KR101476040B1 - Pouch-typed lithium secondary battery comprising a separator coated with a gas-adsorbent, large-sized battery module employed with the same - Google Patents

Abstract

The present invention provides a secondary battery including a separator in which a cathode, an anode, an electrolyte, and a coating film containing a gas adsorbent are integrated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a secondary battery including a separator coated with a gas adsorbent, and a middle- or large-sized battery module using the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002]

The present invention relates to a lithium secondary battery including a separator coated with a gas adsorbent.

Lithium secondary batteries have higher energy densities than lead-acid batteries and nickel-cadmium batteries, and are currently used in civilian devices such as video cameras, mobile phones, notebook personal computers, and portable information terminals. In recent years, lithium secondary batteries have attracted attention as electric vehicles and electric power storage batteries due to demands for prevention of air pollution and effective utilization of electric power energy.

However, in a lithium secondary battery mounted in an industrial device such as a notebook type personal computer, a portable information terminal device, and an industrial device such as a power storage system or an electric automobile, the use temperature may be as high as 40 to 80 DEG C A battery having excellent cycle characteristics even at a high temperature is desired. For example, in the case of a lithium secondary battery using a LiMn ₂ O ₄ anode, deterioration of cycle life due to elution of manganese from the positive electrode active material is problematic.

In addition, in the lithium secondary battery, a film-type sheathing material using a polymer film capable of heat fusion instead of a metal container as a sheathing material and a laminate film in which a metal foil is laminated is used, and a thin and lightweight battery can be obtained. Accordingly, there is a growing demand for a pouch type lithium secondary battery.

This can be understood with reference to the following Patent Document 1, and all the contents of Patent Document 1 below are incorporated as the contents of the specification of the present invention.

However, this pouch-type lithium secondary battery is particularly problematic in terms of high-temperature cycle life characteristics. Since the film made of the laminate film used for the exterior material has a lower rigidity than the exterior material such as a metal container or the like, if overcharging or overdischarge is caused by erroneous operation of the electronic device, , The non-aqueous electrolytic solution in the battery is decomposed by heating or the like to generate carbon dioxide gas or the like, thereby deforming the film-type outer casing having low rigidity. As a result, there is a problem that the film-like sheathing material expands like a balloon due to the gas generated in the cell.

Particularly, in a pouch-type lithium secondary battery, unlike a can-type battery, gas generated during high-temperature storage or cycle test affects increase in cell resistance. Therefore, an electrolytic solution which generates a large amount of gas when stored at a high temperature is difficult to apply to a battery even if its performance is good.

Japanese Patent Application Laid-Open No. 08-083596

An object of the present invention is to provide a lithium secondary battery having a long life even in a high temperature environment by suppressing an increase in cell resistance due to gas generated after high-temperature storage or cycle test in a lithium secondary battery, particularly a pouch type battery .

As a means for solving the above problems, the present invention provides a secondary battery comprising a cathode, a cathode and a separator, wherein the separator is coated with molecular sieves having gas-adsorbing properties.

The present invention includes a separation membrane in which a coating film capable of adsorbing gas generated in a high temperature environment is integrated, thereby improving not only the stability but also the pouch type lithium secondary A battery can be manufactured.

1 is a conceptual view showing a basic structure of a general pouch type secondary battery.
2 is a cross-sectional view illustrating the structure of an electrode assembly according to an embodiment of the present invention.
FIG. 3 and FIG. 4 are views showing a separation membrane structure in which a gas adsorbent-containing coating film according to an embodiment of the present invention is integrated.

Hereinafter, the configuration and operation according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description with reference to the accompanying drawings, the same reference numerals denote the same elements regardless of the reference numerals, and redundant description thereof will be omitted.

Specifically, the present invention relates to a positive electrode, a negative electrode,

And a separation membrane in which a gas adsorbent-containing coating film is integrated.

FIG. 1 is a conceptual view showing a basic structure of a general pouch type secondary battery, and FIG. 2 is a cross-sectional view illustrating the structure of an electrode assembly according to an embodiment of the present invention. An embodiment for manufacturing the secondary battery of the present invention will be described with reference to FIGS. 1 and 2.

