JP2014044865A - Lithium polymer secondary battery requiring no heat treatment cure and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium polymer secondary battery requiring no heat treatment curing and a method for manufacturing the lithium polymer secondary battery.SOLUTION: There are provided: a lithium polymer secondary battery which includes a positive electrode, a negative electrode and an ion conductive polymer electrolyte layer while the ion conductive polymer electrolyte layer comprises an ion conductive polymer electrolyte composition cured by irradiation with X-rays; and a method for manufacturing the lithium polymer secondary battery.

Description

  The present invention relates to a lithium polymer secondary battery that does not require heat treatment curing and a method for producing the same. More specifically, the present invention relates to a lithium polymer secondary battery having a lithium ion conductive polymer electrolytic layer produced by irradiating X-rays and a method for producing the same.

  Lithium secondary batteries have a very high theoretical energy density compared to other batteries, can be reduced in size and weight, can be reduced in thickness, have a high degree of freedom in shape selection, and have high safety. For this reason, it has attracted attention as a power source for mobile devices, and has been actively researched and developed as a power source for portable electronic devices. However, along with higher performance of portable electronic devices, further reductions in weight and thickness have been demanded, and in devices such as mobile phones, reliability and safety for a large number of repeated charge / discharge cycles have been demanded.

  Until then, in lithium secondary batteries, an electrolyte solution in which a lithium salt was dissolved in an organic solvent was used as the electrolyte between the positive electrode and the negative electrode. Therefore, in order to maintain reliability against liquid leakage, etc., an iron or aluminum can was used. Used as an exterior material. Therefore, the weight and thickness of the lithium secondary battery are limited to the weight and thickness of the metal can which is the exterior material.

  Currently, lithium polymer secondary batteries that do not use liquids as electrolytes are being developed and put into practical use. For lithium polymer secondary batteries, batteries that use lithium ion conductive polymers or lithium ion conductive gels as electrolytes are manufactured. ing. Since this type of battery has a solid electrolyte, it is easy to seal the battery, and it is possible to use a very light and thin material such as an aluminum laminate film for the exterior material, further reducing the weight and thickness of the battery. Is becoming possible.

  The lithium ion conductive polymer or the lithium ion conductive gel is often obtained by crosslinking by adding a lithium salt and optionally an organic solvent to a polymerizable monomer. As a crosslinking method, for example, the electrolyte solution is gelled by heating to form a positive electrode and a negative electrode (Patent Document 1), a combination of a thermal polymerization initiator and a polymerizable compound that are likely to undergo a thermal polymerization reaction. Thus, a method for obtaining an excellent polymer solid electrolyte gel (Patent Document 2) has been proposed. Furthermore, by using an actinic ray polymerization composition containing an actinic ray polymerization initiator, a photopolymerization method is obtained in which the polymerization is good and the polymerization proceeds completely even with a small amount of the initiator to obtain a polymerization composition (Patent Document 3). ), Or a lithium polymer secondary battery using a lithium ion conductive polymer gel between the positive electrode and the negative electrode, at least one polymerizable monomer and a lithium salt, a non-aqueous solvent, an initiator that initiates a polymerization reaction by ultraviolet irradiation. In the manufacturing method using the contained precursor solution, the battery characteristics and productivity of the lithium polymer secondary battery are improved by controlling the concentration of the photopolymerization initiator and the ultraviolet illuminance (Patent Document 4). ing. In addition, a method of forming electrodes and electrolytes with ionizing radiation such as an electron beam has been proposed (Patent Document 5).

Japanese Patent Laid-Open No. 11-219725 Japanese Patent Laid-Open No. 11-147989 JP-A-10-204109 JP 2003-92140 A Japanese Patent Application Laid-Open No. 5-290885

  Conventionally, as a method of curing a monomer-containing electrolyte solution impregnated in the positive electrode, negative electrode, and separator of a polymer secondary battery, a thermal curing method in which the electrolyte solution is polymerized by a thermopolymerization reaction of a monomer that is usually heated to 130 ° C. is lithium. Has been adopted in the manufacture of batteries. That is, in the conventional method, in order to cure the electrolytic solution containing the monomer or oligomer, not only uniform heating and accurate heating management are required, but also the insulation layer (separator) between the positive electrode and the negative electrode shrinks with curing. It often happens that a short circuit accident occurs because the insulation between the poles cannot be maintained. Also, in order to improve battery characteristics, attempts have been made to add flame retardants, oxidation-resistant agents, etc., but it has been difficult to use substances having a low boiling point as these additives in heat treatment at high temperatures. It was. In addition, it is uneconomical to carry out the curing process at a high heat treatment temperature, considering the equipment cost and energy cost, so if the treatment temperature is lowered, the heat treatment will take a long time and the monomer in the electrolyte will be polymerized. It had problems such as inevitable influence. Furthermore, since the shape and structure of the battery are affected to uniformly heat the battery to a predetermined temperature, it is difficult to freely process or deform the shape and structure of the battery. However, batteries once manufactured by heat treatment cannot be stored for a long period of time.

