KR100882493B1 - Lithium Ion Polymer Battery Using Photosensitive Polymer As Separator - Google Patents

Abstract

The present invention relates to a lithium ion polymer battery using a photosensitive polymer as a separator, and more particularly, a photopolymerizable polymer is coated on an electrode active material layer (A) and subjected to selective polymerization after selective photopolymerization by light irradiation patterned into pores. By etching a portion to form a separator layer including pores, and coating an adhesive layer on the separator layer to provide a lithium ion polymer battery prepared by attaching a corresponding electrode active material layer (B), such a lithium ion polymer battery There is an effect of preventing an internal short circuit by preventing pinholes and / or tearing that may occur in a process of interposing a separator between the positive electrode and the negative electrode or assembling the separator.

Description

Lithium Ion Polymer Battery Using Photosensitive Polymer As Separator

1A and 1B are schematic diagrams of a process of manufacturing an electrode assembly of a lithium ion polymer battery according to one embodiment of the present invention.

The present invention relates to a lithium ion polymer battery using a photosensitive polymer as a separator, and more particularly, a photopolymerizable polymer is coated on an electrode active material layer (A) and subjected to selective polymerization after selective photopolymerization by light irradiation patterned into pores. It provides a lithium ion polymer battery prepared by etching a portion to form a separator layer including pores, coating an adhesive layer on the separator layer and then attaching a corresponding electrode active material layer (B).

As technology development and demand for mobile devices increase, the demand for batteries as energy sources is rapidly increasing, and accordingly, many studies on batteries that can meet various demands have been conducted. Among them, the demand for rechargeable batteries capable of charging and discharging is increasing, and recently, the ratio of high output and high capacity lithium secondary batteries to weight has increased significantly.

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.

In general, the porous polymer membrane is prepared by adding solid particles to a polyethylene / polypropylene (PE / PP) melt to form pores, applying a thin layer to a glass plate, drying, and then removing the solid particles. In addition, the PE / PP melt is applied by thin coating on a glass plate and then prepared by a method of partially rupturing.

When the polymer membrane is manufactured by the method using the solid particles, since the solid particles may be aggregated or large sized solid particles may be added, small pinholes may be formed in the polymer membrane that cannot be visually confirmed. It has a disadvantage. On the other hand, when manufacturing the polymer membrane by the stretching method, there is a disadvantage that too large holes may be generated or torn while stretching the polymer membrane. In addition, while the porous polymer separator is interposed between the positive electrode and the negative electrode, the polymer membrane in the form of a thin membrane is likely to be easily broken.

In the manufacturing process, a battery manufactured with a separator in which the above-mentioned defect occurs has an internal short circuit because the positive electrode and the negative electrode contact through the pinhole or the torn portion of the separator. Accordingly, there is a high demand for a lithium ion polymer battery including a polymer separator with a new structure capable of forming pores having a predetermined size in the polymer separator and interposing without damage between the positive electrode and the negative electrode.

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

After in-depth research and various experiments, the present inventors coated a photosensitive polymer with a positive electrode or a negative electrode as a separator in a lithium ion polymer battery to form pores by a lithography process, and then used the negative electrode or / and positive electrode as an adhesive. When manufacturing a lithium ion polymer battery by bonding, it was found that the internal short circuit can be prevented by preventing pinholes and tears that may occur during the process of assembling the separator or assembling the separator between the positive electrode and the negative electrode. The present invention has been completed based on this finding.

In order to achieve the above object, the lithium ion polymer battery according to the present invention is coated with a photosensitive polymer on the electrode active material layer (A), and the pores by developing unpolymerized sites after selective photopolymerization for light irradiation patterned in the shape of pores. It is formed by forming a separator layer comprising a, and after coating the adhesive layer on the separator layer to attach a corresponding electrode active material layer (B).

In the present invention, the electrode active material layer (A) may be a positive electrode active material layer or a negative electrode active material layer, or both a positive electrode and a negative electrode active material layer, and the corresponding electrode active material layer (B) may also be a negative electrode active material layer or a positive electrode active material layer, or a negative electrode and Both positive electrode active material layers may be used. That is, when the electrode active material layer (A) is a positive electrode active material layer, the corresponding electrode active material layer (B) becomes a negative electrode active material layer, when the electrode active material layer (A) is a negative electrode active material layer, the corresponding electrode active material layer (B) ) Becomes a positive electrode active material layer.

In some cases, the electrode active material layer (B) may be coated in the same manner as the separator layer is coated on the electrode active material layer (A).

The photosensitive polymer may be selectively used a photoresist used in the lithography process, the cross-linking is formed by the irradiation of light, and is left in the subsequent etching process, for example, remaining without being removed by the developer Type) A photoresist and a positive type photoresist that is removed by a developer as the chain is broken by the irradiation of light may be used.

In particular, a positive photorest that can selectively remove only the light irradiation site through a mask including a pore pattern can be preferably used. Examples of such phenolic novolak resins and diazos And PAC (Photo-Active-Compound) composed of compound derivatives. Such a PAC can be patterned by selectively irradiating G-rays (wavelength 436 nm) or I-rays (365 nm wavelength) of high pressure mercury lamp, for example. However, the chemically amplified resist KrF resist used in KrF laser exposure technology irradiating deep UV at 248 nm wavelength and the ArF resist used in ArF laser exposure technology at 193 nm wavelength may also be used. Of course it can.

