JP2008146974A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery which is of a light weight and thin type as well as flexible and excellent in its reliability in a charge/discharge cycle property by using a resin molding such as resin film as a substrate. <P>SOLUTION: The secondary battery 1 is provided with a cell structure body with a positive electrode layer 35, a solid electrolyte layer 40 and a negative electrode layer 65 laminated in this order or in a reverse order on at least one surface side of the substrate 10. The substrate 10 is the resin molding obtained by photocuring a photocurable composite. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a secondary battery such as a lithium secondary battery. In particular, the present invention relates to an all-solid-state secondary battery that can be reduced in weight, thickness, and flexibility.

  Currently, secondary batteries such as lithium ion secondary batteries are widely used mainly in electronic devices such as portable devices. This is because a lithium ion secondary battery has a higher voltage, a larger charge / discharge capacity, and no adverse effects such as a memory effect, compared to a nickel cadmium battery or the like. Electronic devices and the like have been increasingly reduced in weight and thickness, and lithium ion secondary batteries are also required to be reduced in weight and thickness as batteries to be mounted on the electronic devices and the like. In recent years, a lightweight, thin, and flexible lithium ion secondary battery that can be mounted on an IC card, a flexible display, or the like is also required.

Conventional lithium ion secondary batteries are used by using metal pieces or metal foils for positive and negative electrodes, immersing them in an electrolytic solution, and covering them with a container. For this reason, there is a limit to reducing the weight and thickness. Recently, a thin-film solid secondary battery using a solid electrolyte (for example, see Patent Document 1) has been proposed. As described in Patent Document 1, a thin film solid secondary battery was formed by sequentially stacking a positive electrode current collector thin film, a positive electrode active material thin film, a solid electrolyte thin film, a negative electrode active material thin film, and a negative electrode current collector thin film on a substrate. A configuration or a configuration in which the above layers are stacked in reverse order on a substrate. With such a configuration, the thin-film solid secondary battery can be made as thin as 10 μm or less except for the substrate. Furthermore, by using a resin film as a substrate, it is possible to produce a lightweight, thin and flexible solid secondary battery.
JP 2005-251417 A

  As described above, a thin-film solid secondary battery using a resin film is expected to be lightweight and thin and flexible. However, it is not easy to actually manufacture a battery using a resin film as a substrate. There is a need for a resin film that can be easily formed into a thin film and that can ensure reliability as a battery. Specifically, it needs to have high surface smoothness, moderate bending elastic modulus, low water absorption, high heat resistance, low linear expansion coefficient, and the like. Among these, surface smoothness and bending elastic modulus are particularly important. If the surface is inferior in smoothness, the thin films that should not be in contact with each other may be in contact with each other. For example, when the negative electrode active material and the positive electrode active material are in contact with each other, a short circuit may occur inside the battery. Since a plurality of thin films are stacked on the substrate, the smoothness of the substrate greatly affects the yield of battery manufacturing. In addition, when the flexural modulus is low, warping and undulation are generated in the resin film in the thin film forming process, so that a flat battery cannot be formed, causing a short circuit.

  On the other hand, vanadium oxide and niobium oxide are generally used for the negative electrode active material thin film of the thin film solid secondary battery in order to improve battery performance. However, since these substances are vulnerable to moisture, moisture in the atmosphere may enter the negative electrode active material thin film through a resin film or the like, and may shorten the life of the negative electrode active material. Therefore, there also exists a subject that it is inferior to reliability, such as charging / discharging cycling characteristics.

  An object of the present invention is to provide a secondary battery that is lightweight, thin, flexible, and excellent in reliability such as charge / discharge cycle characteristics, using a resin molded body such as a resin film.

  In a secondary battery using a resin molded body as a substrate, the present inventors use a resin molded body obtained by photocuring a photocurable composition, thereby being lightweight, thin and excellent in flexibility, charging and discharging. It has been found that a secondary battery having excellent reliability such as cycle characteristics can be obtained.

  That is, the gist of the present invention is a secondary battery having a battery structure in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated in this order or in reverse order on at least one surface side of the substrate, It is a secondary battery characterized by being a resin molding obtained by photocuring a photocurable composition.