  The object of the present invention is to solve many problems associated with curing by heat treatment in the conventional method by curing reaction at room temperature. An object of the present invention is to provide a lithium polymer secondary battery that does not require heat treatment and a method for producing the same.

The present inventor has conducted intensive research and development with the clue that the problems of the conventional method can be solved by a curing reaction at room temperature, and thereby the ionic conductivity by short-time treatment at room temperature using X-rays. The present inventors have succeeded in polymerizing a polymer electrolyte composition (electrolytic solution), and have been able to eliminate many problems associated with curing by heat treatment so far.
The present invention includes the following lithium polymer secondary batteries (1) to (5) and lithium ion secondary batteries (6) to (10).
(1) A lithium polymer secondary battery having a positive electrode, a negative electrode, and an ion conductive polymer electrolyte layer, wherein the ion conductive polymer electrolyte layer is made of an ion conductive polymer electrolyte composition cured by X-ray irradiation. Polymer secondary battery.
(2) The ion conductive polymer electrolyte composition is selected from acrylic acid monomers having an unsaturated double bond obtained by esterifying a terminal hydroxyl group of an ester of acrylic acid with a polyhydric alcohol or a polyether polyol with acrylic acid. The lithium polymer secondary battery according to the above (1), which contains a monomer.
(3) The above (2), wherein the polyhydric alcohol or polyether polyol is one or more selected from ethylene glycol, propylene glycol, butylene glycol, trimethylolpropane, pentaerythritol, and polyethers derived therefrom. The lithium ion secondary battery described in 1.
(4) The lithium polymer secondary battery according to any one of (1) to (3), wherein the ion conductive polymer electrolyte composition includes an additive having a boiling point of 130 ° C. or lower.
(5) The lithium polymer secondary battery according to any one of (1) to (4), wherein the X-ray irradiation is an irradiation time of 30 seconds to 5 minutes.

(6) In the method for producing a lithium polymer secondary battery having a positive electrode, a negative electrode, and an ion conductive polymer electrolyte layer, the ion conductive polymer electrolyte layer is formed by irradiating and curing the ion conductive polymer electrolyte composition with X-rays. A method for producing a lithium polymer secondary battery, comprising: forming a lithium polymer secondary battery.
(7) A monomer in which the ion conductive polymer electrolyte composition is selected from acrylic acid-based monomers having an unsaturated double bond obtained by esterifying the terminal hydroxyl group of acrylic acid polyhydric alcohol ester or polyether polyol with acrylic acid The manufacturing method of the lithium polymer secondary battery as described in said (6) containing this.
(8) The above (7), wherein the polyhydric alcohol or polyether polyol is one or more selected from ethylene glycol, propylene glycol, butylene glycol, trimethylolpropane, pentaerythritol, and polyethers derived therefrom. The manufacturing method of the lithium ion secondary battery as described in 2 ..
(9) The method for producing a lithium polymer secondary battery according to any one of (6) to (8), wherein the ion conductive polymer electrolyte composition contains an additive having a boiling point of 130 ° C. or lower.
(10) The method for producing a lithium polymer secondary battery according to any one of (6) to (9), wherein X-rays are irradiated for 30 seconds to 5 minutes.

The present invention eliminates many problems associated with curing by conventional heat treatment by polymerizing an ion conductive polymer electrolyte composition (electrolyte) by short-time treatment at room temperature using X-rays. Thus, a lithium polymer secondary battery that does not require heat treatment curing can be provided.
The present invention produces the following effects by adopting a curing reaction by X-ray irradiation of an ion conductive polymer polymer electrolyte composition in the production of a lithium polymer secondary battery.
(1) The electrolytic solution that does not require a heating step can be cured.
(2) A low-boiling point substance can be used as an additive, and the selection range is widened, so that battery performance and safety can be improved.
(3) Since a highly safe battery is manufactured because no heat treatment is required, electronic elements such as mechanical elements and sensor actuators are integrated on a single silicon substrate glass substrate or organic material. It has become possible to provide devices as MEMS micro batteries and batteries that can be widely used in the medical field.
(4) The manufacturing cost is reduced and the safety of the battery is improved.
(5) Since it can be processed into various shapes, for example, it has become possible to store the battery in a space that has been considered impossible to store.

