KR100895204B1 - Lithium Ion Polymer Battery of Improved Safety on Falling - Google Patents

Abstract

The present invention relates to a lithium ion polymer battery, comprising a electrode assembly having a separator attached between a positive electrode and a negative electrode, comprising: a separator constituting the electrode assembly on an outer surface of an outermost electrode of the electrode assembly; Provided is a battery composed of the same separator attached thereto.

As described above, in the lithium ion polymer battery according to the present invention, an internal short circuit caused by contact between a cathode lead frequently occurring during a drop and an anode located at an outermost part of the electrode assembly is configured to construct an electrode assembly without additional processing. By using a separation membrane, it is possible to further secure safety while maintaining battery performance.

Description

Lithium Ion Polymer Battery of Improved Safety on Falling}

1 is an exploded perspective view of a general structure of a conventional pouch-type polymer secondary battery;

FIG. 2 is a partially enlarged view of an upper portion of an inner case in which the positive electrode tabs are densely coupled and connected to the positive electrode lead in the secondary battery of FIG. 1;

3A to 3C are perspective views of an electrode assembly having a separator attached to an outermost electrode according to some embodiments of the present invention.

The present invention relates to a lithium ion polymer battery, comprising a electrode assembly having a separator attached between a positive electrode and a negative electrode, comprising: a separator constituting the electrode assembly on an outer surface of an outermost electrode of the electrode assembly; Provided is a battery composed of the same separator attached thereto.

Lithium secondary batteries are classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries according to the type of electrolyte used. Among them, lithium ion polymer batteries are manufactured by interposing a porous polymer separator between a positive electrode and a negative electrode, and then combining them and impregnating an electrolyte in the separator, thereby preventing leakage of electrolyte as much as possible. Has the advantage of very low risk of fire and explosion.

Such lithium ion polymer batteries are generally manufactured by embedding an electrode assembly including a positive electrode plate and a negative electrode plate coated with a positive electrode and a negative electrode active material, and a separator interposed therebetween in a pouch type case of an aluminum laminate sheet. Therefore, a lithium ion polymer battery is also called a pouch type battery.

1 schematically illustrates a general structure of a conventional pouch-type polymer secondary battery as an exploded perspective view.

Referring to FIG. 1, the pouch-type polymer secondary battery 100 may include an electrode assembly 300, electrode tabs 302 and 304 extending from the electrode assembly 300, and electrodes welded to the electrode tabs 302 and 304. It comprises a lead (400, 410), and a case 200 for receiving the electrode assembly.

The electrode assembly 300 is a structure in which a separator interposed between the anode and the cathode and insulates each other is stacked in the order of anode / separator / cathode. The electrode tabs 302, 304 extend from each pole plate of the electrode assembly 300, and the electrode leads 400, 410 may be connected to, for example, welded with a plurality of electrode tabs 302, 304 extending from each pole plate. Each is electrically connected to each other, and a part of the case 200 is exposed to the outside. The case 200 provides a space for accommodating the electrode assembly 300 and has a pouch shape. In the stacked electrode assembly 300 as shown in FIG. 1, a plurality of positive electrode tabs 310 and a plurality of negative electrode tabs 320 may be coupled together to the electrode leads 400 and 410. Is spaced apart from the electrode assembly 300.

FIG. 2 is a partially enlarged view of a top inside a case in which the positive electrode tabs are densely coupled in the secondary battery of FIG. 1 and connected to the positive electrode lead.

Referring to FIG. 2, a plurality of positive electrode tabs 302 extending from the positive electrode collector 310 of the electrode assembly 300 may be formed of, for example, a welded portion 322 integrally coupled by welding. It is connected to the anode lead 400 in the form. The positive lead 400 is sealed by the battery case 200 with the opposite end 402 to which the positive electrode tab fusion unit 322 is connected is exposed. Since the plurality of positive electrode tabs 302 are integrally coupled to form the fusion unit 322, the inner upper end of the battery case 200 is spaced apart from the upper end surface of the electrode assembly 300 by a predetermined distance, and the fusion unit ( The positive electrode tabs 302 of 322 are U-shaped.

Thus, when the battery falls to its top, i.e., the anode lead 400, or when a physical external force is applied to the top of the battery, the electrode assembly 300 is moved to the top of the inner surface of the case 200 or the top is crushed. As a result, the negative electrode current collector plate of the electrode assembly 300 may contact the positive electrode tab 302 or the positive electrode lead 400 to cause an internal short circuit. This internal short circuit is particularly caused when some positive electrode tabs under the fusion portion 322 are in contact with the negative electrode located at the outermost portion of the electrode assembly 300.