  The secondary battery of the present invention is lightweight, thin and flexible, and has excellent reliability such as charge / discharge cycle characteristics.

  Hereinafter, the present invention will be described in more detail. In the following, “(meth) acrylate” is a general term for acrylate and methacrylate.

  The secondary battery of the present invention includes a resin molded body as a substrate obtained by photocuring a photocurable composition, a positive electrode layer, a solid electrolyte layer, and a resin layer on one side or both sides of the resin molded body. The negative electrode layer has a battery structure laminated in this order or reverse order. Further, the secondary battery of the present invention may have a layer structure in which a pair of resin molded bodies sandwich a battery structure. Furthermore, you may have the layer structure by which the resin molding and the battery structure were laminated | stacked repeatedly. For example, a secondary battery having a configuration of substrate / positive electrode layer / solid electrolyte layer / negative electrode layer / substrate / positive electrode layer / solid electrolyte layer / negative electrode layer / substrate may be used.

(Photocurable composition)
Although a photocurable composition is not specifically limited, From the point of heat resistance or a low linear expansion coefficient, what contains a polyfunctional (meth) acrylate type compound and a photoinitiator is preferable.

Such polyfunctional (meth) acrylate compounds include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) ) Acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 2,2-bis [4- (Meth) acryloyloxyphenyl] propane, ethylene oxide modified bisphenol A type di (meth) acrylate, propylene oxide modified bisphenol A-type di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether Di (meth) acrylate, diglycidyl phthalate di (meth) acrylate, bis (hydroxy) tricyclo [5.2.1.0 ^2,6 ] decane = di (meth) acrylate, bis (hydroxymethyl) tricyclo [5 .2.1.0 ^2,6 ] decane = di (meth) acrylate, bis (hydroxy) pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13 ] pentadecane = di (meth) acrylate, bis (hydroxymethyl) pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13 ] pentadecane = di (meth) acrylate, 2,2-bis [4- (β- (meth) acryloyloxyethoxy) cyclohexyl] propane, 1,3-bis ((meth) acryloyloxymethyl) cyclohexane, 1,3-bis ((meth) acryloyloxyethyloxymethyl) cyclohexane, 1,4-bis ((meth) acryloyloxymethyl) cyclohexane, 1,4-bis ((meth) acryloyloxyethyloxymethyl) cyclohexane, hydroxy Bifunctional (meth) acrylate compounds such as pivalic acid-modified neopentyl glycol di (meth) acrylate, isocyanuric acid ethylene oxide-modified diacrylate, 2-acryloyloxyethyl acid phosphate diester; Acrylate), 1,3,5-tris ((meth) acryloyloxymethyl) cyclohexane, 1,3,5-tris ((meth) acryloyloxyethyloxymethyl) cyclohexane, pentaerythritol tri (meth) acrylate, pentaerythritol Tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly (meth) acrylate, isocyanuric acid ethylene oxide modified Triacrylate, ethylene oxide modified dipentaerythritol penta (meth) acrylate, ethylene oxide modified dipentaerythritol hexa (meth) Acrylate, ethylene oxide modified pentaerythritol tri (meth) acrylate, trifunctional or more (meth) acrylate compounds such as ethylene oxide modified pentaerythritol tetra (meth) acrylate. Furthermore, polyfunctional (meth) acrylate compounds such as epoxy (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, and polyether (meth) acrylate are exemplified.

Among these, from the viewpoint of heat resistance and toughness, bis (hydroxy) tricyclo [5.2.1.0 ^2,6 ] decane = di (meth) acrylate, bis (hydroxymethyl) tricyclo [5.2.1]. 0.0 ^2,6 ] decane = di (meth) acrylate and urethane (meth) acrylate are particularly preferred. Moreover, the said polyfunctional (meth) acrylate type compound can also use 1 type (s) or 2 or more types. Furthermore, you may use together the said polyfunctional (meth) acrylate type compound and a monofunctional (meth) acrylate type compound.