1, the pouch type secondary battery 1 includes an electrode assembly 10, electrode taps 31 and 32 extending from the electrode assembly 10, electrodes 32 and 33 welded to the electrode taps 31 and 32, Leads 51 and 52, and a battery case 20 for housing the electrode assembly 1. [

The electrode assembly 10 is a power generation element in which an anode and a cathode are sequentially stacked with a separation membrane interposed therebetween, and has a stacked or stacked / folded structure. Of course, the electrode assembly to which the separator according to the present invention is applied is not limited thereto. The electrode tabs 31 and 32 extend from the respective electrode plates of the electrode assembly 10 and the electrode leads 51 and 52 are formed by a plurality of electrode tabs 31 and 32 extending from each electrode plate, Respectively, and a part of the battery case 20 is exposed to the outside. An insulating film 53 is attached to portions of the upper and lower surfaces of the electrode leads 51 and 52 in order to increase the degree of sealing with the battery case 20 and at the same time to ensure an electrically insulated state.

In addition, since a plurality of anode and cathode taps 31 and 32 are integrally joined to form a fused portion, the inner upper end of the battery case 20 is spaced apart from the upper end surface of the electrode assembly 10 by a predetermined distance, The negative taps 31 and 32 are bent in a substantially V shape (the joint between the electrode taps and the electrode lead is also referred to as V-forming 41 and 42). The battery case 20 is made of an aluminum laminate sheet, provides a space for accommodating the electrode assembly 10, and has a pouch shape as a whole. The secondary battery has a structure in which the electrode assembly 10 is housed in the housing portion of the battery case 20 and an electrolyte (not shown) is injected into the battery case 20 and then the outer periphery of the battery case 20 contacting the upper and lower laminate sheets And then heat-sealed.

In the structure of the secondary battery, the structure corresponding to the electrode assembly 10 is a laminate structure of an anode, a cathode, and a separator, and a laminate of various structures may be applied. The electrode assembly according to the present invention includes a jelly-roll (wound type) electrode assembly having a long sheet-like anode and a cathode wound with a separator interposed therebetween, a plurality of positive electrodes and cathodes And a stacked (laminated) electrode assembly in which a separator is interposed therebetween. The stacked structure and the stacked / folded structure are preferable. Since the stacked structure is well known in the art, a description thereof will be omitted herein. Details of the stack / folding structure of the electrode assembly are disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059 and 2001-0082060, the contents of which are incorporated herein by reference. Lt; / RTI >

FIG. 2 illustrates a structure of one embodiment of the electrode assembly described above with reference to FIG. 1, wherein (a) a bipolar ('A-type bi-cell') having an anode / separator / cathode / / Separator / anode / separator / cathode structure ('C-type bi-cell') structure. That is, as shown in FIG. 2A, the bi-cell structure includes a double-sided anode 110, a separator 120, a double-sided cathode 130, a separator 140, and a double- A separator 120, a double-sided anode 110, a separator 140, and a double-sided cathode 160 are successively stacked in this order, (It is an example of the electrode assembly, and it is needless to say that the electrode assembly of all structures in which the pull cell structure or the separator is inserted may be applied to the present invention.)

Here, in one embodiment of the present invention, the separation membranes 120 and 140 applied to the electrode assembly are separation membranes in which a gas absorbing agent-containing coating film is integrated.

Specifically, the gas adsorbent may include a single substance selected from the group consisting of molecular sieves having gas adsorptivity and metal components, or a mixture of two or more thereof.

The term "molecular sieve" as used herein refers to the total amount of a substance having a cavity in its molecule and capable of determining the passage of a substance according to the size of the cavity. It should be noted that the 'molecular sieve' is also called 'molecular sieve'. The name 'molecular sieve' was originally a trade name of synthetic zeolite, It is also used. The term " molecular sieve " of the present invention is not limited to merely zeolite, and includes all materials capable of determining the passage of a substance depending on the size of the cavity and a cavity in the molecule. Examples of the "molecular sieve" of the present invention include zeolite, activated carbon, carbon fiber, porous gel (examples of such gel include textur gel, agarose gel, polyacrylamide gel, etc.) .

Specifically, the molecular sieve according to the present invention may include a single substance selected from the group consisting of silica gel, carbon fiber, porous carbon material, porous metal oxide, porous gel, and zeolite, or a mixture of two or more thereof.

