JP2010135226A - Polymer electrolyte laminated lithium secondary cell with improved output performance, and method for improving output performance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte lithium secondary cell with improved output performance. <P>SOLUTION: The polymer electrolyte laminate lithium secondary cell has each layer (a cathode, cathode active material layer, separator, anode active material layer and anode) constituting a unit cell, laminated in turn, that makes up the thickness of the basic cell of ä((lamination number)-(natural number n))/(lamination number)} times a general cell used for a camera-integrated VTR, a cellphone, or a portable computer with output performance improved. The number of lamination is a multiple of 7; and the thickness of the basic cell of ä((lamination number)-(lamination number)/7)/(lamination number)} times is 268 μm, or the number of lamination is a multiple of 8; and a thickness of the basic cell of ä((lamination number)-(lamination number)×2/8)/(lamination number)} times is 234 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte laminated lithium secondary battery having improved output performance and a method for improving output performance, and more specifically, a general battery used in a camera-integrated VTR, a mobile phone, or a portable computer. [(Number of stacked layers−natural number n) / number of stacked layers] times the basic cell thickness of the polymer electrolyte stacked lithium secondary battery.

In recent years, air pollution caused by exhaust gas from automobiles has become a global problem, and electric cars powered by electricity and hybrid cars that run in combination with an engine and a motor are attracting attention and will be installed in these. The development of batteries with high energy density and high output density occupies an important industrial position. The battery configuration for such a use includes a positive and negative electrode, an active material that reversibly electrochemically reacts with lithium ions, and a non-aqueous electrolyte that is responsible for the movement of lithium ions, and can be charged and discharged. Lithium ion secondary batteries are known. There is also known a hybrid vehicle that includes an engine and a motor as a travel drive source and travels with both or any one of the drive forces. Some hybrid vehicles have been announced to be equipped with the lithium ion secondary battery described above.
By the way, the hybrid vehicle basically travels with a motor having higher driving efficiency than the engine in a low speed and light load region, and travels with an engine having higher driving efficiency than the motor in a high speed and high load region. Therefore, the motor is mainly used when starting, accelerating, or decelerating the vehicle, and the battery that supplies power to the motor is supplied with a large amount of power in a short time rather than a high energy density that supplies a small amount of power over a long period of time. A high power density is required.

However, research and development of conventional lithium-ion batteries has been promoted mainly for the purpose of improving energy density, and the energy density per volume and weight has reached a high level, but the output density is the requirement of the hybrid vehicle described above. It does not satisfy.
Lithium-ion secondary battery, the positive electrode active material layer made of an active material such as lithium cobalt oxide (LiCoO ₂₎ is formed on the positive electrode current collector, the negative electrode active material layer such as graphite is formed on an anode current collector These positive and negative active materials are arranged to face each other with a separator interposed therebetween. However, since resistance exists in the thickness direction of the active material layers of the positive electrode and the negative electrode, there has been a certain limit to increase the output. Therefore, it is possible to increase the capacity by using a composite oxide of lithium and copper that reversibly progresses by mixing copper oxide with graphite, which is the negative electrode active material, and electrochemically reducing this copper oxide. A technique for achieving this is disclosed (Patent Document 1). In this case, the weight of the electrode is increased, which is disadvantageous for increasing the output density.