  The photopolymerization initiator used in the present invention is not particularly limited, and specifically includes 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 4-diphenoxy. Examples include acetophenone-based initiators such as dichloroacetophenone, benzophenone-based initiators such as benzophenone, methyl benzoylbenzoate, 4-phenylbenzophenone, and hydroxybenzophenone, and these can also be used in combination. These photopolymerization initiators are 100 parts by mass of a polyfunctional (meth) acrylate compound (when a monofunctional (meth) acrylate compound is used in combination, a polyfunctional (meth) acrylate compound and a monofunctional (meth) acrylate compound) It is preferable to use normally in the ratio of 0.1-10 mass parts with respect to a total of 100 mass parts), Especially preferably, it is 1-5 mass parts. If the amount of the photopolymerization initiator is too small, curing tends to not proceed sufficiently, and if it is too large, the mechanical strength of the resulting resin sheet tends to decrease.

  The photocurable composition used in the present invention preferably further contains a tetrafunctional mercaptan compound represented by the following general formula (1) from the viewpoint of flexural modulus and low water absorption.

(In the formula, R ³ is an alkylene group having 1 to 5 carbon atoms.)

  Specific examples of the tetrafunctional mercaptan-based compound represented by the general formula (1) include pentaerythritol tetrakisthioglycolate, pentaerythritol tetrakisthiopropionate, and the like. The content of the tetrafunctional mercaptan compound is based on the total of the polyfunctional (meth) acrylate compound (when the monofunctional (meth) acrylate compound is used in combination, the polyfunctional (meth) acrylate compound and the monofunctional ( It is preferable that it is 1-30 mass% with respect to the sum total with a (meth) acrylate type compound. More preferably, it is 5-20 mass%, More preferably, it is 10-15 mass%. If the content of the tetrafunctional mercaptan-based compound is too large, the flexural modulus of the resulting resin molded product tends to decrease. Conversely, if the content is too small, the flexural modulus of the resin molded product is too high. Tend to decrease.

The photocurable composition suitable for the present invention is bis (hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] decane = di (meth) acrylate and a tetrafunctional compound represented by the above general formula (1). It is a composition obtained by containing a mercaptan compound and a photopolymerization initiator. In this composition, as the photopolymerization initiator, those exemplified above can be used, and the content thereof is bis (hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] decane = di (meth) acrylate. It is preferable to use normally in the ratio of 0.1-10 mass parts with respect to 100 mass parts, Especially preferably, it is 1-5 mass parts.

  In addition to the above, auxiliary ingredients such as antioxidants, ultraviolet absorbers, mold release agents, antistatic agents, flame retardants, antifoaming agents, colorants, and various fillers are added to the photocurable composition. Also good.

(Light curing)
The method for photocuring the above-mentioned photocurable composition is not particularly limited as long as it is a photomolding method using a translucent member having a smooth inner surface as a mold. The surface roughness (Ra) in JIS B 0601: 2001 of the translucent member is preferably 15 nm or less, more preferably 12 nm or less, still more preferably 10 nm or less, and particularly preferably 9 nm or less. “Translucent” means that the following active energy rays can be transmitted.

  A specific example of the translucent member is an optically polished glass plate from which minute irregularities on the surface are removed by abrasive grains or the like. An optical molding method using an optically polished glass plate is, for example, as follows. A molding die in which two optical polishing glass plates are opposed to each other through a spacer for controlling the thickness is produced. A photocurable composition is injected into the cavity, cured by irradiation with active energy rays, and demolded.

As the active energy rays, rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, electromagnetic waves such as X rays and γ rays, electron beams, proton rays, neutron rays, etc. can be used. Ultraviolet irradiation is advantageous from the viewpoint of availability and price. As a light source for ultraviolet irradiation, a chemical lamp, a xenon lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, or the like is used. In the case of performing ultraviolet irradiation, it is preferable to use 200 to 400 nm ultraviolet light and to photocure at an irradiation light amount of 20 J / cm ² or less. If the irradiation light quantity is too large, the productivity tends to be inferior. The illuminance of ultraviolet rays is preferably 10 to 5000 mW / cm ² , more preferably 100 to 1000 mW / cm ² . When the illuminance is too small, there is a tendency that the resin molded body is not sufficiently cured. On the other hand, if the illuminance is too high, polymerization tends to run away and cracks tend to occur. In addition, light irradiation may be performed in several steps for relaxation of curing shrinkage, or may be performed while heating for improving the curing rate. In addition, the resin molded body obtained by photocuring may be heat-treated for improving the degree of polymerization or releasing stress strain.