At this time, the metal component of the porous metal oxide may include a single substance selected from the group consisting of zeolite, silica gel, alumina, and molecular sieve, or a mixture of two or more thereof.

The above-mentioned porous carbon material may be selected from the group consisting of carbon molecular sieve activated carbon or a mixture thereof.

Particularly, the molecular sieve according to the present invention is preferably zeolite having a relatively small cavity size and easy to purchase among the above-mentioned molecular sieves. In this case, the zeolite having a fine pore diameter within the range of 0.3 to 0.5 nm is applied . If it is outside this range, there arises a problem that the gas adsorption efficiency is deteriorated.

The metal component having gas adsorptivity according to the present invention may be at least one selected from the group consisting of Ni, Pt, Pd, Ca, Sr, Ba, Ti, A single substance selected from the group consisting of zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo) and tungsten . ≪ / RTI >

In addition, the following structure and materials can be applied to the separation membrane applied to the present invention in the above-described structure.

The separator or separator sheet may be formed of an insulating and / or porous thin film having high ion permeability and mechanical strength. Specifically, the separator or separator sheet generally has a pore diameter of 0.01 to 10 μm and a thickness of 5 To 300 m. Examples of the separator or separator sheet include olefin polymers such as polypropylene, which is resistant to chemicals and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used.

Further, when a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separation membrane. Preferably, a multilayer film produced by a polyethylene film, a polypropylene film, or a combination of these films, or a film made of polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or poly A polyvinylidene fluoride hexafluoropropylene copolymer or the like, or a polymer film for a gel-type polymer electrolyte.

It is preferable that the separation membrane has an adhesive function by heat fusion to form a pull cell or a bi-cell, and the separator sheet does not necessarily have such a function. However, in order to facilitate the winding process, .

In addition, in the present invention, in order to construct a pull cell or a bi-cell, an electrode is disposed in one separator, and the electrode is wound in one direction or wound in a zigzag direction. However, the present invention is not limited thereto. It is also possible to adopt a structure in which a lamination is performed in the form of a stacked layer with a separate separation film interposed between the electrodes.

The separation membrane interposed between the anode and the cathode of the separator sheet or cell is not particularly limited as long as it exhibits insulation and has a porous structure capable of moving ions, and the separation membrane and the separation membrane sheet may be the same material or not It is possible.

In the meantime, the present invention encompasses all of technical points that can realize the effect of gas adsorption by integrating the gas adsorbent-containing coating film in a pattern structure on the separation membrane.

FIG. 3 illustrates an embodiment of a separation membrane 120, 140 coated with molecular sieve according to an embodiment of the present invention. Specifically, the molecular sieve may be formed in a pattern structure in which a part of the region S of the separation membrane 120 is exposed. That is, by forming the molecular sieve such that a part of the separation membrane is exposed, it is possible to increase the bonding property with the anode and the cathode material of the electrode assembly and maximize the gas absorption efficiency by enlarging the surface area of the coating film containing the gas adsorbent to be.

As shown in FIG. 3, the pattern may be formed in such a manner that a part of the separation area S is exposed and the rest of the separation area is covered. S, and the remaining separation membrane regions are all exposed. The shape of such a pattern can be freely deformed according to the design.

Alternatively, when the gas adsorbent-containing coating film is integrally formed on the separation membrane as shown in Fig. 4, it can be realized in a mesh-like structure in which line-shaped patterns are arranged to be spaced in either direction or line-shaped structures are crossed. In particular, in the case of the mesh-type structure, the region where the separation membrane is exposed is formed, thereby increasing the bonding property with the anode and cathode materials forming the electrode assembly, and maximizing the gas absorption efficiency by enlarging the surface area of the coating film containing the gas adsorbent.

It is needless to say that the pattern formation structure is not limited thereto, but may be implemented by deforming a polygonal, circular, elliptic, or the like in a region where the isolation region is exposed in various shapes and mesh types.

Hereinafter, the specific materials and constitutional characteristics of the constituent elements of the electrode assembly formed through the separation membrane in the present invention will be described. In the present invention, the unit electrode is divided into a conventional positive electrode or negative electrode, and the pull cell and the bi-cell are manufactured by a conventional method in which the positive electrode and the negative electrode are mutually bonded with a separator interposed therebetween.

