KR102355197B1 - The method for lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

The present invention relates to a method for manufacturing a lithium secondary battery and a lithium secondary battery manufactured using the same, and more particularly, to (S1) inserting an electrode assembly into a thermoplastic polymer inner protective film and sealing the electrode assembly; and (S2) forming an outer protective layer on the inner protective film by 3D printing; has a significantly improved energy density without limitation of the thickness and shape of the outer material that can be implemented by including; It relates to a method for manufacturing a lithium secondary battery capable of being manufactured, and to a lithium secondary battery manufactured using the same.

Description

Method for manufacturing a lithium secondary battery and a lithium secondary battery manufactured thereby

The present invention relates to a method for manufacturing a lithium secondary battery and to a lithium secondary battery manufactured by the same.

Recently, compact and lightweight electric/electronic devices such as mobile phones, notebook computers, and camcorders have been actively developed and produced, and these electric/storage devices are designed to operate in places where a separate power source is not provided. It has a built-in battery pack. In addition, vehicles using motors such as hybrid vehicles (HVs) and electric vehicles (EVs) are being developed and produced, and a battery pack capable of driving the motors is also built-in in these vehicles. The above-described battery pack includes at least one battery to output a voltage of a predetermined level in order to drive an electric/storage device or a vehicle for a predetermined time.

In consideration of the economical aspect, recently, a rechargeable battery that can be charged/discharged is employed in a battery pack. The secondary battery typically includes a nickel-cadmium (Ni-Cd) battery, a nickel-hydrogen (Ni-MH) battery, a lithium (Li) battery, and a lithium secondary battery such as a lithium ion (Li-ion) battery.

Of these, lithium secondary batteries have been researched and developed since the early 1970s, and in 1990, lithium ion batteries using carbon as an anode instead of lithium metal were developed and put to practical use. It has the highest sales elongation among secondary batteries and is 30 to 40% lighter than nickel-metal hydride batteries, enabling weight reduction. In addition, the lithium secondary battery has the highest unit cell voltage (3.0 to 3.7V) and excellent energy density among existing secondary batteries, and thus may have characteristics optimized for mobile devices.

These lithium secondary batteries are generally classified into liquid electrolyte batteries and polymer electrolyte batteries according to the type of electrolyte. A battery using a liquid electrolyte is called a lithium ion battery, and a battery using a polymer electrolyte is called a lithium polymer battery. In addition, the exterior material of the lithium secondary battery may be formed in various types, and typical types of exterior materials include a cylindrical type, a prismatic type, and a pouch. An electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed therebetween is stacked or wound is provided inside the exterior material of the lithium secondary battery.

Recently, as the field of application of the lithium secondary battery has been rapidly expanded, the demand for a lithium secondary battery having a high energy density is increasing. In order to solve this problem, it is necessary to increase the number of unit cells. In the case of a pouch-type secondary battery, when the thickness of the electrode assembly is increased, there is a problem in that the exterior material is cracked or torn.

Korean Patent Application Laid-Open No. 2014-0134916 discloses a step of forming a receiving groove on one side of a pouch fabric; mounting an electrode assembly inside the receiving groove of the pouch fabric; and sealing the first sealing part of the pouch fabric on which the electrode assembly is mounted, comprising: spraying a waterproof resin composition on the formed first sealing part after the sealing step; and curing the waterproof resin composition to form a second sealing part is disclosed with respect to a method for manufacturing a pouch for a secondary battery characterized in that it comprises, but did not present an alternative to the above-mentioned problems.

Korean Patent Publication No. 2014-0134916

An object of the present invention is to provide a method for manufacturing a lithium secondary battery capable of manufacturing a lithium secondary battery having improved energy density.

An object of the present invention is to provide a lithium secondary battery manufactured by the method for manufacturing the lithium secondary battery.

The present invention comprises the steps of (S1) inserting an electrode assembly into a thermoplastic polymer inner protective film and sealing; and (S2) forming an outer protective layer on the inner protective layer by 3D printing;

According to one embodiment of the present invention, the external protective layer may provide a method of manufacturing a lithium secondary battery formed of a single layer or a plurality of layers.

According to one embodiment of the present invention, the outer protective layer may be formed of a resin layer, or may provide a method of manufacturing a lithium secondary battery formed including a metal layer and a resin layer.

According to one embodiment of the present invention, there may be provided a method of manufacturing a lithium secondary battery in which the external protective layer is formed including an inorganic filler.

In addition, according to one embodiment of the present invention, the (S1) step may provide a method of manufacturing a lithium secondary battery further comprising a formation process, wherein the (S1) step is a gas after the formation process It is possible to provide a method of manufacturing a lithium secondary battery further comprising a discharging process.

According to the manufacturing method of the lithium secondary battery of the present invention, it is possible to manufacture a lithium secondary battery having a significantly improved energy density without limiting the thickness and shape of the material that can be implemented.