[Resin molding]
The resin molding obtained by the above-mentioned photocuring has a highly crosslinked structure, and is a substrate having high heat resistance, a low linear expansion coefficient, and an appropriate bending elastic modulus. The thickness of the resin molded body is preferably 0.1 to 0.5 mm, more preferably 0.2 to 0.4 mm, and still more preferably 0.2 to 0.3 mm. If the thickness is too thin, the rigidity as a battery support tends to be insufficient, and if it is too thick, it tends to be difficult to make the battery thinner and lighter and flexible.

  The resin molded body used in the present invention preferably has a surface roughness (Ra) according to JIS B 0601: 2001 of the surface on the battery structure side of preferably 20 nm or less, more preferably 15 nm or less, still more preferably 12 nm or less, particularly preferably. 10 nm or less. If the surface roughness (Ra) is too large, the production yield of the battery tends to decrease due to insufficient surface smoothness. In general, the lower limit of the surface roughness (Ra) is 1 nm. Further, when the battery structure is provided on both surfaces of the resin molded body, the surface roughness (Ra) of both surfaces of the resin molded body is preferably within the above range, and the battery is formed on one surface of the resin molded body. When a structure is provided, the surface roughness (Ra) of the surface opposite to the battery structure is not particularly limited, but is preferably within the above range.

  The surface smoothness described above is difficult to achieve with a resin molding method using a mold. Although a method of polishing the surface of the resin molded body and a method of coating the surface are possible, it is difficult not only to increase the cost but also to avoid the foreign matter problem even if the cleanness of the process atmosphere is increased.

  As a result of intensive studies, the present inventors have obtained a resin molded body obtained by photocuring a photocurable composition using a translucent member having a surface roughness equivalent to the surface smoothness described above as a mold. It was found that the surface smoothness described above was satisfied. That is, it has been found that surface smoothness capable of forming a thin film and ensuring the reliability of the battery can be obtained by transferring the surface of the translucent member to the resin surface.

  The resin molded body used in the present invention preferably has a flexural modulus of 3 to 4 GPa. Since the crosslinkable resin has a three-dimensional network structure, it is difficult to be deformed even in the battery manufacturing process, and an appropriate bending elastic modulus can be set depending on the resin composition. A preferable range of the flexural modulus is 3.3 to 3.9 GPa, more preferably 3.5 to 3.8 GPa. If the flexural modulus is too high, the flexibility of the battery tends to be reduced. Conversely, if the flexural modulus is too low, the substrate tends to swell and warp when forming a thin film, and the function as a support tends to be inferior. is there. In addition, the measuring method of a bending elastic modulus is mentioned later in a following example.

  Furthermore, the resin molding used in the present invention preferably has a water absorption of 1% or less. More preferably, it is 0.8% or less, More preferably, it is 0.7% or less. Since the positive electrode layer, the solid electrolyte layer, and the negative electrode layer constituting the battery structure are easily deteriorated by moisture, if the water absorption rate of the resin molded body is too high, the durability of the battery tends to decrease. Usually, the lower limit of water absorption is 0.01%. In addition, the measuring method of a water absorption rate is later mentioned in the following Example.

  Moreover, the resin molding used by this invention is excellent in heat resistance, and has a glass transition temperature of 100 degreeC or more.

[Battery structure]
A battery structure provided on one side or both sides of a resin molded body (substrate) has a layer structure in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated in this order or in reverse order.

  In general, the positive electrode layer is preferably formed of a positive electrode current collector layer and a positive electrode active material layer. The positive electrode current collector layer and the positive electrode active material layer are not limited to those that can be distinguished as different layers, and may be recognized as the same layer that performs each function.

  As the positive electrode current collector layer, a metal thin film having good adhesion between the substrate and the positive electrode active material layer and having low electric resistance is preferably used. For example, vanadium, aluminum, copper, nickel, gold or the like can be used. Among these, vanadium is particularly preferable from the viewpoint of a low resistance value. The film thickness of the positive electrode current collector layer is preferably 100 to 1000 nm, particularly preferably 200 to 500 nm, in terms of low resistance. In addition, the sheet resistance value of the positive electrode current collector layer is desirably 1 kΩ / □ or less in order to function well as an extraction electrode.

