KR101484318B1 - Pouch for secondary battery and Secondary battery using the same - Google Patents

Abstract

The present invention provides a pouch exterior material comprising a inner layer / a metal layer / an outer layer, wherein the inner layer is coated with a hydrophobic inorganic layer, and a secondary battery comprising the same, wherein the interior layer of the pouch exterior material comprises a hydrophobic inorganic layer It is possible to prevent not only moisture penetration but also electrolyte penetration into the metal layer, thereby solving the problem that the insulation resistance is destroyed, and as a result, the safety of the battery can be improved as a result.

Pouch * Outer material * Hydrophobic inorganic layer * Insulation resistance * Moisture penetration * Secondary battery

Description

[0001] The present invention relates to a pouch type secondary battery and a secondary battery using the same,

The present invention further includes a hydrophobic inorganic layer in the inner layer of the pouch outer cover made up of the inner layer / metal layer / outer layer to prevent the performance of the battery from degrading due to moisture penetration in the pouch type secondary battery, And a pouch type secondary battery including the same.

As the use of portable electric appliances such as video cameras, portable phones, and portable PCs is being activated, the importance of secondary batteries, which are mainly used as driving power sources, is increasing. In particular, the lithium secondary battery has a higher energy density per unit weight and can be rapidly charged as compared with conventional lead-acid batteries and other secondary batteries such as nickel-cadmium batteries, nickel-hydrogen batteries and nickel-zinc batteries. It is actively proceeding.

Unlike conventional primary batteries, which can not be charged, secondary batteries capable of charging and discharging are under active research in the development of advanced fields such as digital cameras, cellular phones, notebook computers and hybrid vehicles. Examples of the secondary battery include a nickel-cadmium battery, a nickel-metal high-hydride battery, a nickel-hydrogen battery, and a lithium secondary battery. Among them, the lithium secondary battery is used as a power source of a portable electronic device at an operating voltage of 3.6 V or more, or several series are connected in series to be used in a high-output hybrid vehicle. Compared with a nickel-cadmium battery or a nickel-metal hydride battery The operating voltage is three times higher and the energy density per unit weight is also excellent.

The lithium secondary battery can be classified into a lithium ion battery using a liquid electrolyte and a lithium ion polymer battery using a polymer solid electrolyte depending on the type of electrolyte. The lithium ion polymer battery can be divided into a fully solid lithium ion polymer battery containing no electrolytic solution and a lithium ion polymer battery using a gel polymer electrolyte containing an electrolyte depending on the kind of polymer solid electrolyte.

In the case of a lithium ion battery using a liquid electrolyte, it is usually used in a form in which a cylinder or a rectangular metal can is used as a container and welded and sealed. Since the can type secondary battery using such a metal can as a container is fixed in shape, there is a disadvantage that it restricts the design of an electrical product using the metal can as a power source, and it is difficult to reduce the volume. Therefore, a pouch-type secondary battery in which two electrodes, a separator, and an electrolyte are put in a film-made pouch and sealed is developed and used.

1, the pouch exterior member 100 is formed of a polyolefin resin layer (Polyolepin Layer), which is an inner layer 11 having a thermal adhesiveness in order and serving as a sealing material, a base material for maintaining mechanical strength, Layer structure in which an aluminum layer (AL / Aluminum Layer) serving as a metal layer 13 serving as a layer, an outer layer 15 serving as a base material and a protective layer (usually a nylon layer) are laminated. Commonly used as a polyolefin-based resin layer is CPP (Casted Polypropylene).

2 shows a conventional lithium ion polymer battery 200. The lithium ion polymer battery 200 is divided into a lower portion 20 having a receiving portion 21 and an upper portion 10 covering the lower portion 20, The electrode assembly 30 housed in the accommodating portion 21 is formed by winding the positive electrode 31 and the negative electrode 35 and the separator 33 in layers. The tabs 37 and 38 are drawn out from the respective electrodes and the tapes 39 are attached to the tabs 37 and 38 at portions overlapping the sealing portions 23. [

3, when the inner layer of the upper sheet 10 and the inner sheet of the lower sheet 20 are thermally fused, the CPP constituting the inner layer melts and the sealing portions 23 and 24 ).

However, when a crack is generated or broken in the CPP layer as the inner layer, the electrolytic solution or moisture from the outside penetrates into the metal layer of the pouch exterior material, and the electrical insulation resistance is destroyed.