According to the manufacturing method of the lithium secondary battery of the present invention, it is possible to manufacture a lithium secondary battery capable of effectively preventing moisture penetration even without using a conventional pouch case. Through this, durability of the secondary battery may be improved, and thus safety and long-term storage characteristics of the battery may be improved.

1 is a flowchart of a method for manufacturing a lithium secondary battery according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a lithium secondary battery manufactured according to an embodiment of the present invention.

The present invention comprises the steps of (S1) inserting an electrode assembly into a thermoplastic polymer inner protective film and sealing; and (S2) forming an outer protective layer on the inner protective film by 3D printing; has a significantly improved energy density without limiting the thickness of the outer material that can be implemented by including; It relates to a method for manufacturing a possible lithium secondary battery and a lithium secondary battery manufactured using the same.

1 is a flowchart schematically illustrating a method of manufacturing a lithium secondary battery according to an embodiment of the present invention, and FIG. 2 is a schematic cross-section of a secondary battery manufactured according to the method of manufacturing a lithium secondary battery of the present invention .

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the above-described contents of the present invention, so the present invention is described in such drawings It should not be construed as being limited only to the matters.

Manufacturing method of lithium secondary battery

The lithium secondary battery manufacturing method of the present invention includes first inserting the electrode assembly 10 into the thermoplastic polymer inner protective film 20 and sealing the electrode assembly (S1).

The electrode assembly 10 according to the present invention may be a unit cell with a separator interposed between the positive electrode and the negative electrode or an aggregate of a plurality of unit cells, but is not necessarily limited thereto. In addition, the structure of the electrode assembly 10 may be applied without a particular limitation on the structure applied to the field.

The thermoplastic polymer inner protective film 20 according to the present invention is provided with a receiving part for the electrode assembly 10 therein for disposition and protection of the electrode assembly 10, and the protective film 20 is the electrode assembly 10. It must be formed of a thermoplastic polymer that can be melted by heat in order to seal it with heat applied to the periphery after insertion. Accordingly, the thermoplastic polymer inner protective film 20 is fused to each other and sealed with the electrode assembly 10 mounted thereon. Since the inner protective film 20 made of a thermoplastic polymer has sufficient ductility unlike the conventional pouch, cracks or tears do not occur even when the electrode assembly 10 is inserted and then sealed.

The thermoplastic polymer inner protective film 20 exhibits thermoplasticity and can be sealed without any side reaction with the electrolyte. It may be a composite membrane structure made of two or more materials. As the thermoplastic polymer inner protective film 20, polypropylene is most preferable in terms of heat sealing and battery weight reduction, and polypropylene is used as a single layer of homo polypropylene, modified polypropylene, or a mixture thereof, or a structure in which these are laminated. can The total thickness of the thermoplastic polymer inner protective layer 20 may be, for example, 5 μm or more, and 20 to 100 μm may be appropriate, but is not limited thereto.

The method for sealing the electrode assembly 10 after inserting it into the thermoplastic polymer inner protective film 20 is generally known in the art and may be applied without particular limitation as long as it does not deviate from the purpose of the present invention, but the polymer inner protective film ( 20) Considering the characteristics of the material, the most preferable method is to melt the polymer inner protective film 20 by applying heat and then bond. In addition, the temperature range of the heat applied at this time depends on the melting point range of the polymer constituting the inner protective film 20 .

More specifically, the electrode assembly 10 may be inserted into the inner protective film 20 of the thermoplastic polymer, and an electrolyte may be injected into the inner protective film 20 and then sealed.

According to one embodiment of the present invention, the step (S1) may further include a formation process, and according to another embodiment of the present invention, the step (S1) is a gas discharge process after the formation process. may include more.

The formation step is a process of activating a battery by repeating charging and discharging. Since gas is generated while charging the battery for activation during the chemical conversion process, the generated gas is discharged and sealed to stabilize the battery activated in the chemical conversion step.

The conditions of the chemical conversion process and/or the gas discharge process are not particularly limited, and can be adjusted within a conventional range known in the art. As a specific example, it is allowed to stand for 10 hours after injection so that the battery case 10 is evenly impregnated with the electrolyte, and then, after charging the battery for activation and removing the generated gas, the battery case 10 may be left for 12 hours, activated charging, etc. may be performed again.

Then, the lithium secondary battery manufacturing method of the present invention includes the step of forming the outer protective layer 30 on the inner protective film 20 by 3D printing.

In the case of increasing the thickness of the casing surrounding the outer portion of the case into which the electrode assembly is inserted in order to increase the energy density of the secondary battery during the manufacturing process of the conventional lithium secondary battery, there is a problem in that the casing material is stretched and torn or cracked.

