KR102194075B1 - Lithium pouch type battery - Google Patents

Abstract

An electrode assembly including a positive electrode, a negative electrode, and a separator, and an oriented polystyrene (OPS) film attached to an outer surface of the electrode assembly, wherein the separator comprises a porous substrate and a coating layer formed on at least one surface of the porous substrate Including, the coating layer is provided with a lithium pouch-type battery comprising a polymer, ceramic, or a combination thereof.

Description

Lithium pouch type battery {LITHIUM POUCH TYPE BATTERY}

It relates to a lithium pouch type battery.

Lithium pouch-type batteries, which are in the spotlight as a power source for portable small electronic devices in recent years, use organic electrolytes, and thus display a discharge voltage that is twice as high as that of batteries using an aqueous alkaline solution, resulting in a high energy density. .

Lithium pouch-type batteries are used in which an electrode assembly is housed in a case and an electrolyte is injected to seal it. The electrode assembly may be formed by interposing a separator between the positive electrode and the negative electrode and winding them in a jelly-roll form.

In the electrode assembly, a finishing material is used on the outer end surface of the electrode assembly in order to fix the finished portion, and the electrode assembly with the finishing material is accommodated in a case, and then the electrolyte is injected into the case and sealed.

Such a lithium pouch-type battery is weak against external shocks, and thus stability of the battery may be deteriorated.

One embodiment is to provide a lithium pouch-type battery that is strong against external impact and has excellent stability.

An exemplary embodiment includes an electrode assembly including an anode, a cathode, and a separator positioned between the anode and the cathode; And an oriented polystyrene (OPS) film attached to an outer surface of the electrode assembly, wherein the separator includes a porous substrate and a coating layer formed on at least one surface of the porous substrate, and the coating layer is a polymer, ceramic or It provides a lithium pouch type battery including a combination thereof.

The oriented polystyrene film may be attached in a form in which one surface of the electrode assembly is open.

The electrode assembly may have a jelly-roll shape in which the positive electrode, the separator, and the negative electrode are sequentially wound, and the separator may be wound once more than the positive electrode and the negative electrode.

The outer adhesion of the oriented polystyrene film may be stronger than the inner adhesion.

The adhesive strength of the oriented polystyrene film may be 0.5 to 8 kgf/cm ² .

The elongation rate of the oriented polystyrene film may be 10 to 400 kgf/cm ² .

The polymer may include polyvinylidene fluoride-based polymer, acrylic polymer, polymethyl methacrylate (PMMA), aramid resin, polyamide-imide resin, polyimide resin, or a combination thereof.

The polyvinylidene fluoride-based polymer may include polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer, or a combination thereof.

The ceramic may include Al ₂ O ₃ , MgO, TiO ₂ , Al(OH) ₃ , Mg(OH) ₂ , Ti(OH) ₄ or a combination thereof.

The thickness of the coating layer may be 0.1 to 6 μm.

The lithium pouch type battery includes: a pouch case accommodating the electrode assembly; And a polymer electrolyte injected into the pouch case.

The polymer electrolyte may include C1 to C10 alkyl propionate.

Details of other implementations are included in the detailed description below.

It is possible to implement a lithium pouch-type battery that is strong against external impact and has excellent stability.

1 is a schematic diagram showing a lithium pouch type battery according to an embodiment.
2 is a nonparametric survival plot of a free fall experiment of lithium pouch-type batteries according to Example 1 and Comparative Example 1. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

A lithium pouch-type battery according to an embodiment will be described with reference to FIG. 1.

1 is a schematic diagram showing a lithium pouch type battery according to an embodiment.

Referring to FIG. 1, a lithium pouch type battery 100 according to an embodiment includes an electrode assembly 10, a finishing material 15 attached to the outer surface of the electrode assembly 10, and the electrode assembly 10. It may include a pouch case 20 and an electrode tab 13 serving as an electrical path for guiding the current formed in the electrode assembly 10 to the outside. The two surfaces of the pouch case 20 overlap and seal the surfaces facing each other. In addition, a polymer electrolyte is injected into the pouch case 20 containing the electrode assembly 10.

The electrode assembly 10 includes an anode, a cathode facing the anode, and a separator disposed between the anode and the cathode. The separator may include a porous substrate and a coating layer formed on at least one surface of the porous substrate.

In addition, the electrode assembly 10 may have a jelly-roll shape in which the positive electrode, the separator, and the negative electrode are sequentially wound.