Since the polymer electrolyte battery can be formed into a sheet shape of the electrode and the electrolyte, a thin battery can be manufactured. Batteries using polymer electrolytes have characteristics not found in conventional batteries in that they are particularly excellent in safety and storage properties including leakage resistance. However, in the manufacturing method using the winding type, the former has a thick end, and the electrolyte cannot penetrate into the inside, so that a thin battery cannot be manufactured. Therefore, a method of manufacturing a flat thin battery by laminating a plurality of electrodes has been proposed (for example, Patent Document 2 and Patent Document 4). However, in this multilayer battery, when the number of stacked electrodes is increased and the electric capacity and electric capacity density are increased, heat is generated, which may lead to accidents such as smoke, fire, and explosion.
Therefore, there is a laminated battery provided with a short circuit forming and heat dissipation promoting member (Patent Document 3), a battery having a laminated structure portion of an electrically conductive flat plate member / an electronic insulating flat plate member / an electrically conductive flat plate member (Patent Document 4). It has been recommended.
In addition, conventional lithium ion batteries have been researched and developed mainly for the purpose of improving energy density, and the energy density per unit volume and weight has reached a high level, but the output density is the requirement of the hybrid vehicle described above. In order to provide a high-power-density lithium ion secondary battery, positive and negative electrodes composed of an active material and a current collector that perform an electrochemical reaction with lithium ions, and lithium ions In a lithium ion secondary battery having an electrolyte for moving the lithium ion secondary battery, the active material has a coating thickness of 5 to 80 μm, more preferably 8 to 60 μm. (Patent Document 5). However, a film-like positive electrode material, a separator, and a negative electrode material are wound in a cylindrical shape, and the electrolytic solution is liquid.

JP-A-6-325753 JP 2000-30747 A JP 2001-68157 A Japanese Patent Application Laid-Open No. 2001-299795 JP 11-329409 A

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a polymer electrolyte lithium secondary battery with improved output performance. It seeks to provide a high power battery despite the same volume with little manufacturing or material changes.

  The present invention achieves the above object by reducing the thickness of the bicell to an acceptable range (to the extent that the function of the battery is not impaired) and increasing the number of stacked bicells instead. More specifically, for example, instead of the conventional 314 μm bicell × 6 pairs stacked, 268 μm × 7 pairs stacked, or 234 μm bicells × 8 pairs stacked, It is said that an unexpected output was obtained.

That is, the gist of the present invention is a polymer electrolyte laminated lithium secondary battery with improved output performances (1) to (6) below.
(1) In a polymer electrolyte laminated lithium secondary battery, each layer (positive electrode / positive electrode active material layer / separator (polymer electrolyte layer) / negative electrode active material layer / negative electrode) constituting a unit battery is sequentially laminated to form a camera-integrated VTR. Polymer electrolyte laminate with improved output performance characterized by having a basic cell thickness [(number of layers-natural number n) / number of layers] times that of a general battery used in mobile phones or portable computers Lithium secondary battery.
(2) One set of double-sided negative electrodes in which a negative electrode active material slurry is directly applied to both sides of a negative electrode current collector, each of which is preliminarily impregnated with an electrolyte containing a monomer, and a separator that is impregnated with the electrolyte Furthermore, a positive electrode in which an anode active material slurry is directly applied to one side of an anode current collector, and a bicell structure in which two sets each impregnated with the electrolyte are sequentially laminated and then heat-polymerized and integrated. The polymer electrolyte laminated lithium secondary battery according to (1), which is a unit battery.
(3) A positive electrode is a positive electrode in which a positive electrode active material containing LiCoO ₂ , LiNiO _2, or LiMn ₂ O ₄ is applied to one side of an aluminum foil, and a negative electrode active material containing graphite on both sides of a negative electrode of a copper foil The polymer electrolyte laminated lithium secondary battery according to (1) or (2), wherein the negative electrode is coated with a negative electrode.
(4) The polymer electrolyte laminated lithium secondary battery according to any one of (1) to (3), wherein (the number of stacked layers−natural number n) is a multiple of 6.
(5) The number of stacked layers is a multiple of 7, and the thickness of the basic cell [(number of stacked layers−number of stacked layers / 7) / number of stacked layers] times 268 μm is any one of (1) to (3) The polymer electrolyte laminated lithium secondary battery described.
(6) Any one of (1) to (3), wherein the number of stacked layers is a multiple of 8 and the thickness of the basic cell is [(number of stacked layers−number of stacked layers × 2/8) / number of stacked layers] times 234 μm. The polymer electrolyte laminated lithium secondary battery according to claim 1.