In addition, the photosensitive polymer is preferably coated on the electrode active layer (A) to a thickness of 0.1 to 5 ㎛. This is because if the photosensitive polymer layer is too thin, a short circuit between the anode and the cathode may easily occur. If the photosensitive polymer layer is too thick, the thickness of the electrode assembly may be excessively thick and may hinder the movement of lithium ions.

The etching method includes a wet etching method using a chemical solution, a dry etching method using a plasma, an ion beam, and the like, and among them, a wet etching method using a developer is more preferable. As the developer, for example, a base aqueous solution such as a KOH aqueous solution can be used in the case of a positive photoresist, and an organic solvent such as acetone can be used in the case of a negative photoresist.

The adhesive layer is a fluorine-based polymer having excellent adhesion without lowering the mobility of lithium ions, and PVdF, which is widely used as a binder of electrode active materials, is particularly preferable, and is coated with a thickness of 1 to 5 μm.

In addition, the adhesive layer is attached to the photosensitive polymer layer by thermal fusion.

1A and 1B schematically show a series of processes for manufacturing an electrode assembly of a lithium ion polymer battery according to one embodiment of the present invention.

Referring to these drawings, in step (a), the positive electrode 10 having the positive electrode active material 12 coated on the positive electrode current collector 11 is manufactured.

In step (b), the photosensitive polymer layer 30, which is a positive photoresist, is coated on the positive electrode active material 12.

In step (c), when the mask 40 having the pattern of pores is positioned on the photosensitive polymer layer 30 and irradiated with the polymer layer 30 on the mask 40, the light is masked 40. Only through the pore portion of the polymer layer 30 can be irradiated.

Then, in step (d), the polymer layer 30 is selectively photolyzed only at the portion 31 to which light is irradiated.

In step (e), when the photolysis portion 31 of the polymer layer 30 is removed with a developer, a plurality of pores 35 are formed in the unirradiated portion 32.

In step (f), the adhesive layer 50 is coated on the polymer layer 30, and in step (g), the negative electrode 20 having the negative electrode active material 22 coated on the negative electrode current collector 21 is attached to the adhesive layer ( 50) Mount on.

Finally, in step (h), when the heat welding is performed, the positive electrode 10 and the negative electrode 20 are combined to produce an electrode assembly.

The positive electrode, the negative electrode, the electrolyte, and the like used in 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, if necessary, further adding a filler 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; Li _{1 + x} Mn _{2 - x} O ₄ (Where x is 0 to 0.33), lithium manganese oxides such as 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 coating and drying the 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, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like, 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

1-1. Manufacture of anode

LiCoO ₂ was used as the positive electrode active material, and 91% by weight of LiCoO ₂ , 6% by weight of Super-P (conductive agent), and 3% by weight of PVdF (binder) were added to N-methyl-2-pyrrolidone (NMP) as a solvent. After preparing the positive electrode mixture slurry, the positive electrode was prepared by coating, drying and pressing on an aluminum current collector.

1-2. Preparation of Cathode

As the negative electrode active material, artificial graphite was used, and 90% by weight of artificial graphite, 6% by weight of Super-P (conductive agent), and 4% 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 copper current collector.

1-3. Manufacture of batteries

As shown in the assembly process of Figure 1, a positive photoresist (PAC (Photo-Active-Compound) consisting of a phenolic novolak resin and a diazo compound derivative) as a separator component on the anode of 1-1 The layer was coated to a thickness of 1 μm, and the polymer layer was selectively polymerized by irradiating the polymer layer with light for 1 minute through a mask having a pattern of pores, and then using the developer solution of aqueous KOH solution for 2 minutes 30 After etching for a second, PVdF was applied on the polymer layer to a thickness of 1 μm, the cathode of 1-2 was mounted, and thermally fused to prepare an electrode assembly. A lithium ion polymer battery was prepared using an EC / EMC solution of 1M LiPF ₆ as an electrolyte solution in the electrode assembly.

Experimental Example 1

As a result of repeatedly performing charging and discharging on the lithium ion polymer battery prepared above under predetermined conditions and measuring current and voltage, it was confirmed that no problem occurs in comparison with a conventional battery.

In particular, since the separator is uniformly formed on the electrode by a lithography process, pinholes, tears, etc., which are often found in the separator of a conventional secondary battery, have not been found at all.

As described above, the lithium ion polymer battery according to the present invention has an effect of preventing an internal short circuit by preventing pinholes and / or tearing that may occur in a process of interposing a separator between an anode and a cathode or assembling the separator. have.

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 (10)

On the electrode active material layer (A), a photosensitive polymer, which is a positive photoresist, is coated with 0.1 to 5 μm, and after the selective photopolymerization by light irradiation patterned in the shape of pores, the unpolymerized portion is etched to form a separator layer including pores. And a lithium ion polymer battery formed by coating an adhesive layer of PVdF on the separator layer and then attaching a corresponding electrode active material layer (B). The lithium ion polymer battery according to claim 1, wherein the electrode active material layer (A) is a positive electrode active material layer, a negative electrode active material layer, or a positive electrode and a negative electrode active material layer. The lithium ion polymer battery according to claim 1, wherein a separator layer is coated on the electrode active material layer (B) by the same method as that described above. delete delete delete delete delete The lithium ion polymer battery of claim 1, wherein the adhesive layer is applied to a thickness of 1 to 5 μm. The lithium ion polymer battery according to claim 1, wherein the adhesive layer is attached by thermal fusion.

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