The positive electrode active material layer is not particularly limited, but an active material layer containing a metal oxide containing lithium as a constituent element is preferable. For example, lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), or the like can be used. The thickness of the positive electrode active material layer is desirably as thin as possible, but is preferably about 1000 nm in order to ensure charge / discharge capacity.

The solid electrolyte layer is not particularly limited, and lithium phosphate (Li ₃ PO ₄ ) having a good lithium ion conductivity, a substance obtained by adding nitrogen to this (LiPON), a gel electrolyte, a polymer electrolyte, or the like can be used. . Among these, lithium phosphate _(Li 3 PO ₄₎ and this was added nitrogen material (LiPON) is preferred. The film thickness of the solid electrolyte layer is preferably as thin as 500 to 30000 nm as much as possible to reduce the occurrence of pinholes. More preferably, it is about 1000 nm.

  In general, the negative electrode layer is preferably formed of a negative electrode current collector layer and a negative electrode active material layer. The negative electrode current collector layer and the negative electrode active material layer are not limited to those that can be distinguished as different layers, and may be recognized as the same layer that performs each function.

The negative electrode active material layer is not particularly limited, and can be formed using vanadium pentoxide, niobium pentoxide, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), or zinc oxide (ZnO). The film thickness of the negative electrode active material layer is desirably 100 nm or more in order to ensure charge / discharge capacity. More preferably, it is 100 to 10,000 nm for shortening the film formation time. More preferably, the thickness is 300 to 1000 nm in order to avoid inconvenience of peeling after film formation and to ensure good adhesion.

  As the negative electrode current collector layer, a metal thin film having good adhesion between the substrate and the negative electrode active material layer and having low electric resistance can be used as in the positive electrode current collector layer. For example, vanadium, aluminum, copper, nickel, gold or the like can be used. Among these, vanadium is particularly preferable from the viewpoint of a low resistance value. The film thickness of the negative electrode current collector layer is preferably from 100 to 1000 nm, particularly preferably from 200 to 500 nm, in terms of low resistance. In addition, the sheet resistance value of the negative electrode current collector layer is desirably 1 kΩ / □ or less in order to function well as the extraction electrode.

  In the present invention, the positive electrode layer / solid electrolyte / negative electrode layer preferably has a positive electrode current collector layer / positive electrode active material layer / solid electrolyte layer / negative electrode active material layer / negative electrode current collector layer. As a film formation method for each of the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector layer, a dry process such as a sputtering method, an electron beam evaporation method, a heating evaporation method, Known methods such as a wet process such as spin coating, die coating, and screen printing can be used. It is preferable to use a dry process that can form a thin and uniform thin film. More preferably, it is preferable to use a sputtering method in which there is little deviation in the atomic composition from the vapor deposition material and uniform film formation is possible.

[Water vapor barrier film]
In the present invention, it is preferable that a water vapor barrier film is laminated on at least one of the both surfaces of the substrate and the outer surface of the battery structure. When the water vapor barrier film is formed on the substrate, it may be an outer surface in contact with the air or an inner surface in contact with the inner layer (positive electrode current collector layer or negative electrode current collector layer) of the battery structure. In addition, a water vapor barrier film may be formed on the outer surface of the outer layer (negative electrode current collector layer or positive electrode current collector layer) of the battery structure. By forming the water vapor barrier film in this way, it is possible to prevent moisture in the atmosphere from entering the negative electrode active material thin film, and thus the battery performance can be kept longer. As the water vapor barrier film, silicon oxide, silicon nitride, a mixture thereof, or the like can be used. The film thickness of the water vapor barrier film is preferably about 10 to 500 nm, which is as thin as possible and has a high moisture prevention effect.

  As a method for forming the water vapor barrier film, a known method such as a dry process such as a sputtering method, an electron beam vapor deposition method, or a heat vapor deposition method, or a wet process such as spin coating, die coating, or screen printing can be used. It is preferable to use a dry process that can form a thin and uniform thin film. More preferably, a sputtering method capable of uniformly forming a film is used.

