KR20170013063A - Pouch type secondary battery and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a pouch type secondary battery comprising an electrode assembly and a pouch case receiving the electrode assembly. The pouch type secondary battery comprises: a lower case having an internal space to receive the electrode assembly; an upper case covering the internal space by combining to the lower case; a sealing part formed at a part combining the upper case and the lower case; and a welding part which seals the sealing part by connecting the side of the upper case and the side of the lower case.

Description

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

The present invention relates to a pouch type secondary battery and a method of manufacturing the same, and more particularly, to a pouch type secondary battery having an improved sealing structure of a pouch case and a method of manufacturing the same.

Generally, a secondary battery refers to a battery that can be charged and discharged unlike a primary battery which 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. .

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 a positive electrode active material and a negative electrode active material are disposed with a separator interposed therebetween, and a battery case, which encloses 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.

Generally, when manufacturing a pouch-type secondary battery, the pouch case is sealed using high-temperature heat in order to prevent moisture or outside air from entering the battery.

The sealing of the pouch case proceeds by fusing a polymer such as polypropylene on the inner surface of the pouch to heat. The water in the air slowly permeates through the polymer layer, and the performance of the cell is deteriorated. A pouch case having a sealing surface of a certain width or more is considered, but there is a problem that there are many restrictions on the use of the side space, so that a technology development is required.

SUMMARY OF THE INVENTION The present invention provides a pouch-type secondary battery that can prevent moisture penetration by welding a side surface of a pouch case with a metal, and a method of manufacturing the same.

Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

According to an aspect of the present invention, there is provided a pouch type secondary battery including an electrode assembly and a pouch case for accommodating the electrode assembly, wherein the pouch case includes a lower portion having an internal space for accommodating the electrode assembly, The upper case and the lower case are connected to each other by a sealing part formed at a portion where the upper case and the lower case are joined to each other, A pouch type secondary battery comprising:

The upper case and the lower case may have a structure in which a metal layer-insulating layer is laminated, or a structure in which a heat-welding layer-metal layer-insulating layer is sequentially laminated.

The welded portion may be welded to seal the sealing portion by connecting the metal layers exposed on at least one side of the upper case and the lower case to each other.

The welded portion may be formed by melting at least one metal selected from the group consisting of stainless steel, aluminum, copper, lead, zinc, magnesium, tin, chromium, brass alloy, phosphor bronze, silicon manganese copper and bronze.

Wherein the heat-sealable layer is a single film made of any one material selected from the group consisting of a polyolefin, a polycarbonate, a polyvinyl chloride, an acrylic polymer, a polyamide, a cellulose, a polyester, a polybenzoxazole, a fluororesin, And may have a composite membrane structure composed of two or more material layers.

The insulating layer may have a single film composed of any one material selected from the group consisting of polyester, polycarbonate and polyamide, or a composite film structure composed of two or more material layers.

The metal layer may have a metal thin film structure composed of any one of iron, carbon, chromium and manganese alloy, iron, chromium and nickel alloy or aluminum.

The present invention has an advantage in that water can be prevented from penetrating into the battery by sealing the sealing portion by welding the side surface of the pouch case.

Further, since the area of the sealing portion is reduced, there is an advantage that the space utilization rate of the pouch type secondary battery is improved.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and, together with the description of the invention, It is not interpreted.
1 is a perspective view schematically showing a pouch case.
2 is a cross-sectional view of a pouch type secondary battery according to an embodiment of the present invention.
3 is an enlarged view of a sealing part and a weld part included in the pouch type secondary battery according to an embodiment of the present invention.
4 is an enlarged view of a sealing part and a weld part included in the pouch type secondary battery according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms or words used in the specification and claims should not be construed in a conventional or dictionary sense, and the inventor should properly define the concept of the term to describe its invention in the best possible way. It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, at the time of the present application, It should be understood that various equivalents and modifications may be made.

A pouch-type secondary battery according to an embodiment of the present invention includes an electrode assembly and a pouch case accommodating the electrode assembly.

The electrode assembly is not shown in the drawings for the sake of convenience, but is configured in such a manner 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 the pouch case. At this time, the electrode assembly may be housed in the pouch case in a state where a plurality of positive and negative electrode plates are stacked, or may be housed in the pouch case in a state where one positive electrode plate and the negative electrode plate are 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 the like. 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.