In addition, the gist of the present invention is a method for improving the output performance of the polymer electrolyte laminated lithium secondary battery of the following (7) to (12).
(7) In the polymer electrolyte laminated lithium secondary battery, each layer constituting the unit battery (positive electrode / positive electrode active material layer / separator / negative electrode active material layer / negative electrode) is sequentially laminated to form a camera-integrated VTR, a mobile phone, or Improve the output performance of a polymer electrolyte laminated lithium secondary battery characterized in that the thickness of the basic cell is [(number of layers-natural number n) / number of layers] times that of a general battery used in a portable computer. Method.
(8) One set of double-sided negative electrodes in which a negative electrode active material slurry is directly applied to both sides of a negative electrode current collector, each of which is preliminarily impregnated with an electrolyte containing a monomer, and a separator that is impregnated with the electrolyte And a positive electrode in which an anode active material slurry is directly applied to one side of an anode current collector, in which two sets each impregnated with the electrolytic solution are sequentially laminated, and then thermally polymerized to be integrated into a bicell structure (7) The method of improving the output performance of the polymer electrolyte laminated lithium secondary battery as described in (7).
(9) The positive electrode is a positive electrode in which a positive electrode active material containing LiCoO ₂ , LiNiO _2, or LiMn ₂ O ₄ is applied to one side of an aluminum foil, one set of negative electrodes includes an electrolyte solution, and graphite is formed on both sides of the negative electrode of the copper foil. A method for improving the output performance of the polymer electrolyte laminated lithium secondary battery according to (7) or (8), wherein the negative electrode active material is coated with a negative electrode active material.
(10) The method for improving the output performance of the polymer electrolyte laminated lithium secondary battery according to any one of (7) to (9), wherein (the number of stacked layers−natural number n) is a multiple of 6.
(11) The number of stacked layers is a multiple of 7, and the thickness of a basic cell [(number of stacked layers−natural number n) / number of stacked layers] times is 268 μm, according to any one of (7) to (9) A method for improving the output performance of a polymer electrolyte laminated lithium secondary battery.
(12) The number of stacked layers is a multiple of 8, and the thickness of a basic cell [(number of stacked layers−natural number n) / number of stacked layers] times is 234 μm, according to any one of (7) to (9) A method for improving the output performance of a polymer electrolyte laminated lithium secondary battery.

According to the present invention, a polymer electrolyte lithium secondary battery having improved output performance can be provided. Despite the same volume with almost no manufacturing changes or material changes, a high output battery can be provided.
That is, according to the present invention, by changing the thickness of each layer of the positive electrode / positive electrode active material layer / separator / negative electrode / negative electrode active material layer / negative electrode, the thickness of the bicell can be reduced (to the extent that the function of the battery is not impaired). By thinning to an acceptable range and increasing the number of stacked bicells instead, a large (unpredictable) output was obtained despite the same volume.

Examples of the present invention will be described below. The present invention is not limited in any way by this embodiment.
In the following, the best mode of the present invention will be described using an example of a non-aqueous electrolyte secondary battery.
The best mode of the present invention is a non-aqueous electrolyte type secondary battery using a positive electrode active material and a negative electrode material doped or dedoped with lithium, and an electrolyte layer (non-aqueous electrolyte or non-aqueous gel electrolyte).

[Polymer electrolyte lithium secondary battery]
The polymer electrolyte lithium secondary battery includes a positive electrode capable of occluding and releasing lithium ions, a negative electrode capable of occluding and releasing lithium ions, a polymer electrolyte containing a curable resin, a plasticizer and an electrolyte, and the following separator: Are provided.

