KR101471666B1 - Wrapping material for Secondary Batteries and Secondary Batteries comprising the same - Google Patents

Abstract

The present invention provides a casing of a secondary battery including a non-combustible coating layer and a secondary battery including the same.

The outer layer itself constituting the casing of the secondary battery may be formed of a nonflammable coating layer or a nonflammable coating layer may be formed on at least one surface of the outer layer as in the present invention to deteriorate battery performance from heat generated by overcharging or external ignition sources. It is possible to provide an excellent flame retardancy without the application of heat. Further, the outer appearance of the battery can be kept constant by applying the outer surface of the battery to the non-combustible coating layer.

Non-flammable coating * Secondary battery * Outer material * Outer layer * Flame retardant

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an outer casing for a secondary battery and a secondary battery including the same,

The present invention relates to a casing for a secondary battery including a non-combustible coating layer and a secondary battery comprising the same. More specifically, the outer layer constituting the casing of the secondary battery may be formed of a non-combustible coating layer, Provided is a secondary battery excellent in flame retardancy without deteriorating battery performance from heat generated by overcharge or an external ignition source by forming a nonflammable coating layer.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Many researches have been conducted on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries. .

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 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.

One of the biggest problems in such a lithium secondary battery is low safety. Safety of existing lithium secondary batteries is one of the most important issues that are continuously raised after commercialization. One of the problems is that the battery is exposed to a thermal shock due to external heating, and is subjected to various environments such as physical deformation The electrolytic solution in the battery is decomposed or seriously ignited to cause an explosion, thereby causing a serious problem in safety of the battery.

Various methods have been proposed to prevent overcharge, which is the cause of the ignition hazard, and to prevent internal short-circuit due to physical deformation. However, despite these preventive measures, measures are required to prevent ignition, or at least to inhibit its progress when ignition is initiated. The risk of ignition is particularly serious in large capacity batteries.

BACKGROUND ART In many fields, a technique of adding a flame retardant to a part of a material for the purpose of preventing and suppressing ignition is widely used. For example, a flame retardant added to a plastic composite suppresses ignition by generating a fire-extinguishing gas or melting and forming a film that blocks oxygen on the surface of the composite. Thus, the use of flame retardants in terms of ignition prevention and inhibition has proven to be very effective.

In the field of batteries, many methods have been proposed for preventing and suppressing ignition through the use of such a flame retardant. For example, JP-A-8-84870 discloses a method of adding phosphoric acid ester to an electrolytic solution, and Japanese Patent Laid-Open Publication No. 1999-154535 discloses a method of incorporating ammonium phosphate into a cathode or an electrode. Although these methods actually provide excellent ignition inhibiting ability, they are directly added to the main functional elements of the battery, so that deterioration of the battery performance can not be avoided.

Therefore, there is a high need for a technique capable of exhibiting an excellent flame retarding effect by the use of a flame retardant without being directly added to an electrolytic solution, a cathode, or an anode active material.

Accordingly, the present invention has been made to solve the problems in the related art related to the safety of the lithium secondary battery as described above.

In the present invention, in a casing of a lithium secondary battery comprising an inner layer, a metal foil layer and an outer layer, at least one side of the outer layer may be coated with a nonflammable polymer material to form a separate nonflammable coating layer, And the outer layer is made to be a nonflammable coating layer so that the lithium secondary battery can maintain safety in the risk of ignition or physical environment.

Accordingly, it is an object of the present invention to provide an outer casing for a lithium secondary battery which improves safety by preventing thermal shock of a lithium secondary battery due to various external environments.

Another object of the present invention is to provide a lithium ion secondary battery which can maintain the appearance of a battery constantly, including a case having the above-mentioned thermal stability.

The outer layer itself constituting the casing of the secondary battery may be formed of a nonflammable coating layer or a nonflammable coating layer may be formed on at least one surface of the outer layer as in the present invention to deteriorate battery performance from heat generated by overcharging or external ignition sources. It is possible to provide excellent flame retardancy without the need for a flame retardant. Further, the outer appearance of the battery can be kept constant by applying the outer surface of the battery to the non-combustible coating layer.

In order to accomplish the above object, a casing of a secondary battery according to the present invention includes a nonflammable coating layer.

A secondary battery according to another aspect of the present invention includes the outer casing.

Hereinafter, the present invention will be described in more detail.

The outer casing for a secondary battery of the present invention is intended to contain an electrolyte and an electrode assembly therein. In a typical outer casing formed by sequentially laminating an inner layer, a metal foil layer, and an outer layer from an inner surface in contact with an electrolyte, Itself is formed as a nonflammable coating layer, or a nonflammable coating layer is formed on at least one surface of the outer layer.