For example, LiMnO ₂ Li _x CoO ₂ (0.5 < x < 1.3), Li _x NiO ₂ ( 0.5 <x <1.3), Li _x MnO ₂ (0.5 <x <1.3), Li _x Mn ₂ O ₄ (0.5 <x <1.3), Li _x (Ni _a Co _b Mn _c ) O ₂ 1.3, 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), Li _x Ni _{1 -y} Co _y O ₂ 1), Li _x Co _{1 - y} Mn _y O ₂ (0.5 <x <1.3, 0? Y <1), Li _x Ni _{1 -y} Mn _y O _{2 1), Lix (Ni a Co} b Mn c) O4 (0.5 <x <1.3, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li x Mn _{2 - z Ni z O 4 (} 0.5 <x <1.3, 0 <z <2), Li x Mn 2 - z Co z O 4 (0.5 <x <1.3, 0 <z <2), Li x CoPO 4 ( 0.5 <x <1.3) and Li _x FePO ₄ (0.5 <x <1.3), or a mixture of two or more thereof. 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 electrode plate and the negative electrode plate to prevent a short-circuit that may occur between the positive electrode plate and the negative electrode plate, and only the lithium ion can be moved due to the separation membrane. A porous polymer base material and a porous coating layer formed on at least one side of the porous polymer base material.

The porous polymer base may be a porous polymer film base or a porous nonwoven base.

The porous polymeric film substrate may be a porous polymeric film made of a polyolefin such as polyethylene or polypropylene. The polyolefin porous polymeric film substrate exhibits a shutdown function at a temperature of, for example, 80 to 130 ° C.

At this time, the polyolefin porous polymer film may be formed by mixing polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high density polyethylene, linear low density polyethylene, low density polyethylene and ultra high molecular weight polyethylene, .

In addition, the polymer film base material may be produced by molding various polymeric materials such as polyester in addition to polyolefin to form a film. In addition, the porous polymeric film substrate may have a structure in which two or more film layers are laminated, and each film layer may be formed of a polymer such as polyolefin or polyester described above, or a polymer in which two or more polymers are mixed have.

In addition, the porous polymer film base and the porous nonwoven base material may be formed of a material selected from the group consisting of polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, Polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene, polyetherketone, polyetherketone, polyetherketone, And the like may be used alone or in the form of a mixture thereof.

The thickness of the porous substrate is not particularly limited, but is preferably 5 to 50 占 퐉, and the size of the pores present in the porous substrate should be smaller than that of the polymer binder fiber of the electrode adhesive layer, preferably 0.001 to 50 占 퐉, The porosity is preferably from 01 to 99%.

The porous coating layer may be formed on one surface or both surfaces of the porous polymer substrate, and may include inorganic particles or a binder polymer. According to an embodiment of the present invention, the inorganic particles may be bound to each other by the binder polymer in a state where they are charged and in contact with each other, whereby an interstitial volume may be formed between the inorganic particles And the interstitial volume between the inorganic particles becomes an empty space to form pores.

That is, the binder polymer adheres the inorganic particles to each other so that the inorganic particles can remain bonded to each other, for example, the binder polymer can connect and fix the inorganic particles. According to an embodiment of the present invention, the pores of the porous coating layer may be voids formed by interstitial volumes between the inorganic particles, packed or densely packed) of the surface of the substrate. A path through which lithium ions necessary for operating the battery through the pores of the porous coating layer can be provided.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). Particularly, when inorganic particles having a high dielectric constant are used as the inorganic particles, the dissociation of the electrolyte salt, for example, the lithium salt in the liquid electrolyte, can be increased, and the ion conductivity of the electrolyte can be improved.

For the reasons stated above, the inorganic particles may include high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, or inorganic particles having lithium ion transferring ability or a mixture thereof.

Nonlimiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x Ti _1-x ) O ₃ (PZT, 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O _{3 (PLZT, 0 <x <} 1, 0 <y <1), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, 0 <x <1), Wherein the metal oxide selected from the group consisting of hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ Inorganic particles such as one or a mixture of two or more of them not only exhibit a high dielectric constant characteristic with a dielectric constant of 100 or more but also exhibit piezoelectricity in which a charge is generated when a certain pressure is applied and then a potential is generated, ), It is possible to prevent internal short-circuiting of both electrodes due to an external impact, thereby improving the stability of the electrochemical device.

