At least two positive electrode tabs and negative electrode tabs protruding from the positive electrode plate and the negative electrode plate of the electrode assembly; A cathode lead and a cathode lead electrically connected to the at least two positive electrode taps and the negative electrode tab, respectively; And a pouch-shaped case accommodating the electrode assembly such that a part of the positive electrode lead and the negative electrode lead are exposed to the outside by a heat fusion line formed at a peripheral portion,
Wherein the positive electrode lead and the negative electrode lead are attached to a pair of lead films each comprising an upper surface lead film and a lower surface lead film,
The lead film may be formed of any one selected from the group consisting of polyimide (PI), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and polyvinyl chloride Wherein the pouch type secondary battery comprises a layer of the above material. The method according to claim 1,
Wherein the upper surface lead film and the lower surface lead film have the same width and are joined so that the centers of the widths of the lead films are shifted. The method according to claim 1,
Wherein the step has a length of 0.01 to 5% of the width of each of the positive electrode lead and the negative electrode lead. The method according to claim 1,
Wherein the lead film has a thickness of 0.1 to 2 mm. The method according to claim 1,
Wherein the lead film is an insulating film. delete The method according to claim 1,
Wherein the pouch-shaped case is in the form of an aluminum pouch in which an aluminum foil is interposed between an insulating layer made of a polymer and an adhesive layer. Providing an electrode assembly in which electrode leads of an anode and a cathode are connected;
Attaching a pair of lead films to the electrode leads so as to form steps; And
And attaching the electrode assembly to the inside of the pouch-shaped battery case and sealing the upper and lower sheets of the battery case along the outer periphery of the battery case so that the electrode lead protrudes to the outside. A method of manufacturing a pouch-type secondary battery according to claim 1.

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