As described above, in order to prevent a short circuit caused by the contact of the anode lead and the outermost electrode of the electrode assembly which occurs most frequently, Japanese Laid-Open Patent Application 2003-257496 uses a back coat layer on the electrode of the outermost layer of the electrode assembly. Presenting techniques for shaping. However, the above-described technique is complicated by the process of manufacturing the electrode assembly and forming a back coat layer on the outermost layer electrode or a separate electrode having a back coat layer formed thereon, and thus operating the battery by forming a coating layer. It has disadvantages such as lowering efficiency.

Therefore, there is a high need for a technology that can fundamentally solve these problems.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

That is, an object of the present invention is to prevent the internal short circuit caused by the contact between the electrode lead that occurs frequently during the drop and the electrode located at the outermost part in the electrode assembly by a simple configuration, to further improve the safety while maintaining the performance of the battery It is to provide a lithium ion polymer battery that can be secured.

A lithium ion polymer battery according to the present invention for achieving the above object is a lithium ion polymer battery comprising an electrode assembly having a separator attached between the positive electrode and the negative electrode, the electrode assembly on the outer surface of the outermost electrode of the electrode assembly; It consists of attaching the same separator as the separator which comprises.

Therefore, the lithium ion polymer battery according to the present invention has an advantage of greatly improving the safety of the battery by a simple process of attaching a separator to the outer surface of the outermost electrode. Furthermore, since the separator attached to the outer surface of the outermost electrode is the same as the separator constituting the electrode assembly, there is also an advantage that it does not affect the operation of the battery at all.

The separator is preferably attached so as to apply an area of at least 30% or more from the top of the entire outer surface of the outermost electrode, so that contact is frequently made in particular adjacent to the electrode tab (or electrode lead) of the top surface of the outermost electrode. Only the parts that occur can be partially wrapped.

In some cases, the separator may be attached to its double-sided outermost electrodes while covering the top or bottom of the electrode assembly so that the outermost electrodes on both sides of the electrode assembly may be coated by one separator. In the case of covering the top of the electrode assembly, an opening is formed in a corresponding portion of the separator so that the electrode tab or the electrode lead may protrude. In another embodiment, one separator may be attached to its two-sided outermost electrodes with one side or both sides of the electrode assembly wrapped.

When the separator is attached to the outer surface of the outermost electrode, it is preferable that the adhesive layer is coated on one surface corresponding to the outer surface of the electrode in order to increase the adhesive force.

The coating layer is, for example, made of a fluorine-based polymer, it is preferable that the coating is so thin that does not cause a chemical change of the battery, and does not affect the thickness and appearance of the battery. These components may be the same as the material coated on the separator of the electrode assembly for bonding with the electrode in the manufacture of a lithium ion polymer battery, so that the preparation of the electrode assembly without separately preparing a separator attached to the outer surface of the outermost electrode The separator used, that is, the separator in which the electrode adhesion coating layer is formed can be applied as it is.

Such a separator is not particularly limited. The separator is an insulating thin film having high ion permeability and mechanical strength, and the pore diameter of the separator is generally 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. As such a separator, for example, olefin polymers such as chemical resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene are used.

The electrode constituting the outermost part of the electrode assembly may be a positive electrode or a negative electrode, and generally consists of a negative electrode for the balance of battery design between the positive electrode and the negative electrode, in particular for safety reasons.

3A to 3C are perspective views of an electrode assembly in which various types of separators are attached to the outermost electrode according to some embodiments of the present invention.

First, referring to FIG. 3A, the outermost electrodes of the stacked electrode assembly 300 in which the electrode terminals 500 and 510 are formed on the upper surface thereof, that is, the electrode assembly 300 and Two separators 600 and 610 are approximately equal or slightly larger than each other. Each of the separators 600 and 610 may be slightly smaller in size so as to be attached only to a portion adjacent to the electrode terminals 500 and 510. The attachment of the separators 600, 610 to the electrode assembly 300 is accomplished by thermally fusion bonding adhesive coating layers added to the surfaces thereof.

Referring to FIG. 3B, the separator 601 is attached to the double-sided outermost electrodes in a state in which the lower end of the electrode assembly 300 is wrapped as a unit.

In addition, referring to FIG. 3C, the separator 602 is attached to the double-sided outermost electrodes in a state in which one side of the electrode assembly 300 is wrapped as a unit as shown in FIG. 3B.

As described above, the separator may be attached to the outermost electrodes on both sides of the electrode assembly in various forms, and the shape of the separator may be included in the protection scope of the present invention based on the principles of the present invention.