[Separator]
A known secondary battery separator will be described as an example. The thermoplastic resin as the base resin of the thermoplastic resin composition constituting the separator is particularly preferably a polyolefin resin because of its excellent balance of heat resistance, solvent resistance and flexibility. Among the polyolefin resins, it is preferable to use polypropylene or polyethylene. As a filler contained in the thermoplastic resin composition constituting the separator, an inorganic filler having a property of not decomposing a non-aqueous electrolyte used in a lithium secondary battery is selected. The blending amount of the filler is preferably 20 to 30% by volume in the thermoplastic resin composition containing the thermoplastic resin and the filler. If the blending amount of the filler is extremely small, for example, less than 10% by volume, it is difficult to form a communication hole, and it becomes difficult to develop a function as a separator. Further, if the amount is extremely large, for example, exceeding 50% by volume, the viscosity at the time of film forming becomes high and the processability is inferior, and the film may be broken at the time of stretching for porous formation. If necessary, the thermoplastic resin composition may further contain other additives such as a low molecular weight compound and a heat stabilizer. The additive is not particularly limited as long as it is a known additive.

  The polyethylene microporous membrane is a known one, and has polyethylene as an essential component, and polyethylene is preferably the main matrix. As the polyethylene, one type or a plurality of polyethylenes can be used.

[Polymer electrolyte]
The electrolyte used has an electrolytic solution obtained by dissolving a lithium salt, which is usually a supporting electrolyte, in a non-aqueous solvent. The non-aqueous solvent is not particularly limited, but a relatively high dielectric constant solvent is preferably used. Specifically, cyclic carbonates such as ethylene carbonate and propylene carbonate, acyclic carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, glymes such as tetrahydrofuran, 2-methyltetrahydrofuran and dimethoxyethane, γ-butyllactone, etc. Lactones, sulfur compounds such as sulfolane, nitriles such as acetonitrile, and the like. Among them, it is preferable to use a high boiling point solvent having a boiling point of 150 ° C. or higher, particularly 200 ° C. or higher. Examples of such a high boiling point solvent include propylene carbonate, ethylene carbonate, butylene carbonate, and γ-butyrolactone. Among them, it is preferable to use propylene carbonate, ethylene carbonate, or γ-butyrolactone as a high boiling point solvent.

  The above non-aqueous solvent can use multiple types together. When the high boiling point solvent is used, the ratio of the high boiling point solvent to the non-aqueous solvent used is preferably 60% by volume or more, more preferably 70% by volume or more, more preferably 80% by volume or more, and most preferably 90%. Volume% or more.

The non-aqueous solvent preferably has a viscosity of 1 mPa · s or more.
The lithium salt is a supporting electrolyte used in the _{electrolyte, LiPF 6, LiAsF 6, LiSbF} 6, LiBF 4, LiClO 4, LiI, LiBr, LiCl, LiAlCl, L
Examples include iHF ₂ , LiSCN, LiSO ₃ CF _{2 and the} like. Of these, LiPF ₆ and LiClO ₄ are particularly preferred. The content of these supporting electrolytes in the electrolytic solution is usually 0.5 to 2.5 mol / l.

  The electrolyte is present as an electrolyte layer between the positive electrode and the negative electrode. In the present invention, the electrolyte of the electrolyte layer has a non-fluidity. As a result, even when the battery element is housed in a case having shape variability, the leakage of the electrolyte can be effectively prevented. As such a non-flowable electrolyte, specifically, a so-called polymer electrolyte in which the electrolytic solution is held by a polymer can be mentioned. The polymer electrolyte usually exhibits a gel state by holding the non-aqueous electrolyte with a polymer. The concentration of the polymer with respect to the electrolytic solution is usually 0.1 to 30% by weight, although it depends on the molecular weight of the polymer used. If the concentration is too low, it is difficult to form a gel, and the retention of the electrolytic solution is lowered, which may cause problems of flow and liquid leakage. On the other hand, when the concentration is too high, the viscosity becomes too high, resulting in difficulty in the process, and the ratio of the electrolytic solution is lowered, the ionic conductivity is lowered, and the battery characteristics such as the rate characteristics tend to be lowered. Various polymers having the above functions, such as an alkylene oxide polymer having an alkylene oxide unit and a fluorine polymer such as polyvinylidene fluoride or a vinylidene fluoride-hexafluoropropylene copolymer, can be used as a polymer for holding an electrolyte. Can be mentioned.