In addition, the inorganic particles having lithium ion transferring ability mean inorganic particles containing a lithium element and having a function of transferring lithium ions without storing lithium. Non-limiting examples of inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x < lithium aluminum titanium phosphate _{(Li x Al y Ti z (} PO 4) 3, 0 <x <2,0 <y <1,0 <z <3), (LiAlTiP) x O y series glass (glass) (0 < x <4, 0 <y < 13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2,0 <y <3), lithium germanium thiophosphate Mani Titanium (Li _x Ge _y P _z S _{w, 0 <x <4,} 0 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS ₂ (Li _x Si _y S _z , 0 <x <3, 0 <y < ₂ , 0 <z <4) series glass and P ₂ S ₅ (Li _x P _y S _z , 0 <x < y < 3, 0 < z < 7) series glass or a mixture thereof. When the above-mentioned high-permittivity inorganic particles and inorganic particles having lithium ion transferring ability are mixed, their synergistic effect can be doubled.

The inorganic particle size of the porous coating layer is not limited, but it is preferably in the range of 0.001 to 10 탆 for forming a coating layer of uniform thickness and proper porosity.

Further, 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 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 or be 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.

1 is a perspective view schematically showing a pouch case. Referring to FIG. 1, the pouch case may include a lower case 10 and an upper case 20. In this case, the space in which the electrode assembly can be housed may be formed in any one of the upper case and the lower case, or both the upper case and the lower case. Hereinafter, A space may also be formed in the case.

2 is a cross-sectional view of a pouch type secondary battery according to an embodiment of the present invention. Referring to FIG. 2, the pouch case applicable to the present invention includes a lower case 10, an upper case 20, a sealing portion 30, and a welding portion 40.

At this time, the lower case may be formed with an inner space for receiving the electrode assembly, and the upper case may be coupled with the lower case to cover the inner space.

Further, when the electrode assembly is received in the inner space of the lower case, the lower case and the upper case are coupled to each other to form a sealing part at the joints.

And a welding part for sealing the sealing part by connecting the side exposed to the outside of the upper case and the side exposed to the outside of the lower case.

3 is an enlarged view of a sealing part and a weld part included in the pouch type secondary battery according to an embodiment of the present invention.

3A and 3B, the lower case and the upper case may have a structure in which a metal layer 32 and an insulating layer 33 are laminated, respectively. In this case, The metal layers 32 of the metal layers 32 are mutually abutted to form a sealing portion.

In addition, the metal layer of the upper case and the metal layer of the lower case, which are exposed to the outside, can be welded to effectively block water penetrated from the outside.

At this time, only the metal layer may be welded and sealed as shown in FIG. 3A, or both the metal layer and the insulating layer may be welded as shown in FIG. 3B.

4 is an enlarged view of a sealing part and a welded part included in the pouch type secondary battery according to another embodiment of the present invention.

4A and 4B, the lower case and the upper case may have a structure in which a heat-sealable layer 31, a metal layer 32, and an insulating layer 33 are laminated, The heat-sealable layer 31 of the upper case and the heat-sealable layer 31 of the upper case contact each other to form a sealing portion.

At this time, the sealing part is primarily sealed by melting the heat-sealable layer constituting the inner surface of the pouch case by the heat applied from the outside and attaching the upper case and the lower case to each other.

The primary sealing has a problem in that water is permeated due to fusion of the polymer. Conventionally, a method of increasing the sealing area to slow down the permeation rate of water has been used, but there has been a problem that the space utilization rate is lowered.

Therefore, the present invention can fundamentally block moisture permeated from the outside by welding the metal layer of the upper case and the metal layer of the lower case exposed to the outside.

FIG. 4 (a) is a view illustrating a process of welding a heat-sealable layer and a metal layer to seal a sealing portion according to an embodiment of the present invention. At this time, the welding may be performed by welding a metal layer exposed on the side surfaces of the upper case and the lower case, or welding another metal to the side surfaces of the upper case and the lower case.

FIG. 4 (b) shows another embodiment of the present invention in which the heat-sealing layer, the metal layer, and the insulating layer are welded together to weld the sealing portion. In this case, It can be welded in a manner of attaching a separate metal.

As in the above embodiments, the present invention is advantageous in that it is possible to omit the insulating layer removing step, which has been performed in the prior art, by welding using a metal layer exposed on the surface or by adding metal to the side surface.