The finishing material 15 may be an oriented polystyrene (OPS) film. The oriented polystyrene film is a material that is easy to form due to its low melting temperature and melt viscosity during molding. When the oriented polystyrene film is attached to the outer surface of the electrode assembly, the jelly-roll shape is stably maintained so that the wound electrode assembly does not unwind as the oriented polystyrene film has adhesiveness when heat-pressed. I can. In addition, since the electrode assembly is in close contact with the pouch case 20, adhesion between them may be strengthened. Accordingly, the jelly-roll shape of the electrode assembly is stably maintained even with an external impact, and the fluidity of the electrode assembly in the pouch case 20 is not large.

When the shape of the jelly-roll of the electrode assembly is deformed or the fluidity of the electrode assembly in the pouch case is increased, an internal short circuit occurs in the battery, thereby deteriorating the performance of the battery. According to an embodiment, since the jelly-roll shape of the electrode assembly is stably maintained and the flow of the electrode assembly inside the pouch case is prevented even with an external impact, deterioration of battery performance can be prevented.

The oriented polystyrene film may have an outer adhesive force that is stronger than an inner adhesive force.

The adhesive strength of the oriented polystyrene film may be 0.5 to 8 kgf/cm ² , and specifically 0.5 to 5 kgf/cm ² . When it has an adhesive strength within the above range, excellent adhesion formed during heat press can be obtained.

The elongation of the oriented polystyrene film may be 10 to 400 kgf/cm ² , and specifically 50 to 200 kgf/cm ² . When it has an elongation within the above range, excellent adhesion formed during heat press can be obtained.

When the oriented polystyrene film is attached to the outer surface of the electrode assembly, one surface of the electrode assembly may be attached in an open form. Specifically, one surface of the electrode assembly, which corresponds to a gas room through which gas discharged from the pouch case is introduced during the degas process, may be attached in an open form. This is to secure a passage for discharging gas during the degas process.

The separator may include a porous substrate and a coating layer formed on at least one surface of the porous substrate.

The porous substrate may be a polyolefin resin. Examples of the polyolefin resin include polyethylene resins, polypropylene resins, or combinations thereof.

The coating layer may be a polymer, ceramic, or a combination thereof.

When the above-described finishing material, in particular, the oriented polystyrene film is heat-pressed, the coating layer also has adhesiveness, and accordingly, the jelly-roll shape can be stabilized so that the wound assembly is not released. As described above, according to one embodiment, due to the oriented polystyrene film attached to the outer surface of the electrode assembly and the separator coated with the coating layer on the surface of the porous substrate, the jelly-roll form of the electrode assembly is stably doubled. Will be maintained.

The electrode assembly has a jelly-roll shape in which the positive electrode, the separator, and the negative electrode are sequentially wound, and the separator may be wound once more than the positive electrode and the negative electrode. When the separator is wound once more, adhesiveness is additionally imparted to the portion wound once more due to the adhesion of the separator generated when the oriented polystyrene film is thermally pressed. Accordingly, the electrode assembly in which the separator is wound one more time may further enhance adhesion to the pouch case, thereby preventing the electrode assembly from flowing inside the pouch case. As described above, according to one embodiment, due to the form in which the oriented polystyrene film attached to the outer surface of the electrode assembly and the separator are wound once more, as well as stably maintaining the jelly-roll shape of the electrode assembly, It is possible to minimize the fluidity of the electrode assembly inside the pouch case.

In an environment such as overcharging a battery or leaving it at a high temperature, gas is generated as the pressure and temperature inside the battery increase, and by discharging such gas, expansion and explosion problems of the battery can be prevented. Accordingly, after attaching the finishing material to the outer surface of the electrode assembly, a degassing process is performed, and the inside of the pouch case must be inflated when degassing. To this end, when the finishing material is attached to the outer surface of the electrode assembly, the separator is wound once more mainly when winding the electrode assembly. In this case, when the separator according to one embodiment is used, the separator itself has adhesiveness, so it can serve as a finishing material. Accordingly, it is possible to prevent the electrode assembly from flowing inside the pouch case.

The polymer constituting the coating layer may be a polyvinylidene fluoride polymer, an acrylic polymer, polymethyl methacrylate (PMMA), an aramid resin, a polyamideimide resin, a polyimide resin, or a combination thereof.

Examples of the polyvinylidene fluoride-based polymer include polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer, or a combination thereof.

The ceramic may be Al ₂ O ₃ , MgO, TiO ₂ , Al(OH) ₃ , Mg(OH) ₂ , Ti(OH) _4, or a combination thereof.