  When the all-solid-state lithium secondary battery is charged, lithium is separated from the positive electrode active material layer as ions and inserted into the negative electrode active material layer through the solid electrolyte layer. At this time, electrons are emitted from the positive electrode active material layer to the outside. Further, at the time of discharge, lithium is separated from the negative electrode active material layer as ions, and is occluded in the positive electrode active material layer through the solid electrolyte layer. At this time, electrons are emitted from the negative electrode active material layer to the outside.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded. In the examples, “parts” and “%” mean mass basis unless otherwise specified. The measuring method of each physical property is as follows. The results are summarized in Table 1.

(1) Surface smoothness
According to JIS B 0601: 2001, the surface roughness Ra (nm) of the resin sheet was measured using “Surfcom 570A” manufactured by Tokyo Seimitsu Co., Ltd. (cutoff: 100 μm, measurement length: 14 mm).
(2) Flexural modulus Using “Autograph AG-5kNE” (20 mm distance between fulcrums, 0.5 mm / min) manufactured by Shimadzu Corporation using a test piece of length 25 (mm) × width 10 (mm) Measured at 25 ° C.

(3) Water absorption rate According to JIS K7209, 100% (mm) x 100 (mm) size test pieces were dried at 50 ° C for 24 hours and then immersed in water at 23 ° C for 24 hours (% ) Was measured.
(4) Charging / discharging characteristic It measured using the charging / discharging measuring device. The measurement conditions are that the current during charging and discharging is 400 μA, and the voltage at the end of charging and discharging is 3.5 V and 0.3 V, respectively.

(Example 1)
[Manufacture of resin substrates]
Bis (hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] decane dimethacrylate (“DCP” manufactured by Shin-Nakamura Chemical Co., Ltd.) 85 parts, pentaerythritol tetrakisthiopropionate (manufactured by Sakai Chemical Co., Ltd. 15 parts of PETP ”) and 1 part of 1-hydroxycyclohexyl phenyl ketone (“ Irgacure 184 ”manufactured by Ciba Geigy Co., Ltd.) as a photopolymerization initiator were stirred at 60 ° C. until uniform, to obtain a photocurable composition. This composition was poured into a mold composed of two optical polishing glass plates facing each other with a silicon plate having a thickness of 1.0 mm as a spacer (23 ° C.), and an illuminance of 100 mW / cm ² using a metal halide lamp. UV light was irradiated at a light amount of 10 J / cm ² . The cured product obtained by demolding was heated in a vacuum oven at 150 ° C. for 2 hours to obtain a resin molded body (hereinafter referred to as a resin substrate) having a width of 10 cm × length of 10 cm × thickness of 0.2 mm. . In addition, the surface roughness (Ra) of the used optical polishing glass is 4 nm.

  As shown in Table 1, the obtained resin substrate has a flexural modulus of 3.8 GPa, a water absorption of 0.5%, a surface roughness (Ra) of 5 nm, and has good performance as a resin substrate. It was.

[Production of battery]
Using the obtained resin substrate, an all solid lithium secondary battery 1 shown in FIG. 1 was produced. A lithium secondary battery 1 shown in FIG. 1 has a battery structure 2 on a resin substrate 10. The battery structure 2 was produced by forming the positive electrode current collector layer 20, the positive electrode active material layer 30, the solid electrolyte layer 40, the negative electrode active material layer 50, and the negative electrode current collector layer 60 in this order by a sputtering method. The positive electrode current collector layer 20 and the positive electrode active material layer 30 constitute a positive electrode layer 35, and the negative electrode active material layer 50 and the negative electrode current collector layer 60 constitute a negative electrode layer 65.

  The positive electrode current collector layer 20 was formed by a DC magnetron sputtering method using a vanadium metal target. The film was formed with a DC power of 1 KW and no heating. As a result, a 300 nm vanadium thin film was formed as the current collector layer 20.

The positive electrode active material layer 30 was formed by RF magnetron sputtering using a sintered manganate (LiMn ₂ O ₄ ) sintered target and introducing oxygen. The film was formed with an RF power of 1 KW and no heating. As a result, a 1000 nm lithium manganate thin film was formed.