A battery element A is shown in which a positive electrode sheet and a negative electrode sheet are laminated with a polyethylene microporous film in between, and a positive lead and a negative lead are attached to the tab portions of the positive electrode sheet and the negative electrode sheet, respectively. Battery element B is shown in which battery element A is sandwiched between aluminum laminates, a polymer electrolyte solution is added, a positive electrode sheet active material layer, a negative electrode sheet active material layer, and a separator are impregnated with the polymer electrolyte solution and vacuum sealed.

The present invention is characterized in that, in the production of a lithium polymer secondary battery, the ion conductive polymer electrolyte composition is cured by irradiation with X-rays. Curing of polymer electrolyte compositions that can be easily applied to, for example, cylindrical shapes or complicatedly curved shapes, without the heat treatment process that tends to cause Provide technology. Furthermore, according to the present invention, a battery that can be stored for a long period of time can be provided.
The inventors have intensively studied to overcome the above-described problems of the prior art, and as a result, in a lithium polymer secondary battery using a lithium ion conductive polymer gel between the positive electrode and the negative electrode, at least one kind of X-ray polymerization. Ion conductive polymer electrolyte composition (precursor solution) containing a conductive monomer, lithium salt, and non-aqueous solvent is impregnated into the positive electrode, negative electrode, or substrate, and cured by irradiating X-rays for 30 seconds to 5 minutes for a short time. The present inventors have found a lithium polymer secondary battery using the electrode layer or polymer electrolyte layer thus obtained and a method for producing the same.

  In the present invention, in particular, in a secondary battery using an ion conductive polymer electrolyte layer between a positive electrode and a negative electrode, it is possible to obtain a polymer electrolyte layer having the shape stability required in the process by short-time irradiation with X-rays. It becomes. Since the polymer electrolyte composition can be cured in a short time by X-ray in this way, the productivity is improved and the curing at room temperature is possible, so the temperature rise of the polymer electrolyte composition solution is suppressed. In addition, volatilization of solvents and the like, and alteration of monomers and additives can be suppressed. As the monomer in the composition solution, it is preferable to use a monomer that can be crosslinked by X irradiation within 5 minutes.

As a typical example of the lithium polymer secondary battery in the present invention, the positive electrode or the positive electrode layer and the current collector, and the negative electrode or the negative electrode layer and the current collector are bonded to the external electrode, respectively, and the polymer electrolyte layer is interposed therebetween. It is configured with intervening. Examples of the shape include a cylindrical shape, a button shape, a square shape, and a sheet shape, but are not particularly limited thereto. Examples of the exterior material include metals and aluminum laminated resin films. When a sheet-like battery is produced using an aluminum laminated resin film, the aluminum laminated resin film is sealed by thermal fusion or thermocompression bonding.
Next, the lithium polymer secondary battery will be described in more detail.

[Components of lithium secondary battery]
A lithium polymer secondary battery targeted by the present invention includes, for example, a negative electrode containing a carbon material as a negative electrode active material, a positive electrode, a nonaqueous electrolytic solution, and a polymer electrolyte layer as main components. However, it is not particularly limited to those components, and may be configured by combining already known components. Below, a general aspect is shown as an example.

[Negative electrode]
[graphite]
It is formed by mixing a negative electrode active material with a conductive agent and a binder. Negative electrode active materials include lithium alloys such as metallic lithium and lithium aluminum, and materials that can insert and desorb lithium ions, such as conductive polymers such as polyacetylene, polythiophene, and polyparaphenylene, pyrolytic carbon, and presence of catalysts. Under the gas phase, pyrolyzed carbon, carbon fired from pitch, coke, tar, etc., carbon obtained by firing polymers such as cellulose, phenol resin, graphite such as natural graphite, artificial graphite, expanded graphite A material, a substance such as WO ₂ or MoO ₂ capable of inserting / eliminating lithium ions, or a complex thereof can be used.
Since the graphite material has a high true density and excellent conductivity, it has an advantage that a lithium secondary battery having a large capacity (high energy density) and good power characteristics can be constituted. Various types of carbon materials are used, and artificial graphite can be produced by, for example, heat-treating graphitizable carbon at a high temperature of 2800 ° C. or higher. As graphitizable carbon, tar pitch generally obtained from petroleum or coal is used as a raw material, and examples thereof include coke, MCMB, mesophase pitch carbon fiber, and pyrolytic vapor grown carbon fiber. Moreover, organic compound baked bodies, such as a phenol resin, can also be used.

  Also, non-graphitizable carbon called so-called hard carbon is used. This is a carbon material having an almost amorphous structure typified by glassy carbon. Generally, it is a material obtained by carbonizing a thermosetting resin. Non-graphitizable carbon has the advantages of high safety and relatively low cost. It is desirable to use as. As described above, carbon materials that can be used as the negative electrode active material include graphite materials such as natural graphite, spherical or fibrous artificial graphite, non-graphitizable carbon materials, and organic compound fired bodies such as phenol resins. And powdery bodies of graphitizable carbon materials such as coke. These carbon materials have respective advantages, and may be selected according to the characteristics of the lithium secondary battery to be manufactured.