The thickness of the coating layer may be 0.1 to 6 μm, and specifically 2 to 4 μm. When the coating layer has a thickness within the above range, the jelly-roll shape of the electrode assembly is maintained intact even with external impacts such as when the battery falls, and the adhesion of the electrode assembly within the pouch case can be prevented. I can.

The positive electrode constituting the electrode assembly includes a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material, a binder, and optionally a conductive material.

Al (aluminum) may be used as the current collector, but is not limited thereto.

As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (reitiated intercalation compound) may be used. Specifically, one or more of a complex oxide of cobalt, manganese, nickel, or a combination of metal and lithium may be used, and a specific example thereof may be a compound represented by any one of the following formulas:

Li _a A _1-b B _b D ₂ (where 0.90≦a≦1.8, and 0≦b≦0.5); Li _a E _1-b B _b O _2-c D _c (where 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05); LiE _2-b B _b O _4-c D _c (where 0≦b≦0.5, 0≦c≦0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1); Li _a NiG _b O ₂ (in the above formula, 0.90≦a≦1.8 and 0.001≦b≦0.1); Li _a CoG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a MnG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a Mn ₂ G _b O ₄ (In the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1.); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≦f≦2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≦f≦2); And LiFePO ₄ .

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or combinations thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y or a combination thereof; J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Of course, one having a coating layer on the surface of the compound may be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may include at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compound constituting these coating layers may be amorphous or crystalline. As a coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. The coating layer formation process is a method that does not adversely affect the physical properties of the positive electrode active material by using these elements in the compound (e.g., spray coating, dipping method, etc.), any coating method may be used. Since the content can be well understood by those in the field, detailed descriptions will be omitted.

The binder adheres the positive electrode active material particles well to each other and also serves to attach the positive electrode active material well to the current collector, and specific examples include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, Carboxylated polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber , Acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but are not limited thereto.

The conductive material is used to impart conductivity to the electrode, and in the battery constituted, any material can be used as long as it does not cause chemical change and is an electron conductive material, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like may be used, and conductive materials such as polyphenylene derivatives may be used alone or in combination of one or more.

The negative electrode constituting the electrode assembly includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector.

The negative electrode current collector may use a copper foil.

The negative active material layer includes a negative active material, a binder, and optionally a conductive material.

The negative active material includes a material capable of reversibly intercalating/deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating/deintercalating lithium ions, any carbon-based negative active material commonly used in lithium pouch-type batteries may be used as a carbon material, and a representative example thereof is crystalline carbon. , Amorphous carbon, or they may be used together. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low temperature calcined carbon). Alternatively, hard carbon, mesophase pitch carbide, and fired coke may be used.

As the lithium metal alloy, in the group consisting of lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn The alloy of the metal of choice can be used.

Materials capable of doping and undoping lithium include Si, SiO _x (0 <x <2), Si-C composites, Si-Y alloys (wherein Y is an alkali metal, alkaline earth metal, group 13 to group 16 element , Transition metal, rare earth element, and an element selected from the group consisting of a combination thereof, and not Si), Sn, SnO ₂ , Sn-C complex, Sn-Y (wherein Y is an alkali metal, alkaline earth metal, group 13 to It is an element selected from the group consisting of a group 16 element, a transition metal, a rare earth element, and a combination thereof, and not Sn), and the like, and at least one of these and SiO ₂ may be mixed and used. The element Y is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, It may be selected from the group consisting of Se, Te, Po, and combinations thereof.

The transition metal oxide may include vanadium oxide and lithium vanadium oxide.

The binder adheres well the negative electrode active material particles to each other and also plays a role in attaching the negative electrode active material to the current collector well, and representative examples thereof include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, polyvinyl chloride, carboxylation Polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic ray Tied styrene-butadiene rubber, epoxy resin, nylon, etc. may be used, but the present invention is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and in the battery constituted, any material can be used as long as it does not cause chemical change and is an electron conductive material, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen Carbon-based materials such as black and carbon fiber; Metal-based materials such as metal powder or metal fibers such as copper, nickel, aluminum, and silver; Conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material containing a mixture thereof may be used.

Each of the negative electrode and the positive electrode is prepared by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then applying the composition to a current collector.

Since such a method of manufacturing an electrode is widely known in the art, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like may be used, but is not limited thereto.

A polymer electrolyte is injected into the pouch case housing the electrode assembly.