That is, the nonflammable coating layer according to the present invention is an outer layer or is separately contained on at least one side of the outer layer.

When the non-flammable coating layer of the present invention is separately applied to the outer layer, the non-flammable coating layer may be formed by applying a flame-retardant polymer. As the flame-retardant polymer, those selected from polyethylene, polypropylene, polyurethane, and fluorine-based polymers are used.

In this case, it is preferable that the polymer is thermally melted or dissolved in a suitable solvent. The thickness of the non-combustible coating layer is preferably several micro to 1 mm, but is not limited thereto.

When the nonflammable coating layer according to the present invention is an outer layer, it may be obtained by applying a dispersion in which a non-combustible material is dispersed to a solution of at least one polymer selected from the group consisting of a polymer forming the outer layer, a thermoplastic resin and a thermosetting resin. have.

The polymer forming the outer layer may be a polydimethylsiloxane (PDMS) blendable with a nonflammable material, but is not limited as long as it is blendable. Specific examples of the thermoplastic resin include at least one selected from the group consisting of polyethylene, polypropylene, polystyrene, polyester, polyamide, acrylic resin, vinyl chloride resin, vinyl acetate resin, ABS and celluloid resin, But is not limited thereto.

In addition, the thermosetting resin can be melted and mixed with a non-combustible material to form it as an outer layer. Specific examples of the thermosetting resin include, but are not limited to, at least one selected from the group consisting of a polyurethane, a phenol resin, a melamine resin, and an alkyd resin.

As the non-combustible material included in the polymer solution, a halogen-based flame retardant, a phosphorus-based flame retardant, and an inorganic compound flame retardant may be used, and in some cases, they may be used in the form of one or a mixture of two or more thereof.

The halogen-based flame retardant generally exhibits a flame retarding effect by substantially stabilizing the radicals generated on the gas phase. Examples of halogen-based flame retardants include tribromophenoxyethane, tetrabromobisphenol-A (TBBA), octabromophenyl ether (OBDPE), brominated epoxy, brominated polycarbonate oligomer, chlorinated paraffin, chlorinated polyethylene, Flame retardants and the like.

The phosphorus flame retardant generally produces a polymetaphosphoric acid by pyrolysis and forms a protective layer, or a carbon film formed by the dehydration action when polymetaphosphoric acid is produced blocks oxygen, thereby exhibiting a flame retarding effect. Examples of the phosphorus flame retardant include phosphates such as ammonium phosphates, phosphine oxides, phosphine oxide diols, phosphites, phosphonates, triaryl phosphates, phosphate, alkyldiaryl phosphate, trialkylphosphate, and resorcinol bisdiphenyl phosphate (RDP).

The inorganic compound flame retardant is generally decomposed by heat to release an incombustible gas such as water, carbon dioxide, sulfur dioxide, and hydrogen chloride to induce an endothermic reaction, thereby preventing the access of oxygen by diluting the flammable gas and cooling and pyrolysis The production of the product is reduced and the flame retarding effect is exhibited. Examples of such inorganic compound flame retardants include asbestos, aluminum hydroxide, magnesium hydroxide, antimony oxide, tin hydroxide, tin oxide, molybdenum oxide, zirconium compounds, borate salts and calcium salts.

In some cases, it may further include other additives for inducing a flame-retarding synergistic effect when mixed with the above-mentioned incombustible materials.

The content of the nonflammable material in the polymer solution is preferably 10 to 20% by volume based on the volume of the polymer solution.

The thickness of the nonflammable coating layer is not particularly limited as long as it does not affect the constitution of the battery. The nonflammable coating layer formed of a solution in which the nonflammable material is dispersed in the flame-retardant polymer layer or the polymer solution may be formed on at least one side of the casing or the casing, or may be formed of two or more layers .

It is preferable that the total thickness of the cross-section of the outer casing for the secondary battery of the present invention is several micro to 1 mm, and the thicknesses of the inner layer and the outer layer are preferably several tens microns and several micros to 1 mm, respectively.

The metal foil layer of the pouch exterior material has a proper thickness and prevents penetration of water vapor and gas from the outside to the inside, and prevents leakage of the electrolytic solution. As the metal foil layer, an alloy of iron (Fe), carbon (C), chromium (Cr) and manganese (Mn), an alloy of iron (Fe), carbon (C), chromium (Cr) and nickel (Al) or an equivalent thereof may be used, but the present invention is not limited thereto. However, when the metal foil layer is made of iron-containing material, the mechanical strength is strengthened, and when the metal foil layer is made of aluminum-containing material, flexibility is improved. Normally, an aluminum metal foil is preferably used.