An example of a method for producing a negative electrode used in the nonaqueous electrolyte secondary battery of the present invention will be described below. First, flaky natural graphite as a negative electrode active material and a styrene-butadiene rubber (SBR) dispersion as a binder (for example, having a solid content of 48%) are thickened in water as an aqueous solvent. A negative electrode active material slurry is prepared by adding carboxymethylcellulose (CMC) as an agent. Next, the obtained negative electrode active material slurry was applied to both surfaces of a negative electrode current collector made of copper foil (for example, having a thickness of 10 μm) so that the mass after drying was 200 g / m ^2. Layers are formed on both sides of the negative electrode current collector. Thereafter, after drying to remove moisture, the film is compressed by a roll press until the filling density of the negative electrode active material becomes 1.7 g / cm ³ . Then, it cut | disconnects so that it may fit in a battery width, and it vacuum-drys at 110 degreeC for 2 hours, and obtains a negative electrode.

  As the binder, a copolymer having a butadiene group can be preferably used. Examples of the copolymer having a butadiene group include styrene-butadiene rubber (SBR), carboxy-modified styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and acrylate-butadiene rubber. Moreover, the copolymer of a sodium acrylate, a propylene, and a C2-C8 olefin, the copolymer of (meth) acrylic acid and (meth) acrylic-acid alkylester, etc. can be used.

  Furthermore, a water-soluble thickener for improving the binding property of the water-soluble polymer binder is added. As the water-soluble thickener, a cellulose compound such as carboxymethylcellulose-alkali metal salt, hydroxypropylmethylcellulose-alkali metal salt, or methylcellulose-alkali metal salt can be used. In the alkali metal salt, Na, K, or Li can be used as the alkali metal. When the cellulose compound to which the alkali metal salt is added is used, the cellulose compound is used alone. Causes a decrease in electron conduction path and ion conduction path because water-soluble polymer binder and cellulosic compound are all non-conductors, eventually increasing the internal resistance of the battery, resulting in a high rate of battery There is a problem that causes deterioration of discharge characteristics, but this can be prevented.

  Polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, polymethacrylic acid, polyethylene oxide, polyacrylamide, poly-N-isopropylacrylamide, poly-N, N-dimethylacrylamide, polyethyleneimine, polyoxyethylene, poly (2- Methoxyethoxyethylene), poly (3-morpholinylethylene), polyvinyl sulfonic acid, polyvinylidene fluoride fluoride, amylose, and the like can also be used as thickeners.

The negative electrode is prepared by mixing a binder in these carbon material powders, applying a paste-like negative electrode mixture onto the surface of a current collector made of a metal foil such as copper, and then drying it. In response, the density of the negative electrode mixture is increased by a press or the like to form and manufacture a sheet.
The mixing ratio of the rubber-based polymer and the cellulose compound is 0.01 to 20 parts by mass of a copolymer having a butadiene group and 0.01 to 20 parts by mass of a cellulose compound with respect to 100 parts by mass of carbon. It is preferable. If the blending ratio of the copolymer having a butadiene group is less than this lower limit value, the flexibility of the negative electrode mixture may be lowered, and the cycle characteristics may be lowered. On the other hand, when the blending ratio of the copolymer having a butadiene group exceeds the upper limit value, the lithium insertion / extraction reaction may be inhibited, and the heavy load characteristics may be deteriorated. Moreover, the same tendency is seen also about a cellulose compound. In addition, the composition of the carbon, copolymer having a butadiene group and the cellulosic polymer are within this range, thereby improving rate characteristics and cycle characteristics, and maintaining high safety even when the energy density is 400 Wh / L or more. It can be a battery.

[Positive electrode]
Various materials can be used for the positive electrode active material. In general, composite oxides of Li and transition metals such as Co, Mn, Ni, Mo, V, Cr, Fe, Cu, and Ti can be used, but layered rock salt structure lithium cobalt composite oxide, layered rock salt structure It is preferable to use lithium nickel composite oxide, spinel structure lithium manganese composite oxide, or the like. It is also possible to use those obtained by substituting a part of the Li site or Co, Ni, or Mn site with another transition metal element, alkali metal element, alkaline earth element or the like. Transition metal chalcogenides; vanadium oxide and its Li compound; niobium oxide and its Li compound; conjugated polymer using organic conductive material; chevrel phase compound; activated carbon, activated carbon fiber, etc. It is also possible.