The present invention uses a 3D printing method in the process of forming the outer protective layer 30 on the thermoplastic polymer inner protective film 20 into which the electrode assembly 10 is inserted, thereby enclosing the electrode assembly 10. The inner protective film 20 The outer protective layer 30 can be directly formed on the outer circumferential surface of the unit without a special molding process. Therefore, the present invention is not limited by the thickness and shape of the exterior material, and the battery can be manufactured without limitation in size or thickness to correspond to the outer shape of the electrode assembly 10 . Therefore, it is possible to solve the problem of cracking or tearing of the conventional pouch battery, and it is possible to provide a battery having a high energy density.

In the present specification, the exterior material 40 is a concept including both the thermoplastic polymer inner protective film 20 and the outer protective layer 30 .

The method of forming the outer protective layer 30 on the polymer inner protective film 20 by the 3D printing technique is not particularly limited as long as it is a 3D printing method capable of forming the outer protective layer 30 on the inner protective film 20, For example, it can be Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), 3 Dimension Printing (3DP), Laminated Object Manufacturing (LOM), Polyjet, Digital Light Processing (DLP), Stereolithography (SLA), etc. and a specific application method may vary depending on the material constituting the outer protective layer 30 .

The external protective layer 30 according to the present invention not only prevents external moisture, gas, etc. from penetrating into the electrode assembly 10 side, but also serves to improve the insulating function and mechanical strength of the exterior material 40 .

According to one embodiment of the present invention, the outer protective layer 30 may be formed of a plurality of layers, and in this case, each layer may be the same or different layers.

When the outer protective layer 30 according to the present invention is formed of a plurality of layers, the outer protective layer 30 may include a metal layer 50 and a resin layer 60 .

The metal layer 50 can be used for 3D printing, and as a material applicable to the exterior material of a secondary battery, if it has excellent thermal conductivity, it can be used without particular limitation on its type, and specifically, aluminum, aluminum alloy, copper, etc. can be used. have.

The resin layer 60 serves to prevent the metal layer 50 from being electrically connected to the outside. The secondary battery should be electrically connected to the outside only through the electrode lead of the electrode assembly 10 , and when the metal layer 50 is directly electrically connected, the safety of the secondary battery is impaired. In particular, when the electrode lead of the electrode assembly 10 is short-circuited through the metal layer 50 , there is a risk of explosion of the secondary battery, so the resin layer 60 serves to protect the metal layer 50 .

The resin layer 60 is usable for 3D printing, and as long as it is a material applicable to the exterior material of the secondary battery, it may be used without any particular limitation on its type.

According to another embodiment of the present invention, the outer protective layer 30 may be formed by the resin layer 60 alone. The resin used for 3D printing has relatively high hardness and/or strength due to the characteristics of 3D printing, and in the present invention, may be applied alone to the outer protective layer 30 .

According to one embodiment of the present invention, the outer protective layer 30 may be formed including an inorganic filler, and in particular, the inorganic filler included in the resin layer 60 maximizes moisture penetration prevention and protects the exterior material (40). It is preferable in terms of hardness improvement, and in this case, it is particularly preferable that the inorganic filler is uniformly dispersed throughout the resin layer 60 .

The type of inorganic filler is not particularly limited as long as it is within the scope not departing from the purpose of the present invention as generally used in the art, and specific examples include silicon (Si), aluminum (Al), zirconium (Zr), zinc ( Zn), magnesium (Mg), zeolite, and the like. Each of these may be used alone or in combination of two or more, and it is also possible to use a metal oxide or a metal nitride including the aforementioned alone or two or more kinds of elements.

The average particle diameter of the inorganic filler may be, for example, 0.5 to 50 μm, preferably 2 to 20 μm, but is not necessarily limited thereto.

lithium secondary battery

In addition, the present invention provides a lithium secondary battery manufactured by the method for manufacturing a lithium secondary battery described above.

In the case of the conventional pouch-type lithium secondary battery, the thickness did not exceed 18 mm due to the reliability problem of the packaging material (pouch), but the lithium secondary battery of the present invention does not have restrictions on the thickness and shape of the packaging material 40, so significantly improved energy density can have

In addition, according to an embodiment of the present invention, when the resin layer 60 is formed to include an inorganic filler, the hardness of the lithium secondary battery casing 40 can be significantly improved.

10: electrode assembly
20: thermoplastic polymer inner protective film
30: outer protective layer
40: exterior material
50: metal layer
60: resin layer

Claims (8)

(S1) inserting and sealing the electrode assembly in the inner protective film of the thermoplastic polymer; and
(S2) After inserting and sealing the electrode assembly into the inner protective film of the thermoplastic polymer, forming an outer protective layer including a metal layer and a resin layer on the inner protective film of the thermoplastic polymer by 3D printing, a lithium secondary battery manufacturing method. delete delete delete The method according to claim 1, wherein the resin layer is formed to include an inorganic filler, the manufacturing method of a lithium secondary battery. The method according to claim 1, wherein the step (S1) further comprises a formation process. The method according to claim 1, wherein the step (S1) further comprises a gas discharging process after the formation process. A lithium secondary battery manufactured by the method of any one of claims 1 and 5 to 7.

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