As a method of forming a non-fluidic electrolyte, a method of using it as an electrolyte coating in which a polymer is previously dissolved in an electrolytic solution, or a crosslinking reaction of an electrolytic coating containing a polymerizable monomer in the electrolytic solution to obtain a non-fluidic electrolyte. The electrolyte layer can be formed by adopting materials and manufacturing methods as required, such as methods.
In the case of forming the non-fluidic electrolyte in the present invention by a method in which a coating containing a polymerizable monomer in the electrolytic solution is subjected to a cross-linking reaction to obtain a non-fluidized electrolyte, a polymerization treatment such as ultraviolet curing or thermosetting is performed. A paint is prepared by adding a monomer that forms a polymer as a polymerizable monomer to the electrolyte.

  Examples of the polymerizable monomer include those having an unsaturated double bond such as an acryloyl group, a methacryloyl group, a vinyl group, and an allyl group. Specifically, for example, acrylic acid, methyl acrylate, ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate, ethoxyethyl methacrylate, methoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, polyethylene Examples include glycol monomethacrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, glycidyl acrylate, and allyl acrylate.

  Other usable examples include acrylonitrile, N-vinyl pyrrolidone, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene. Examples include glycol dimethacrylate, polyethylene glycol dimethacrylate, polyalkylene glycol diacrylate, and polyalkylene glycol dimethacrylate. Trifunctional monomers such as trimethylolpropane alkoxylate triacrylate and pentaerythritol alkoxylate triacrylate, pentaerythritol alkoxylate Tetraacrylate A tetrafunctional or higher functional monomer such as ditrimethylolpropane alkoxylate tetraacrylate can also be used. Of these, those preferable from the viewpoint of reactivity, polarity, safety, etc. may be used alone or in combination. Of these, diacrylates and triacrylates containing a plurality of ethylenoxide groups are particularly preferred. By polymerizing these monomers with heat, ultraviolet rays, electron beams or the like, the electrolyte can be made into a non-flowable electrolyte. The content of the polymerizable monomer in the electrolytic solution is not particularly limited, but is preferably 1% by weight or more in the paint. When the content is low, the formation efficiency of the polymer is lowered, and it is difficult to make the electrolyte non-fluid. On the other hand, if it is too much, residual unreacted monomer and operability as an electrolyte coating are deteriorated.

  In a method for producing a non-fluid electrolyte using an electrolyte coating containing a polymer in advance, it is preferable to use a polymer that dissolves in an electrolyte at a high temperature and forms a gel electrolyte at room temperature. Any polymer can be used as long as it has such characteristics and is stable as a battery material. For example, polymers having a ring such as polyvinyl pyridine and poly-N-vinyl pyrrolidone; polymethyl methacrylate, poly Acrylic derivative polymers such as ethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide; fluorinated resins such as polyvinyl fluoride and polyvinylidene fluoride; CN group-containing polymers such as acrylonitrile and polyvinylidene cyanide; polyvinyl alcohol polymers such as polyvinyl acetate and polyvinyl alcohol; halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride. Among these, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, or modified products thereof are preferable.

  Moreover, it can be used even if it is a mixture, such as said polymer, a modified body, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, etc. As will be described later, since the electrolyte and electrolyte used in the lithium battery have polarity, it is preferable that the polymer (polymer) has a certain degree of polarity. Furthermore, the weight average molecular weight of these polymers is preferably in the range of 10,000 to 5,000,000. If the molecular weight is low, it is difficult to form a gel. On the other hand, if the molecular weight is too high, the viscosity becomes too high and handling becomes difficult.