  The positive electrode is made by mixing a conductive material and a binder with a powder of a substance that can be a positive electrode active material, and adding a solvent to form a paste-like positive electrode mixture. It can be made into a sheet-like material formed by applying and drying the material and compressing it to increase the electrode density as necessary. The conductive material is for ensuring the electrical conductivity of the positive electrode, and a material obtained by mixing one or more carbon material powders such as carbon black, acetylene black, and graphite can be used. As in the case of the negative electrode, the binder may be a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluorine rubber, or a thermoplastic resin such as polypropylene or polyethylene. As a solvent for dispersing these active material, conductive material, and binder, an organic solvent such as N-methyl-2-pyrrolidone can be used as in the case of the negative electrode.

[Non-aqueous electrolyte]
The nonaqueous electrolytic solution is obtained by dissolving a lithium salt as an electrolyte in an organic solvent. The lithium salt is dissociated by dissolving in an organic solvent, and becomes lithium ions and exists in the electrolytic solution. Examples of the lithium salt that can be used include LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) _{2 and the} like. These lithium salts may be used alone, or two or more of these may be used in combination. The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 1.5 mol / L.

As the organic solvent for dissolving the lithium salt, an aprotic non-aqueous solvent is used. For example, cyclic carbonates such as propylene carbonate, ethylene carbonate, and butylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate; and lactones such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone. And cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, ethers such as dioxolane, diethyl ether, dimethoxyethane, diethoxyethane, and methoxyethoxyethane, dimethyl sulfoxide, sulfolane, methyl sulfolane, acetonitrile, methyl formate, and methyl acetate , Esters such as ethyl acetate, glymes such as methyl diglyme and ethyl diglyme, ethylene glycol, methyl cellosolve, Alcohols such as lysine, nitriles such as acetonitrile, propionitrile, methoxyacetonitrile, 3-methoxypropionitrile, N-methylformamide, N-ethylformamide, N, N-dimethylformamide, N, N-diethyl Examples thereof include amides such as formamide, N-methylacetamide, N-ethylacetamide, N, N-dimethylacetamide, and N-methylpyrrolidone, and phosphate esters such as trimethyl phosphate and triethyl phosphate. These solvents may be used alone or in combination of two or more.
If the amount of the polymerizable monomer contained in the lithium ion conductive polymer gel containing these non-aqueous solvents is too small, solidification is difficult, and if it is too large, lithium ion conductivity is inhibited. 50 is preferred.

[Separator]
In addition to serving as an insulator placed between the positive electrode and the negative electrode, the separator greatly contributes to retention of the electrolyte. Usually, a porous body such as polypropylene, polyethylene, a mixed cloth of both, or a glass filter is generally used.

[Polymer electrolyte composition]
In the polymer electrolyte composition, the ionic conductive polymer electrolyte composition is an acrylic acid-based polymer having an unsaturated double bond in which an ester of acrylic acid with a polyhydric alcohol or a terminal hydroxyl group of a polyether polyol is esterified with acrylic acid. Contains a monomer selected from monomers. The time when this monomer is polymerized may be after the battery is assembled. These monomers having an unsaturated double bond can be polymerized by irradiation with X-rays, but a polymerization initiator may be added to effectively advance the reaction.
As the polyhydric alcohol or polyether polyol, ethylene glycol, propylene glycol, butylene glycol, trimethylolpropane, pentaerythritol, and polyethers derived therefrom are used. For example, examples of polyethers derived from ethylene glycol include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether.

  Examples of the monomer having an unsaturated double bond include, for example, an ester of acrylic acid with a polyhydric alcohol or an acrylic acid type having an unsaturated double bond obtained by esterifying the terminal hydroxyl group of a polyether polyol with acrylic acid or methacrylic acid. Monomers such as polyalkylene glycol polyacrylates such as polyethylene glycol acrylate, glycidyl acrylate, allyl acrylate, polyethylene glycol polyacrylate, polypropylene glycol polyacrylate, trimethylolpropane polyacrylate, pentaerythritol alkoxylate polyacrylate, dipentaerythritol polyacrylate poly Polyesters such as undecylate and dipentaerythritol hexaacrylate and acrylic acid It can be used Le acids.

  Moreover, as said component, it is not limited to a monomer, an oligomer, or a polymer, If it can harden | cure, it can be used. Further, the curing is not limited to one type of monomer, oligomer or polymer, and a plurality of types of gelling components can be mixed as required. These monomers are preferably 95 to 30% by mass of the polymer forming the gel electrolyte, more preferably 90 to 40% by mass, and further preferably 60 to 45% by mass. In addition, a bifunctional acrylate monomer or a methacrylate monomer, a trifunctional or higher functional acrylate monomer or a methacrylate monomer may be used alone or in combination of two or more.