The polymer electrolyte may include an alkyl propionate. The alkyl propionate has excellent compatibility with the polymer of the coating layer constituting the separator, so that the electrode assembly can be well impregnated. As a result, a lithium pouch-type battery having excellent overcharge characteristics can be implemented.

In the alkyl propionate, the alkyl may be a C1 to C10 alkyl, specifically, a C1 to C5 alkyl.

Specifically, the alkyl propionate may be one selected from methyl propionate, ethyl propionate, and combinations thereof. These have a low viscosity, so that the compatibility with the polymer of the coating layer constituting the separator is more excellent, and accordingly, the life characteristics during overcharging may be improved.

The alkyl propionate may be included in an amount of 10 to 70% by volume, specifically 20 to 70% by volume, and more specifically 40 to 60% by volume based on the total amount of the polymer electrolyte. When the alkyl propionate is added to the polymer electrolyte in the above content range, a lithium pouch-type battery having excellent overcharge characteristics can be implemented.

The electrolyte solution may be used by mixing a lithium salt and a non-aqueous organic solvent in addition to the alkyl propionate.

The lithium salt is dissolved in the non-aqueous organic solvent, acts as a source of lithium ions in the battery, enables basic operation of a lithium pouch-type battery, and promotes the movement of lithium ions between the positive electrode and the negative electrode. It is a substance that does.

Specifically, the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x and y are natural numbers), LiCl, LiI, LiB(C ₂ O ₄ ) ₂ (lithium bis(oxalato ) borate; LiBOB), and one selected from a combination thereof may be used.

The concentration of the lithium salt may be used within the range of about 0.1M to about 2.0M. When the concentration of the lithium salt is within the above range, since the electrolyte has an appropriate conductivity and viscosity, excellent electrolyte performance can be exhibited, and lithium ions can effectively move.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. The non-aqueous organic solvent may be one selected from a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, an aprotic solvent, and a combination thereof.

As the carbonate-based solvent, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate ( ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate , BC) and the like may be used.

Specifically, a chain carbonate compound and a cyclic carbonate compound may be mixed and used, and in this case, it may be prepared with a solvent having a low viscosity while increasing the dielectric constant. In this case, the cyclic carbonate compound and the chain carbonate compound may be mixed and used in a volume ratio of about 1:1 to 1:9.

The carbonate-based solvent and the alkyl propionate described above may be mixed in a volume ratio of 4:6 to 6:6. When mixed within the volume ratio range, a lithium pouch-type battery having excellent life characteristics during overcharging may be implemented.

Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalo Noractone (mevalonolactone), caprolactone (caprolactone) and the like may be used.

As the ether-based solvent, for example, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and the like may be used.

Cyclohexanone may be used as the ketone solvent.

Ethyl alcohol, isopropyl alcohol, and the like may be used as the alcohol-based solvent.

The non-aqueous organic solvent may be used alone or in combination of one or more, and the mixing ratio in the case of using one or more mixtures may be appropriately adjusted according to the desired battery performance.

The electrolyte may further contain an additive such as an overcharge inhibitor such as ethylene carbonate and pyrocarbonate.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are merely for illustrating or explaining the present invention in detail, and the present invention is not limited thereto.

In addition, information not described herein can be sufficiently technically inferred by those skilled in the art, and thus the description thereof will be omitted.

Example 1

LiCoO ₂ , polyvinylidene fluoride (PVdF) and carbon black were mixed in a weight ratio of 97:1.5:1.5, respectively, and dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode active material layer composition. The positive electrode active material layer composition was coated on an aluminum foil having a thickness of 12 μm, dried and rolled to prepare a positive electrode.

Graphite and styrene-butadiene rubber were mixed in a weight ratio of 98:2 and dispersed in water to prepare a negative active material layer composition. The negative active material layer composition was coated on a copper foil having a thickness of 8 µm, dried and rolled to prepare a negative electrode.

A polymer electrolyte was prepared by dissolving 1.1M LiPF ₆ in a mixed solution of ethylene carbonate (EC), propylene carbonate (PC), and ethyl propionate (EP) in a volume ratio of 3:1:6.

A coating layer composition containing polyvinylidene fluoride (PVdF) and N-methylpyrrolidone was prepared, and the coating layer composition was applied to one surface of a polyethylene substrate to form a coating layer to a thickness of 3 μm, thereby preparing a separator.

The prepared positive electrode, the separator, and the negative electrode were wound to prepare a jelly-roll type electrode assembly. The electrode assembly was formed by winding the separator once more than the positive electrode and the negative electrode. An oriented polystyrene film was attached to the outer surface of the electrode assembly, but one side was attached in an open form.