The inner layer constituting the pouch exterior member may be a thermally adhesive layer such as a modified polypropylene such as casted polypropylene (CPP), a polypropylene-butylene-ethylene terpolymer, or the like. The inner layer is coated or laminated to the other surface of the metal foil layer to a thickness of about 30 to 40 mu m.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example  1: as a nonflammable coating layer Outer layer  At least one surface of which is coated with a flame-retardant polymer solution Manufacturing example .

An outer layer was formed by coating a polymer solution in which polyurethane was dissolved in an organic solvent to an aluminum foil having a thickness of 40 to 50 占 퐉 to a thickness of 500 占 퐉. Further, polypropylene was applied to the opposite surface of the aluminum foil on which the outer layer was formed to a thickness of 20 mu m to form an inner layer.

Further, a non-flammable coating layer was coated on at least one surface of the outer layer with a thickness of 100 탆 by blending polyurethane, which is a flame-retardant polymer, into PDMS. Further, a pouch-type outer cover material for a secondary battery was prepared by forming an additional non-flammable coating layer having a thickness of 500 mu m by blending an asbestos which is an inorganic flame retardant substance with PDMS on an upper portion of the flame-retardant polymer-made non-flammable coating layer.

Example 2: Example in which the outer layer is an incombustible coating layer

A dispersion liquid in which 1 g of polyimide as a noncombustible substance is added and dispersed in a polymer solution forming the outer layer is coated on the aluminum foil to a thickness of 10 탆 without applying a noncombustible coating layer on at least one side of the outer layer, And the inner layer and the metal foil layer were formed in the same manner as in Example 1, except that a pouch-type sheathing material for a secondary battery was manufactured.

Comparative Example

A pouch-type sheathing material according to Example 1, which does not include a separate nonflammable coating layer, was used as a comparative example of the present invention.

The chemical stability and heat resistance of ethylene carbonate / ethylmethyl carbonate / dimethyl carbonate (EC / EMC / DMC) electrolyte to the outer casing of the pouch of the secondary battery prepared in the above Examples and Comparative Examples were measured by a hot box method . As a result, it was confirmed that the pouch outer sheath according to the present invention was chemically safe and excellent in heat resistance.

Claims (16)

1. A jacket of a secondary battery comprising an inner layer, a metal foil layer and an outer layer, A non-combustible coating layer formed by applying a solution in which a non-combustible material is blended in a polymer solution that can be blended with a non-combustible material, on at least one side of the outer layer, Wherein the incombustible material is dispersed in an amount of 10 to 20 vol% based on the volume of the polymer solution. delete delete delete delete The exterior material of a secondary battery according to claim 1, wherein the polymer blendable with the incombustible material is polydimethylsiloxane (PDMS). delete delete delete The exterior material of a secondary battery according to claim 1, wherein the nonflammable material is at least one selected from the group consisting of a halogen-based flame retardant, a phosphorus-based flame retardant, and an inorganic compound flame retardant. The method of claim 10, wherein the halogen-based flame retardant is selected from the group consisting of tribromophenoxyethane, tetrabromobisphenol-A (TBBA), octabromodiphenyl ether (OBDPE), brominated epoxy, brominated polycarbonate oligomer, chlorinated paraffin, Polyethylene, and an alicyclic chlorine-based flame retardant. 11. The method of claim 10, wherein the phosphorus flame retardant is selected from the group consisting of phosphine oxide, phosphine oxide diols, phosphites, phosphonates, triaryl phosphates, alkyl Wherein at least one selected from the group consisting of alkyldiaryl phosphate, trialkyl phosphate, and resorcinol bisdiphenyl phosphate (RDP) is used. The method according to claim 10, wherein the inorganic compound flame retardant is at least one selected from the group consisting of asbestos, aluminum hydroxide, magnesium hydroxide, antimony oxide, tin hydroxide, tin oxide, molybdenum oxide, zirconium compound, borate, The exterior of the secondary battery. The exterior material of a secondary battery according to claim 1, wherein the nonflammable material is at least one flame retardant polymer selected from the group consisting of polyethylene, polypropylene, polyurethane, and fluorine-based polymers. The exterior material of a secondary battery according to claim 1, wherein the thickness of the nonflammable coating layer is from several microamperes to 1 mm. A secondary battery comprising the casing according to claim 1.