[Initiator]
The polymer electrolyte composition solution does not necessarily require a polymerization initiator, but phosphine oxide, acetophenone, benzophenone, α-hydroxyketone, Michlerketone, benzyl, benzoin, benzoin ether, benzyldimethyl Examples include ketals. From the above, one kind or a combination of two or more kinds may be used.
[Additive]
The ion conductive polymer electrolytic composition can be mixed with an additive having a boiling point of 130 ° C. or lower to improve battery performance. Examples of such additives include phosphazene compounds, fluoroethers, dimethyl carbonate, diethyl carbonate, and methyl ethyl ketone.

[Curing test by electrolyte X-ray]
The polymerization state of the monomer by X-ray irradiation was investigated. A polymer electrolyte composition comprising 7.1% by weight of dipentaerythritol hexaacrylate (DPEHA), 35.5% by weight of propylene carbonate, 38.9% by weight of ethylene carbonate, and 18.5% by weight of LiPF6 is output. The polymerization state of the polymer electrolyte composition was observed by irradiation with X-rays of 60 kv and 66 mA. The X-ray irradiation time was 60 seconds, 120 seconds, and 250 seconds, and the content of Trigonox 23C-70 as a polymerization initiator was 0.2% by weight with respect to the polymer electrolyte composition. Various types of curing tests were performed. The results are shown in Table 1. When the cured gel was visually observed, the gel was cured without any problems under all conditions irradiated with X-rays, and there was no change in the cured state depending on the presence or absence of the polymerization initiator and the polymerization conditions of the irradiation time.

[Manufacture of batteries]
By using the polymer electrolyte composition according to the present invention, a lithium polymer secondary battery can be manufactured according to a manufacturing method well known to those skilled in the art. In the production of the lithium polymer secondary battery of the present invention, a battery assembly in which a negative electrode and a positive electrode are opposed to each other to form an electrode body, and the electrode body is impregnated with a nonaqueous electrolytic solution and a polymer electrolyte composition is assembled. It is manufactured by a known method consisting of an attaching step. For example, a sheet-like positive electrode and a negative electrode are made to face each other to form an electrode body, and a separator serving to hold the polymer electrolyte composition by separating the positive electrode and the negative electrode is sandwiched between the positive electrode and the negative electrode. For this separator, a thin microporous film such as polyethylene or polypropylene can be used.

  The shape of the electrode body is determined according to the shape of the battery to be manufactured. For example, a disk-shaped or card-shaped positive electrode and negative electrode can be made to face each other to form a circular or card-type battery electrode body. Also, a plurality of card-shaped positive electrodes and negative electrodes are used, and the layers are alternately stacked. Also, the electrode body of a square battery can be formed by overlapping. Furthermore, the belt-like positive electrode and negative electrode can be wound to form an electrode body of a cylindrical battery. Also, the size of the electrode body is appropriately determined according to the application, but the present invention can also be applied to an electrode body or battery having a shape structure that could not be manufactured conventionally.

Examples of the present invention will be described below, but the present invention is not limited thereto.
As the polymer electrolyte, for example, dipentaerythritol polyacrylate polyundecylate, mixed monomer of polyethylene glycol diacrylate and ethylene oxide modified trimethylolpropane triacrylate, and dipentaerythritol hexaacrylate can be used. The lithium secondary battery of the present invention using dipentaerythritol hexaacrylate will be described.

<Adjustment of electrode slurry>
A positive slurry and a negative slurry were prepared by kneading and dispersing with a planetary mixer according to the composition shown below.

(Positive electrode slurry composition)
LiNi _0.82 Co _0.15 Al _0.03 O ₂ (active material): 44.0 parts LiCoO ₂ (Active material): 19.4 parts Acetylene black (Conductive material): 1.4 parts Polyvinylidene fluoride (Binder): 2.8 parts N-methylpyrrolidone (Solvent): 32.4 parts

(Negative electrode slurry composition)
Amorphous carbon surface-covered graphite (active material): 38.7 parts Mesocarbon microbeads (active material): 7.8 parts Styrene butadiene rubber (binder): 0.9 parts Carbomethoxycellulose: 0.4 parts Ion exchange Water: 52.2 parts

<Adjustment of electrolyte>
The raw materials used for the preparation of the electrolytic solution are as follows. And it melt | dissolved according to the composition shown below, and prepared the uniform electrolyte solution.

(Electrolytic solution composition)
Propylene carbonate: 35.4 parts Ethylene carbonate: 38.8 parts LiPF ₆ : 18.5 parts Dipentaerythritol hexaacrylate: 7.1 parts Cross-linking initiator (Trigonox 23C-70): 0.2 parts

<Manufacture of secondary batteries>
First, a coating for positive electrode is applied on one side of aluminum foil having a thickness of 15 μm by a doctor blade and dried to obtain a sheet on which a positive electrode active material layer having a basis weight of 9.20 mg / cm ² and having voids is formed. It was. Thereafter, calendering was performed to obtain a final layer thickness of about 48 μm.
In the same manner as described above, a negative electrode coating material was applied on one side onto a 10 μm thick copper foil and dried to obtain a sheet having a weight per unit area of 5.15 mg / cm ² and a negative electrode active material layer having voids formed thereon. . next,
Calendering was performed to obtain a final layer thickness of about 48 μm. Thereafter, the coating film was re-dried at 120 ° C. in a dry environment, and then punched into a predetermined shape.