Anode structure

Specifically, the anode is prepared by applying a mixture of a cathode active material, a conductive material and a binder on a cathode current collector, followed by drying and pressing, and if necessary, a filler may be further added to the mixture.

[Anode collector]

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

[Cathode active material]

The cathode active material may be a lithium secondary battery, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ wherein x is 0 to 0.33, LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _{1 - x} M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); Formula _{LiMn 2 - x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 to 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds, Fe ₂ (MoO ₄ ) ₃ , and the like, but are not limited thereto.

The conductive material is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

Cathode structure

The negative electrode is prepared by applying, drying and pressing an anode active material on an anode current collector, and may optionally further include a conductive material, a binder, a filler, and the like as described above.

[Cathode collector]

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

[Negative electrode active material]

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1 - x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The secondary battery according to the present invention can be applied not only to a middle- or large-sized battery module having a unit battery, but also to a battery pack including a battery module, including a power tool; An electric vehicle selected from the group consisting of Electric Vehicle (EV), Hybrid Electric Vehicle (HEV), and Plug-in Hybrid Electric Vehicle (PHEV); E-bike; An e-scooter; Electric golf cart; Electric truck; And an electric commercial vehicle.

The middle- or large-sized battery module is configured to provide a large-capacity large-capacity battery by connecting a plurality of unit cells in a serial manner or a serial / parallel manner, which is well known in the art and thus will not be described herein.

In the foregoing detailed description of the present invention, specific examples have been described. However, various modifications are possible within the scope of the present invention. The technical idea of the present invention should not be limited to the embodiments of the present invention but should be determined by the equivalents of the claims and the claims.

1: Pouch type secondary battery
10: electrode assembly
20: Battery case
31, 32: electrode tab
41, 42: V-forming section
51, 52: electrode lead
53: Insulation film
110, 150: double-sided anode
120, 140: Membrane
130, 160: double-sided cathode
S: Separator exposure area
S1, S2: molecular sieve pattern

Claims (15)

Anode, cathode, electrolyte, and
A secondary battery comprising a separation membrane in which a gas adsorbent-containing coating film is integrated,
Wherein the gas adsorbent-containing coating film is integrated in a line type pattern that exposes a part of the separation membrane, or a mesh type pattern in which line type patterns are crossed. The method according to claim 1,
Wherein the gas adsorbent comprises a single substance selected from the group consisting of molecular sieves having gas adsorptivity and metal components or a mixture thereof. The method of claim 2,
Wherein the molecular sieve includes a single material selected from the group consisting of silica gel, carbon fiber, porous carbon material, porous metal oxide, porous gel, and zeolite, or a mixture of two or more thereof. The method of claim 3,
Wherein the porous carbon material includes a single material selected from the group consisting of carbon molecular sieve and activated carbon, or a mixture thereof. The method of claim 3,
Wherein the metallic material of the porous metal oxide comprises a single material selected from the group consisting of zeolite, silica gel, alumina, and molecular sieve, or a mixture of two or more materials. The method of claim 2,
Wherein the molecular sieve is a zeolite. The method of claim 6,
Wherein the zeolite has a fine pore diameter within a range of 0.3 nm to 0.5 nm. The method of claim 2,
The metal component may be at least one selected from the group consisting of Ni, Pt, Pd, Ca, Sr, Ba, Ti, Zr, (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo) and tungsten (W) or a mixture of two or more thereof. The method according to claim 1,
Wherein the separation membrane is a separation membrane or a separation membrane sheet including pores having a diameter of 0.01 to 10 mu m. The method of claim 9,
Wherein the separation membrane is a sheet or nonwoven fabric made of an olefin-based polymer, glass fiber, or polyethylene. delete delete The method according to claim 1,
The secondary battery
A positive electrode having a positive electrode slurry layer coated on the positive electrode collector;
A negative electrode having a negative electrode slurry layer coated on the negative electrode collector;
Electrolyte; And
And a separator film in which a coating film containing a gas adsorbent interposed between the anode and the cathode is integrated, the unit cell comprising at least one unit cell. 14. The method of claim 13,
Wherein the unit cell is a bi-cell or a pull-cell. A middle- or large-sized battery module comprising at least two or more secondary batteries according to claim 1 or 13.

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