The positive electrode, the negative electrode, the electrolyte, and the like of the lithium ion polymer secondary battery according to the present invention can be used as is known in the art, as will be described in detail below.

The positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive agent, and a binder onto a positive electrode current collector, followed by drying, and optionally, a filler may be further added to the mixture.

The positive electrode active material may be 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; Lithium manganese oxides such as Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein 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 (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like, but are not limited to these.

The positive electrode current collector is generally made to a thickness of 3 to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver or the like can be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The conductive agent is typically added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Such a conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive agent include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys 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 the active material and the conductive agent to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, 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 inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials, such as glass fiber and carbon fiber, are used.

The negative electrode is manufactured by applying and drying a negative electrode material on the negative electrode current collector, and if necessary, the components as described above may be further included.

The negative electrode current collector is generally made to a thickness of 3 to 500 ㎛. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver and the like on the surface, aluminum-cadmium alloy and the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode material may be, for example, carbon such as hardly 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': Al, B, P, Si, Group 1, 2, 3 of the periodic table) Metal composite oxides such as a group element, halogen, 0 <x ≦ 1, 1 ≦ y ≦ 3, 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; 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 metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The lithium salt-containing non-aqueous electrolyte consists of a solvent for a nonaqueous electrolyte and a lithium salt. As the solvent, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl Lactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolon, formamide, dimethylformamide, dioxolon, acetonitrile Nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxoron derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyroionate and ethyl propionate can be used.

The lithium salt is a good material to be dissolved in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , 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 carboxylic acid lithium, lithium tetraphenyl borate and imide have.

In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, etc. Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, etc. It may be. In some cases, in order to impart nonflammability, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics.

Hereinafter, the present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.

Example 1

80 to 90% by weight of the mixture of the manganese spinel-based compound and the Co-Ni-Mn-based compound, and 2 to 7% by weight of Super-P (conductor) and 2 to 7% by weight of PVdF (binder) were used as the active material. N-methyl-2-pyrrolidone) was added to prepare a positive electrode mixture slurry, and then coated, dried and pressed on an aluminum current collector to prepare a positive electrode.

85 to 95% by weight of artificial graphite, 0.5 to 5% by weight of Super-P (conductor), and 5 to 10% by weight of PVdF (binder) were added to NMP as a solvent to prepare a negative electrode mixture slurry. The negative electrode was prepared by coating, drying, and pressing on a current collector.

After sequentially stacking the separator interposed between the anode and the cathode prepared above, as shown in Figure 3a, a polyolefin-based separator of 9 cm wide and 17 cm long coated with a gel polymer on the outer surface of the negative electrode located at the outermost After further attaching and heat-sealed to prepare an electrode assembly. The electrode assembly was impregnated with 1M LiPF ₆ and EC / EMC-based electrolyte to prepare a lithium ion polymer battery.

Comparative Example 1

A battery was manufactured in the same manner as in Example 1, except that no separator was attached to the outer surface of the anode located at the outermost portion of the electrode assembly.

 Experimental Example 1

When each of the lithium ion polymer batteries manufactured in Example 1 and Comparative Example 1 was attached to a plastic sheet of 2 kg, and then fired at the tab site in a state where the tap direction was directed to the bottom at a height of 1 m The experiment was repeated to drop until. As a result of the experiment, the battery of Example 1 ignited as a ratio after 50 drop experiments, but the battery of Comparative Example 1 was confirmed that the ignition occurred in the tap region in the drop test within an average of 10 times.

As described above, the lithium ion polymer battery according to the present invention is a separator for constituting the electrode assembly without an additional step of the internal short circuit caused by the contact between the anode lead that occurs frequently during the drop and the cathode located at the outermost portion of the electrode assembly. By preventing the use thereof, there is an effect of further securing the safety while maintaining the performance of the battery.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (8)

A lithium ion polymer battery comprising an electrode assembly having a separator attached between a positive electrode and a negative electrode, wherein a separator similar to the separator constituting the electrode assembly is attached to an outer surface of the outermost electrode of the electrode assembly, and the separator is attached thereto. The adhesive layer of the coated fluorine-based polymer is directly heat-sealed to the outer surface of the outermost electrode, the battery, characterized in that attached to partially apply the top surface of the outermost electrode adjacent to the electrode tab (or electrode lead). delete delete The battery as claimed in claim 1, wherein the separator is attached to double-sided outermost electrodes in a state in which an upper end or a lower end of the electrode assembly is wrapped as a unit. The battery of claim 1, wherein the separator is attached to double-sided outermost electrodes in a state in which one side of the electrode assembly is wrapped as a unit. The battery of claim 1, wherein the outermost electrode is a negative electrode. delete delete

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