  Next, a positive electrode sheet and a negative electrode sheet were laminated with a 12 μm-thick polyethylene microporous film in between, and a positive lead and a negative lead were attached to the tab portions of the positive electrode sheet and the negative electrode sheet, respectively, to obtain a battery element A. (See Figure 1)

  The battery element A was sandwiched between aluminum laminates, a polymer electrolyte solution was added, and the positive electrode sheet active material layer, the negative electrode sheet active material layer, and the separator were impregnated with the polymer electrolyte solution and vacuum-sealed to obtain a battery element B. (See Figure 2)

  A 30 mm square polyethylene microporous film impregnated with the electrolytic solution was sandwiched between polyethylene terephthalate sheets and vacuum-sealed with an aluminum laminate to obtain a microporous film evaluation sample A.

The battery element B was irradiated with an X-ray having an output of 60 kV and 66 mA for 60 seconds to obtain a lithium ion polymer secondary battery having a 0.2C capacity of 21.0 mAh.
During the X-ray irradiation, the battery element B did not generate heat.
The microporous film evaluation sample A was irradiated with an X-ray having an output of 60 kV and 66 mA for 60 seconds, and then the lengths of the microporous film in the MD direction and the TD direction were measured.
There was no shrinkage of the microporous film with a MD direction length of 30 mm and a TD direction length of 30 mm.

A lithium ion polymer secondary battery having a 0.2C capacity of 20.6 mAh was obtained in the same manner as in Example 1 except that the battery element B was irradiated with an X-ray having an output of 60 kV and 66 mA for 120 seconds.
During the X-ray irradiation, the battery element B did not generate heat.
The microporous film evaluation sample A was irradiated with an X-ray having an output of 60 kV and 66 mA for 120 seconds, and then the lengths of the microporous film in the MD direction and the TD direction were measured.
There was no shrinkage of the microporous film with a MD direction length of 30 mm and a TD direction length of 30 mm.

A lithium ion polymer secondary battery having a 0.2C capacity of 20.6 mAh was obtained in the same manner as in Example 1 except that the battery element B was irradiated with an X-ray having an output of 60 kV and 66 mA for 250 seconds.
During the X-ray irradiation, the battery element B did not generate heat.
The microporous film evaluation sample A was irradiated with X-rays having an output of 60 kV and 66 mA for 250 seconds, and then the lengths of the microporous film in the MD direction and the TD direction were measured.
There was no shrinkage of the microporous film with a MD direction length of 30 mm and a TD direction length of 30 mm.
[Comparative Example 1]

A battery element B was produced in the same manner as in Example 1 except that thermal polymerization was performed at 115 ° C. for 10 minutes to obtain a lithium ion polymer secondary battery having a 0.2C capacity of 21.6 mAh.
The microporous film evaluation sample A was heat-treated at 115 ° C. for 10 minutes, and then the lengths of the microporous film in the MD direction and the TD direction were measured.
The microporous film was shrunk with a MD direction length of 28.5 mm and a TD direction length of 29.5 mm.
[Comparative Example 2]

A battery element B was produced in the same manner as in Example 1 except that thermal polymerization was performed at 95 ° C. for 10 minutes to obtain a lithium ion polymer secondary battery having a 0.2C capacity of 20.5 mAh.
The microporous film evaluation sample A was heat-treated at 95 ° C. for 10 minutes, and then the length of the microporous film in the MD direction and the TD direction was measured.
The MD film had a length of 29.0 mm and a TD direction length of 29.5 mm, and the microporous film was shrunk.
[Comparative Example 3]

A battery element B was produced in the same manner as in Example 1 except that thermal polymerization was performed at 75 ° C. for 10 minutes to obtain a lithium ion polymer secondary battery having a 0.2C capacity of 20.0 mAh.
The microporous film evaluation sample A was heat-treated at 75 ° C. for 10 minutes, and then the lengths of the microporous film in the MD direction and the TD direction were measured.
There was no shrinkage of the microporous film with a MD direction length of 30 mm and a TD direction length of 30 mm.
[Comparative Example 4]

A battery element B was produced in the same manner as in Example 1 except that thermal polymerization was performed at 50 ° C. for 10 minutes to obtain a lithium ion polymer secondary battery having a 0.2C capacity of 20.1 mAh.
The microporous film evaluation sample A was heat-treated at 50 ° C. for 10 minutes, and then the length of the microporous film in the MD direction and the TD direction was measured.
There was no shrinkage of the microporous film with a MD direction length of 30 mm and a TD direction length of 30 mm.