The solid electrolyte layer 40 was formed by RF magnetron sputtering using a sintered phosphor target of lithium phosphate (Li ₃ PO ₄ ) and introducing nitrogen gas. The film was formed with an RF power of 1 KW and no heating. Thereby, a lithium phosphate thin film of 1000 nm was formed.

  The negative electrode active material layer 50 was formed by a DC magnetron sputtering method using a vanadium pentoxide sintered compact target and introducing oxygen. The film was formed with a DC power of 1 KW and no heating. Thereby, a 500 nm vanadium pentoxide thin film was formed.

  The negative electrode current collector layer 60 was formed by a DC magnetron sputtering method using a vanadium metal target. The film was formed with a DC power of 1 KW and no heating. Thus, a 300 nm vanadium thin film was formed as the current collector layer 60.

[Battery evaluation]
The charge / discharge characteristics of the all-solid-type lithium secondary battery 1 obtained as described above were measured. As a result, it was confirmed that repeated charge / discharge operations were exhibited. As shown in Table 1, the discharge start voltage at the 10th cycle when the charge / discharge operation was stabilized was 3.1 V, and the charge capacity and discharge capacity were 940 μAh and 910 μAh, respectively. In this example, charge / discharge measurement was performed up to 100 cycles, but it was confirmed that a stable and substantially constant charge / discharge curve was exhibited. Furthermore, the charge / discharge characteristics of the all-solid-state lithium secondary battery 1 were measured again after about one month. As a result, as shown in Table 1, the discharge capacity was only reduced by 20%.

(Example 2)
[Manufacture of resin substrates]
80 parts of bis (hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] decane diacrylate (“A-DCP” manufactured by Shin-Nakamura Chemical Co., Ltd.), pentaerythritol tetrakisthiopropionate (Sakai Chemical Co., Ltd.) A resin substrate was obtained in the same manner as in Example 1, except that 20 parts of “PET” manufactured by the company and 1 part of 1-hydroxycyclohexyl phenyl ketone (“Irgacure 184” manufactured by Ciba Geigy Co., Ltd.) were used as the photopolymerization initiator. As shown in Table 1, the obtained resin substrate has a flexural modulus of 3.5 GPa, a water absorption of 0.7%, a surface roughness (Ra) of 5 nm, and has good performance as a resin substrate. It was.

[Production and evaluation of batteries]
In the same manner as in Example 1, an all-solid-type lithium secondary battery was produced, and its charge / discharge characteristics were measured. As a result, it was confirmed that repeated charge / discharge operations were exhibited. As shown in Table 1, the discharge start voltage at the 10th cycle when the charge / discharge operation was stable was 3.0 V, and the charge capacity and the discharge capacity were 931 μAh and 906 μAh, respectively. In this example, charge / discharge measurement was performed up to 100 cycles, but it was confirmed that a stable and substantially constant charge / discharge curve was exhibited. Furthermore, the charge / discharge characteristics of the all-solid-state lithium secondary battery were measured again after about one month. As a result, as shown in Table 1, the discharge capacity was only reduced by 25%.

(Example 3)
[Production of battery]
Using the resin substrate of Example 1, an all solid-state lithium secondary battery 2 shown in FIG. 2 was produced. A lithium secondary battery 2 shown in FIG. 2 has a battery structure 2 on one surface side of a resin substrate 10, similarly to the lithium secondary battery 1 of Example 1. However, a silicon nitride thin film as the water vapor barrier film 70 is formed on both surfaces of the resin substrate 10 and the outer surface of the negative electrode current collector layer 60 by a sputtering method. That is, the lithium secondary battery 2 of FIG. 2 has a structure in which the resin substrate 10 and the battery structure 2 are sandwiched between the water vapor barrier films 70. The water vapor barrier film 70 was formed using a Si semiconductor target and introducing nitrogen gas by RF magnetron sputtering. The film was formed with an RF power of 1 KW and no heating. As a result, a 100 nm silicon nitride thin film was formed.