In a pouch type lithium secondary battery, sealing of the casing is a very important issue, but due to the characteristics of the pouch, moisture penetrates into the sealing part made of polymer. Penetration of foreign matter such as moisture from the outside causes deterioration of performance such as accelerating the corrosion of the electrode assembly, the tab and the casing, or damaging the active material of the cathode / anode.

Further, as the use time of the battery becomes longer, the moisture penetration from the outside becomes a factor that deteriorates the performance of the battery in the long term, and measures are urgently required.

Accordingly, in the present invention, in order to seal the pouch case, the present invention solves various problems of the conventional secondary battery, which is caused by infiltration of moisture or electrolytic solution from the outside, thereby improving the performance of the battery.

Accordingly, the present invention solves the problem of deterioration of battery performance by preventing moisture permeation from the outside by applying a hydrophobic inorganic layer to a CPP layer constituting an inner layer in a conventional pouch exterior material.

Accordingly, it is an object of the present invention to provide a pouch exterior material which can reduce water penetration from the outside and destruction of electrical insulation resistance, and can suppress water and electrolytic solution penetration due to hydrophobic properties even if internal layer breakage has occurred have.

Another object of the present invention is to provide a pouch-type secondary battery having improved battery performance by using a pouch exterior member capable of preventing moisture penetration from the outside as described above.

As in the present invention, by coating a hydrophobic inorganic layer on the inner layer of the pouch case, it is possible to prevent not only water penetration but also electrolyte penetration into the metal layer, thereby solving the problem that the insulation resistance is destroyed. As a result, have.

In order to achieve the above object, the pouch for a secondary battery of the present invention is a pouch outer casing made of an inner layer / a metal layer / an outer layer, wherein the inner layer is coated with a hydrophobic inorganic layer.

According to another aspect of the present invention, there is provided a pouch-type secondary battery including the pouch outer casing.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

4 is a pouch outer sheath 400 according to an embodiment of the present invention in which a pouch outer sheath made of inner layer 11 / metal layer 13 / outer layer 15, Thereby forming a hydrophobic inorganic layer 16.

The hydrophobic inorganic material layer 16 is _{SiO 2, Al 2 O 3,} MgO, BaTiO 3, and comprises a hydrophobic inorganic substance selected from the group consisting of ZrO ₂ and ZnO, but are not limited thereto. The average particle diameter of the hydrophobic inorganic material is preferably 1 to 500 nm.

The hydrophobic inorganic material layer is preferably formed to a thickness of 10 to 100 탆 in terms of an appropriate adhesion thickness after battery formation.

Since the inner layer 11 made of CPP is thermally fused and adhered to the inner layer of the pouch outer cover according to the present invention by incorporating the hydrophobic inorganic layer, the hydrophobic inorganic layers are thermally fused to each other, There are advantages.

In addition, the hydrophobic inorganic material layer is superior in physical strength and the like compared to the CPP polymer constituting the inner layer, so that it is expected that the probability of occurrence of cracks or defects in the pouch outer material is relatively small even from the outside. Further, even if cracks or defects are generated in the outer surface of the hydrophobic inorganic layer, since the inner layer made of CPP is formed, external problems such as moisture and electrolytic solution reaching the inner metal layer and causing electrical short-circuit .

The pouch for a secondary battery according to the present embodiment includes three layers of an inner layer, a metal layer, and an outer layer made of nylon, except for the hydrophobic inorganic layer, and more functional layers may be further provided if necessary. It can also be formed of many other alternative material layers. For example, the CPP layer may be replaced by a layer of a material selected from the group consisting of polypropylene, polypropylene, polyethylene, ethylene propylene copolymer, polyethylene and acrylic acid copolymer, and copolymers of polypropylene and acrylic acid, which are other polyolefin resins.

The metal layer may be made of an alloy of Fe, C, Cr and Mn, an alloy of Fe, C, Cr and Ni, Al), and among them, aluminum is most preferable.

The total thickness of the pouch film is usually 40 to 120 占 퐉, and the outer layer, the inner layer and the metal layer are preferably 10 to 40 占 퐉 and 20 to 100 占 퐉, respectively.

The present invention also provides a secondary battery in which an electrode assembly in which a cathode and an anode are insulated and wound with a separator interposed therebetween is housed in a pouch exterior member having the above-described structure.