<Capacity check>
In a 24 ° C environment, charge at a constant current and a constant voltage with a charge current of 0.5C and a charge voltage of 4.20V.
Charging was terminated when the current value C / 20 was reached. After the completion of charging, the discharge current was 0.2 C and the final voltage was 3.00 V. The discharge capacity was 0.2 C discharge capacity.

  The results of Examples 1 to 3 and Comparative Examples 1 to 4 are summarized as shown in Table 1.

As Table 1, what superposed | polymerized by the X-ray in Examples 1-3 has a high 0.2C capacity | capacitance, and there was no shrinkage | contraction of a microporous film.
In addition, as in Comparative Examples 1 and 2, thermal polymerization at 95 ° C. to 115 ° C. by the conventional method had a high 0.2C capacity, but the microporous film contracted. As in Comparative Examples 3 and 4, those thermally polymerized at 50 ° C. to 75 ° C. by the conventional method did not cause shrinkage of the microporous film, but there was a problem that the 0.2C capacity was lowered.
Shrinkage of the microporous film is not preferable because it causes an internal short circuit of the battery.
In addition, the completion of the polymerization at room temperature makes it possible to provide a range of battery designs from the viewpoint that a low boiling point solvent can be used.

  According to the present invention, it has been demonstrated that it is possible to provide a lithium ion polymer battery using an improved Liechs-ray polymerization monomer in a polymer electrolyte. The lithium ion polymer battery of the present invention improves productivity and increases the degree of freedom in the shape of the battery, so that it can be made into a complicated shape, such as a mobile phone, a game machine, a portable TV, a laptop computer, and a calculator. As a power source for small electronic devices such as HEVs (hybrid vehicles), EVs (electric vehicles), wireless cleaners, electric bicycles, electric scooters, etc. It can be effectively used as a high output energy source for driving the motor. In addition, it is expected to provide a product that has a high energy density and can fully utilize the characteristics of a lithium ion polymer battery with improved rate characteristics and charge / discharge cycle characteristics.

1: Positive lead 2: Positive electrode current collector 3: Positive electrode active material layer 4: Porous film 5: Negative lead 6: Negative electrode current collector 7: Negative electrode active material layer 8: Aluminum laminate

Claims (10)

  A lithium polymer secondary battery having a positive electrode, a negative electrode, and an ion conductive polymer electrolyte layer, wherein the ion conductive polymer electrolyte layer comprises an ion conductive polymer electrolyte composition cured by X-ray irradiation. battery.   An ion conductive polymer electrolyte composition is a monomer selected from an acrylic acid-based monomer having an unsaturated double bond obtained by esterifying a terminal hydroxyl group of an ester of acrylic acid with a polyhydric alcohol or a polyether polyol with acrylic acid. The lithium polymer secondary battery according to claim 1, which is contained.   3. The lithium according to claim 2, wherein the polyhydric alcohol or the polyether polyol is one or more selected from ethylene glycol, propylene glycol, butylene glycol, trimethylolpropane, pentaerythritol, and polyethers derived therefrom. Ion secondary battery.   The lithium polymer secondary battery according to any one of claims 1 to 3, wherein the ion conductive polymer electrolyte composition contains an additive having a boiling point of 130 ° C or lower.   The lithium polymer secondary battery according to any one of claims 1 to 4, wherein the X-ray irradiation is an irradiation time of 30 seconds to 5 minutes.   In a method for producing a lithium polymer secondary battery having a positive electrode, a negative electrode, and an ion conductive polymer electrolyte layer, the ion conductive polymer electrolyte layer is formed by irradiating and curing the ion conductive polymer electrolyte composition with X-rays A method for producing a lithium polymer secondary battery.   The ion conductive polymer electrolyte composition contains a monomer selected from an acrylic acid-based monomer having an unsaturated double bond obtained by esterifying a terminal hydroxyl group of acrylic acid polyhydric alcohol ester or polyether polyol with acrylic acid. The manufacturing method of the lithium polymer secondary battery of Claim 6.   The lithium according to claim 7, wherein the polyhydric alcohol or the polyether polyol is one or more selected from ethylene glycol, propylene glycol, butylene glycol, trimethylolpropane, pentaerythritol, and polyethers derived therefrom. A method for manufacturing an ion secondary battery.   The method for producing a lithium polymer secondary battery according to any one of claims 6 to 8, wherein the ion conductive polymer electrolyte composition contains an additive having a boiling point of 130 ° C or lower. The method for producing a lithium polymer secondary battery according to any one of claims 6 to 9, wherein the X-ray is irradiated for 30 seconds to 5 minutes.