[Battery evaluation]
In the same manner as in Example 1, the charge / discharge characteristics of the all solid-state lithium secondary battery 2 were measured. As a result, it was confirmed that repeated charge / discharge operations were exhibited. As shown in Table 1, the discharge start voltage at the 10th cycle when the charge / discharge operation was stabilized was 3.1 V, and the charge capacity and discharge capacity were 940 μAh and 910 μAh, respectively. In this example, charge / discharge measurement was performed up to 100 cycles, but it was confirmed that a stable and substantially constant charge / discharge curve was exhibited. Furthermore, the charge / discharge characteristics of the all-solid-state lithium secondary battery 2 were measured again after about one month. As a result, as shown in Table 1, the discharge capacity was only reduced by 5%.

(Comparative Example 1)
[Production of battery]
An all solid-state lithium secondary battery was produced in the same manner as in Example 1 except that an optically polished glass plate having a length of 100 mm, a width of 100 mm, and a thickness of 0.5 mm was used as the substrate. The surface roughness (Ra) of this optically polished glass plate is 4 nm.

[Battery evaluation]
In the same manner as in Example 1, the charge / discharge characteristics of the all-solid-state lithium secondary battery were measured. As a result, it was confirmed that repeated charge / discharge operations were exhibited. As shown in Table 1, the discharge start voltage at the 10th cycle in which the charge / discharge operation was stable was 3.1 V, and the charge capacity and discharge capacity were 948 μAh and 917 μAh, respectively. In this example, charge / discharge measurement was performed up to 100 cycles, but it was confirmed that a stable and substantially constant charge / discharge curve was exhibited. Furthermore, the charge / discharge characteristics of the all-solid-state lithium secondary battery were measured again after about one month. As a result, as shown in Table 1, the discharge capacity was only reduced by 20%. However, in this comparative example, since the bending elastic modulus of the glass plate exceeded 100 GPa, the flexibility was inferior.

(Comparative Example 2)
[Production of battery]
An all solid lithium secondary battery was produced in the same manner as in Example 1 except that a PET film was used as the substrate. The surface roughness (Ra) of this PET film is 50 nm.

[Battery evaluation]
In the same manner as in Example 1, the charge / discharge characteristics of the all-solid-state lithium secondary battery were measured. As a result, in the repeated charge / discharge operation, both the charge / discharge capacities decreased and the battery did not operate at the 10th cycle.

  The use of the secondary battery of the present invention is not particularly limited, and examples thereof include electronic devices such as portable terminals, cell motors such as automobiles and electric vehicles, and medical devices such as pacemakers.

1 is a cross-sectional view schematically showing an all solid state lithium secondary battery 1 of Example 1. FIG. 4 is a cross-sectional view schematically showing an all solid state lithium secondary battery 2 of Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,3 Secondary battery 2 Battery structure 10 Resin substrate 20 Positive electrode collector layer 30 Positive electrode active material layer 35 Positive electrode layer 40 Solid electrolyte layer 50 Negative electrode active material layer 60 Negative electrode current collector layer 65 Negative electrode layer 70 Water vapor barrier film

Claims (9)

A secondary battery having a battery structure in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated in this order or reverse order on at least one surface side of a substrate,
A secondary battery, wherein the substrate is a resin molded body obtained by photocuring a photocurable composition.   The secondary battery according to claim 1, wherein the substrate has a thickness of 0.1 to 0.5 mm, and a surface roughness (Ra) of the surface on the battery structure side is 20 nm or less.   The secondary battery according to claim 1 or 2, wherein the substrate has a flexural modulus of 3 to 4 GPa.   The secondary battery according to claim 1, wherein the substrate has a water absorption of 1% or less.   The secondary battery according to claim 1, wherein the photocurable composition contains a polyfunctional (meth) acrylate compound and a photopolymerization initiator. The secondary battery according to claim 5, wherein the photocurable composition further contains a tetrafunctional mercaptan-based compound represented by the following general formula (1).

(In the formula, R ³ is an alkylene group having 1 to 5 carbon atoms.)   The secondary battery according to any one of claims 1 to 6, wherein a water vapor barrier film is laminated on at least one surface of both surfaces of the substrate and the outer surface of the battery structure.   The secondary battery according to claim 1, wherein the positive electrode layer contains a metal oxide containing lithium.   The secondary battery according to claim 1, wherein the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are formed by a dry process.

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