The electrode assembly finished with the oriented polystyrene film was accommodated in a pouch case, and the polymer electrolyte was injected and sealed to prepare a lithium pouch type battery.

Comparative Example 1

LiCoO ₂ , polyvinylidene fluoride (PVdF) and carbon black were mixed in a weight ratio of 97:1.5:1.5, respectively, and dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode active material layer composition. The positive electrode active material layer composition was coated on an aluminum foil having a thickness of 12 μm, dried and rolled to prepare a positive electrode.

Graphite and styrene-butadiene rubber were mixed in a weight ratio of 98:2 and dispersed in water to prepare a negative active material layer composition. The negative active material layer composition was coated on a copper foil having a thickness of 8 µm, dried and rolled to prepare a negative electrode.

A polymer electrolyte was prepared by dissolving 1.1M LiPF ₆ in a mixed solution of ethylene carbonate (EC), propylene carbonate (PC), and ethyl propionate (EP) in a volume ratio of 3:1:6.

A jelly-roll type electrode assembly was manufactured by winding the prepared positive and negative electrodes and a polyethylene separator. The electrode assembly is housed in a pouch case, and the polymer electrolyte is injected and sealed to produce a lithium pouch-type battery, and a protective circuit (PCM) and a secondary element are welded, and a stainless steel (SUS) case is used as an exterior package. ) Was produced.

Evaluation 1: Falling characteristics of lithium pouch type battery

After putting the lithium pouch-type battery packs of Example 1 and Comparative Example 1 in a case made of about 140 g of acetal, screwing the upper and lower cases, and performing random free fall 50 times at a height of 1 m. The number of times the heat generation occurred due to internal short was confirmed. The case was separated every 50 times to check the heat generation of the pack, and the number of free fall in which heat generation was confirmed is shown in Table 1 below.

Comparative Example 1 Example 1 Pack #1 50 times 500 times Pack #2 50 times 500 times Pack #3 100 times 500 times Pack #4 100 times 350 times Pack #5 250 times 500 times

As shown in Table 1, the lithium pouch-type battery of Example 1 including a separator including a coating layer and an OPS film according to one embodiment exhibits excellent dropping characteristics compared to Comparative Example 1, and is therefore resistant to external impacts and thus stability. It can be seen that this is excellent. In addition, nonparametric survival analysis of the lithium pouch-type batteries of Example 1 and Comparative Example 1 was measured, and the results are shown in FIG. 2.

2 is a nonparametric survival plot of a free fall experiment of lithium pouch-type batteries according to Example 1 and Comparative Example 1. FIG.

2, in the case of Comparative Example 1, the average number of free falls with heat generation was 110 times, and in the case of Example 1, the average number of free fall with heat generation was 470 times. It can be seen that the drop characteristics are greatly improved.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of the person skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of the present invention.

100: lithium pouch type battery
10: electrode assembly
20: pouch case
13: electrode tab
15: finishing material

Claims (8)

An electrode assembly including an anode, a cathode, and a separator positioned between the anode and the cathode;
A finishing material attached to the outer surface of the electrode assembly; And
It includes a pouch case accommodating the electrode assembly,
The finishing material is an oriented polystyrene (OPS) film,
The separator includes a porous substrate and a polymer coating layer formed on at least one surface of the porous substrate,
The polymer is polyvinylidene fluoride,
The electrode assembly has a jelly-roll shape in which the positive electrode, the separator, and the negative electrode are sequentially wound,
The separator is wound once more than the positive electrode and the negative electrode,
The oriented polystyrene film is attached in an open form on one side of the electrode assembly, corresponding to a gas room through which gas discharged from the pouch case is introduced during the degassing process.
Lithium pouch type battery.
delete The method of claim 1,
Lithium pouch-type battery in which the outer adhesion of the oriented polystyrene film is stronger than the inner adhesion.
The method of claim 1,
A lithium pouch-type battery having an adhesive strength of the oriented polystyrene film of 0.5 to 8 kgf/cm ² .
The method of claim 1,
The elongation of the oriented polystyrene film is 10 to 400 kgf / cm ² Lithium pouch type battery.
The method of claim 1,
The thickness of the coating layer is 0.1 to 6 ㎛ lithium pouch type battery.
The method of claim 1,
The lithium pouch type battery
Polymer electrolyte injected into the pouch case
Lithium pouch type battery further comprising a.
The method of claim 7,
The polymer electrolyte is a lithium pouch-type battery comprising a C1 to C10 alkyl propionate.

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