At this time, the welded portion may be formed of at least one metal selected from the group consisting of stainless steel, aluminum, copper, lead, zinc, magnesium, tin, chromium, brass alloy, phosphor bronze, silicon manganese copper, Lead, tin, bronze, brass, more preferably zinc, tin, and lead.

In addition, the welding method applicable to the present invention can be applied differently according to the metal layer, but applicable methods in the technical field can be applied without limitation, including ultrasonic welding, E-beam welding Or arc welding.

In ultrasonic welding, ultrasonic vibration of 20 KHz to 60 KHz may preferably be applied.

In the laser welding, a CW (continuous wave) laser and an optical system having a laser energy density of preferably 150 kJ / cm 2 to 650 kJ / cm 2 are used to measure a welding speed of 50 to 200 mm / s , And more preferably from 80 to 120 mm / s using a CW laser and an optical system having a laser density of 300 kJ / cm 2 to 500 kJ / cm 2.

In the case of welding using the CW laser in laser welding, the laser oscillation may be modulated to have a constant frequency in order to prevent thermal damage to the welding material due to the heat continuously exposed. In this case, , The modulation frequency may be from 8 Hz to 5 kHz, and the rate at which the laser oscillates during modulation may be between 30% and 90% of the modulation frequency. For example, when a 50% oscillation rate is used for 1 kHz modulation, laser output modulation is performed at 1 ms intervals, 500 us is a state in which the laser oscillates, and 500 us is a state in which laser oscillation is not performed State is repeated.

As the heat-sealable layer applicable to the present invention, any of those used in the related art can be used without limitation, and preferably a polyolefin (such as a copolymer of polyethylene, polypropylene, polyethylene and polypropylene), polycarbonate, polyester (Such as polyethylene terephthalate and polyarylate), polyvinyl chloride, acrylic polymers (polyacrylonitrile and polyacrylate), polyamide (aramid and nylon), cellulose, polybenzoxazole (Polytetrafluoroethylene (Teflon) or the like), and glass fiber, or a composite film structure composed of two or more material layers .

In addition, the insulating layer applicable to the present invention may be any material capable of forming the outermost surface of the pouch case in the art, and may be made of any one of polyester (polyethylene terephthalate, polybutylene terephthalate, A single film made of a material selected from the group consisting of polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, etc.), polycarbonate, and polyamide, or a composite film structure composed of two or more material layers.

In addition, the metal layer applicable to the present invention can be used without limitation in the art, and examples thereof include, but not limited to, alloys of iron, carbon, chromium and manganese, alloys of iron, chromium and nickel, And may have a metal thin film structure made of one material.

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 limited to the disclosed exemplary embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

10: lower case 20: upper case
30: sealing part 31: heat fusion layer
32: metal layer 33: insulating layer
40:

Claims (7)

A pouch type secondary battery comprising an electrode assembly and a pouch case for accommodating the electrode assembly,
A lower case in which the pouch case has an internal space for receiving the electrode assembly;
An upper case coupled to the lower case to cover the inner space;
A sealing portion formed at a portion where the upper case and the lower case are joined to each other; And
And a welding portion connecting the side surface of the upper case and the side surface of the lower case to each other to seal the sealing portion. The method according to claim 1,
Wherein the upper case and the lower case have a structure in which a metal layer-insulating layer is laminated or a structure in which a heat-sealing layer-metal layer-insulating layer is sequentially laminated. The method according to claim 1,
Wherein the welded portion is welded to seal the sealing portion by connecting the metal layers exposed on at least one side of the upper case and the lower case to each other. The method according to claim 1,
Wherein the welded portion is formed by melting at least one metal selected from the group consisting of stainless steel, aluminum, copper, lead, zinc, magnesium, tin, chrome, brass alloy, phosphor bronze, silicon manganese copper, Secondary battery. 3. The method of claim 2,
Wherein the heat-sealable layer is a single film made of any one material selected from the group consisting of a polyolefin, a polycarbonate, a polyvinyl chloride, an acrylic polymer, a polyamide, a cellulose, a polyester, a polybenzoxazole, a fluororesin, And a composite membrane structure composed of two or more material layers. 3. The method of claim 2,
Wherein the insulating layer has a composite film structure composed of a single film made of any one material selected from the group consisting of polyester, polycarbonate, and polyamide, or two or more material layers. 3. The method of claim 2,
Wherein the metal layer has a metal thin film structure made of any one of an alloy of iron, carbon, chromium and manganese, an alloy of iron, chromium and nickel, or aluminum.

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