  In the method of forming a non-fluidized electrolyte using a polymer that dissolves in an electrolytic solution at a high temperature and forms a gel electrolyte at a normal temperature, the polymer is heated and dissolved in the electrolytic solution. As heating temperature, it is 50-200 degreeC, Preferably, it is 100-160 degreeC. If it seems to dissolve at too low a temperature, the stability of the non-fluidized electrolyte is reduced. If the melting temperature is too high, decomposition of the electrolyte component, polymer, etc. may be caused. As the non-fluidization condition, it is preferable to cool the polymer-dissolved electrolyte at room temperature, but it may be forcedly cooled.

  Various additives can be added to the electrolyte as needed to improve battery performance. The electrolyte layer is preferably used in combination with a support such as a porous film. As the porous film, a film made of a polymer resin or a thin film made of a powder and a binder can be preferably used, and more preferably a porous film made of polyethylene, polypropylene or the like.

[Positive electrode]
As the positive electrode, a material in which an active material layer containing a positive electrode active material and a binder is usually formed on a current collector is used. The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Preferable examples include lithium transition metal composite oxides.

Specific examples of lithium transition metal composite oxides include lithium / cobalt composite oxides such as LiCoO ₂ , lithium / nickel composite oxides such as LiNiO _2, and lithium / manganese composite oxides such as LiMnO ₂ and LiMn ₂ O _4. Is mentioned. In these lithium transition metal composite oxides, some of the main transition metal atoms are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, etc. Replacing with other metals is preferable because it can be stabilized. Any one of these positive electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.

  The binder is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used during electrode production and other materials used during battery use. Specific examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, EPDM (ethylene-propylene-diene terpolymer), SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), Examples thereof include fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, and nitrocellulose. These may be used individually by 1 type, or may use multiple types together.

  As for the ratio of the binder in the positive electrode active material layer, the lower limit is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and the upper limit is usually 80% by weight or less, preferably 60% by weight or less, more preferably 40% by weight or less, and still more preferably 10% by weight or less. If the proportion of the binder is small, the active material cannot be sufficiently retained, so that the mechanical strength of the positive electrode is insufficient, and the battery performance such as cycle characteristics may be deteriorated. On the contrary, if the amount is too large, the battery capacity and conductivity are lowered. It will be.

  The positive electrode active material layer usually contains a conductive agent in order to increase conductivity. Examples of the conductive agent include carbonaceous materials such as graphite fine particles such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon fine particles such as needle coke. These may be used individually by 1 type, or may use multiple types together.

  The ratio of the conductive agent in the positive electrode active material layer is such that the lower limit is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and the upper limit is usually 50% by weight or less. , Preferably 30% by weight or less, more preferably 15% by weight or less. If the proportion of the conductive agent is small, the conductivity may be insufficient, and conversely if too large, the battery capacity may be reduced.

  In addition, the positive electrode active material layer can contain additives for a normal active material layer such as a thickener. The thickener is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used during electrode production and other materials used during battery use.

  Aluminum or the like is used for the current collector of the positive electrode.

  The positive electrode can be formed by applying a slurry obtained by slurrying the above-described positive electrode active material, a binder, a conductive agent, and other additives added as necessary with a solvent onto a current collector, and drying the positive electrode active material. . As the solvent used for slurrying, an organic solvent that dissolves the binder is usually used. For example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like are used, but not limited thereto. These may be used individually by 1 type, or may use multiple types together.

  Thus, the thickness of the positive electrode active material layer formed is about 10-200 micrometers normally. The active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the active material.

[Negative electrode]
As the negative electrode, a material in which an active material layer containing a negative electrode active material and a binder is usually formed on a current collector is used.

  As a negative electrode active material, a carbonaceous material capable of occluding / releasing lithium such as organic pyrolysate, artificial graphite and natural graphite under various pyrolysis conditions; capable of occluding / releasing lithium such as tin oxide and silicon oxide Metal oxide material; lithium metal; various lithium alloys can be used. These negative electrode active materials may be used individually by 1 type, and may mix and use 2 or more types.