An electrode assembly according to the present invention comprises a positive electrode comprising a positive electrode active material, a negative electrode including a negative electrode active material, and a separator.

Specifically, the anode is prepared, for example, by coating a mixture of a cathode active material, a conductive agent and a binder on a cathode current collector, and then drying the cathode active material. Optionally, a filler may be further added to the mixture.

The cathode active material according to the present invention is a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; A lithium manganese oxide (LiMnO ₂ ) such as LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, etc. represented by the formula Li _{1 + x} Mn _{2 -x} O ₄ (where x is 0 to 0.33); 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 nickel-situ type lithium nickel oxide represented 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) oxide); Formula _{LiMn 2-x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which part of the lithium in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) _3, or a composite oxide formed by a combination of these materials, and the like, may be mixed with a compound containing a lithium intercalation material as a main component.

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 change in the battery, and may be formed of a material such as stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel 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.

The conductive agent 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 agent is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite and 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 oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component which assists in binding of the active material and the conductive agent and bonding to the current collector, and is usually added in an amount of 1 to 50% by weight 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.

The negative electrode is manufactured by applying a negative electrode material on a negative electrode collector and drying the same, and may further include the above-described components as needed.

The negative electrode 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 conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, 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.

The negative electrode material includes amorphous carbon or regular carbon, and specifically carbon such as hard graphitized carbon and graphite carbon; Li _x Fe ₂ O ₃ (0? _X? 1), LixWO ₂ (0? _X? 1), Sn _x Me _1-x Me _y O _z (Me: Mn, Fe, Pb, , B, P, Si, Group 1, Group 2 and Group 3 elements of the periodic table, Halogen, 0 <x <1> 1 <y> 3, 1 <z <8); 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.

A polyolefin-based separator commonly known as a separator for insulating the electrodes between the anode and the cathode or a composite separator having an organic-inorganic composite layer formed on the olefin-based substrate may be used without particular limitation.

An electrode current collector having the above structure is housed in a pouch case, and then an electrolyte is injected to manufacture a battery.

The electrolyte according to the present invention is a lithium salt-containing non-aqueous electrolyte, which is composed of a nonaqueous electrolyte and lithium. As the non-aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte and the like are used.

Examples of the nonaqueous electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, tetrahydroxyfuran

the organic solvent is selected from the group consisting of tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, Diethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl pyrophosphate, ethyl propionate And the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation groups, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6 , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carboxylate lithium, 4-phenylborate lithium, have.

For the purpose of improving charge / discharge characteristics, flame retardancy, etc., non-aqueous electrolytes may be used in the form of, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. are added It is possible. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

Meanwhile, the pouch-type secondary battery is preferably a lithium secondary battery, but the present invention is not limited thereto.

FIG. 1 shows a structure of a pouch exterior material having a three-layer structure of a normal inner layer / metal layer / outer layer,

2 is a perspective view of a pouch type secondary battery,

3 is an example of a pouch-

Fig. 4 shows the structure of the pouch exterior material according to the present invention.

Claims (8)

Wherein the inner layer is coated with a hydrophobic inorganic layer, and the hydrophobic inorganic material is at least one selected from the group consisting of MgO, BaTiO ₃ , ZrO _2, and ZnO Wherein the pouch is made of at least one material selected from the group consisting of polyolefins, polyolefins, polyolefin resins, The battery case according to claim 1, wherein the hydrophobic inorganic layer has a thickness of 10 to 100 탆. The battery case according to claim 1, wherein the hydrophobic inorganic material has an average particle diameter of 1 to 500 nm. delete 2. The composition of claim 1, wherein the inner layer comprises at least one of CPP, a polypropylene-butylene-ethylene terpolymer, a chlorinated polypropylene, a polyethylene, an ethylene propylene copolymer, a copolymer of polyethylene and an acrylic acid copolymer, and a copolymer of polypropylene and acrylic acid Wherein the pouch outer material is at least one selected from the group consisting of polyolefins and polyolefins. The method of claim 1, wherein the metal layer is formed of an alloy of iron (Fe), carbon (C), chromium (Cr), and manganese (Mn), iron (Fe), carbon (C), chromium (Cr), and nickel , And aluminum (Al). &Lt; / RTI &gt; The battery case of claim 6, wherein the metal layer is aluminum. A secondary battery comprising a pouch exterior member of the battery according to any one of claims 1 to 3 and 5 to 7.

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