  The binder is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used during electrode production and other materials used during battery use. Specific examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, isoprene rubber, butadiene rubber and the like. These may be used individually by 1 type, or may use multiple types together.

  The ratio of the binder in the negative electrode active material layer is such that the lower limit is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and the upper limit is usually 80% by weight or less. Preferably it is 60 weight% or less, More preferably, it is 40 weight% or less, More preferably, it is 10 weight% or less. If the ratio of the binder is small, the active material cannot be sufficiently retained, so that the negative electrode mechanical strength may be insufficient, and the battery performance such as cycle characteristics may be deteriorated. become.

  In addition, the negative electrode active material layer may contain additives for a normal active material layer such as a thickener. The thickener is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used during electrode production and other materials used during battery use. Specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used individually by 1 type, or may use multiple types together.

  Copper, nickel, stainless steel, nickel-plated steel, or the like is used for the negative electrode current collector.

  The negative electrode can be formed by applying a slurry obtained by slurrying the above-described negative electrode active material, a binder, and other additives added as necessary with a solvent, and then drying the current collector. As the solvent used for slurrying, an organic solvent that dissolves the binder is usually used. For example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like are used, but not limited thereto. These may be used individually by 1 type, or may use multiple types together. Moreover, a dispersing agent, a thickener, etc. can be added to water, and an active material can also be slurried with latex, such as SBR.

  Thus, the thickness of the negative electrode active material layer formed is about 10-200 micrometers normally. The active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the active material.

[Battery configuration]
The polymer electrolyte lithium secondary battery of the present invention is produced by assembling the positive electrode, the negative electrode, and the separator described above into an appropriate shape and polymerizing them integrally with a polymer electrolyte. Furthermore, other components such as an outer case can be used as necessary. A preferable example of the battery shape is an aluminum laminate type in which a nylon layer, an aluminum foil, and a polypropylene layer are laminated. Moreover, the method for assembling the battery can be appropriately selected from various commonly used methods.

In the present invention, the unit battery element in which the positive electrode plate, the separator, and the negative electrode plate are laminated is configured in the same manner as the conventional unit battery element. For example, the positive electrode plate is formed by applying and drying the above-described positive electrode active material on one side of the reaction part of the positive electrode current collector, and the negative electrode plate is formed by applying and drying the negative electrode active material as described above on both sides of the reaction part of the negative electrode current collector. Thus, the separator can be exemplified by a polyolefin porous film. Further, a positive electrode current collector is formed on the positive electrode plate, and a negative electrode current collector is formed on the negative electrode plate, and these are joined to the positive electrode terminal lead and the negative electrode terminal lead by ultrasonic welding or the like. This joining may be performed by resistance welding. However, the unit cell element of the present invention is not limited to these.
As an embodiment of the battery of the present invention, a single cell composed of a positive electrode, a negative electrode, and a separator, which are plate-shaped unit battery elements, is laminated and assembled into a laminate type. A positive electrode active material containing an electrolyte and containing a negative electrode active material containing graphite on both sides of a copper foil negative electrode, and a positive electrode active material containing LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ on one side of an aluminum foil Unit batteries (bicells), in which two pairs of cathodes coated with a thickness of 54 μm are overlapped via a separator, are thinner than usual (generally used for camera-integrated VTRs, mobile phones, or portable computers) A laminated lithium secondary battery having a unit battery thickness of 7 layers or 8 layers.
The above-described negative electrode or positive electrode containing an electrolytic solution is performed by a method of impregnating an electrolytic solution that does not entrap air. The separator is placed on the negative electrode soaked with the electrolyte, the electrolyte is soaked, and the positive electrode soaked with the electrolyte is stacked thereon. The opposite is the same. Thereafter, they are integrated by thermal polymerization.

The thickness of the basic cell is [(number of stacked layers−natural number n] of a general battery used in a camera-integrated VTR, a mobile phone, or a portable computer (eg, a basic cell thickness of 314.0 μm is stacked in 6 layers). ) / Number of stacked layers] The basic cell thickness is doubled. The thickness of this basic cell will be described.
In the example, a laminated lithium secondary battery in which unit batteries (basic cell thickness is 268 μm) are stacked in 7 layers or unit batteries (basic cell thickness is 234 μm) is stacked in 8 layers was produced. However, the present invention is not limited to this, and 12 layers and 18 layers can be similarly manufactured.
That is, in the case of a multiple of 7, [(number of layers−factor of the number of layers other than 7 × 1) / number of layers]
In the case of 7 layers, natural number = 1 and thickness is 6/7
In the case of 14 layers, the natural number = 2 and the thickness is 6/7
In the case of 21 layers, the natural number is 3 and the thickness is 6/7.
In the case of a stack of multiples of 8, [(number of layers−factor of the number of layers other than 8 × 2) / number of layers]
In case of 8 layers, natural number = 2 and thickness is 6/8
In the case of 16 layers, the natural number is 4 and the thickness is 6/8.
In the case of 24 layers, natural number = 6 and thickness is 6/8
It is.

  The general embodiment of the polymer electrolyte lithium secondary battery of the present invention has been described above. However, the polymer electrolyte lithium secondary battery of the present invention is not limited to the above-described embodiment, and as long as it does not exceed the gist thereof. It is possible to implement various modifications.

  Hereinafter, details of the present invention will be described with reference to examples, but the present invention is not limited to the examples.

<Reference Example 1>
[(Number of stacked layers−integer n) / number of stacked layers] = 6/6 of the basic cell thickness [production of positive electrode stack]
As shown in FIG. 1, a positive electrode in which a positive electrode active material was applied to one side of an Al foil (aluminum foil) was produced.
The positive electrode active material LiNi _0.82 Co _0.15 Al _0.3 O ₂ (LNCAO) 64 wt% and LiCo ₂ O ₂ 25 wt%, and the conductive auxiliary agent acetylene black (AcB) 4 wt% are binders. 4% by weight of polyvinylidene fluoride (PVdF) was mixed in N-methylpyrrolidone (NMP) as a solvent to prepare a positive electrode mixture slurry. The obtained slurry was applied to a current collector (positive electrode support) made of an Al foil having a thickness of 20 μm, dried and pressed to form a positive electrode active material layer having a thickness of 54 μm on the current collector.

[Preparation of negative electrode laminate]
As shown in FIG. 1, one set of negative electrodes was prepared by applying a negative electrode active material containing graphite on both sides of a negative electrode of a Cu foil (copper foil). N-methylpyrrolidone (NMP) as a solvent containing 77% by weight of graphite as a negative electrode active material, 15% by weight of mesocarbon microbeads (MCMB) as a conductive agent, and 8% by weight of polyvinylidene fluoride (PVdF) as a binder The mixture was mixed in a negative electrode mixture slurry. The obtained slurry is applied onto a current collector (negative electrode support) made of 12 μm thick Cu foil, dried, and then pressed to form a negative electrode active material layer having a thickness of 62 μm on the current collector. did.

[Preparation of electrolyte]
An electrolyte paint (pre-curing electrolyte composition) in which a polymerizable monomer was contained in the electrolytic solution was prepared.
The electrolyte paint comprises ethylene carbonate (EC) / propylene carbonate (PC) = 1/1 (Vol / Vol) as a solvent, tetraethylene glycol diacrylate and ethylene oxide-modified trimethylpropane acrylate as a polymerizable monomer, and a polymerization initiator. the mixed solution, LiPF ₆ is a solution obtained by dissolving at a concentration of 1.3 mol / L.

[Production of lithium secondary battery]
A 16 μm thick Tonen (length 63 mm × width 68 mm, registered trade name: SETELA E16MMS, manufactured by Tonen Functional Membrane Godo Kaisha), which is a battery separator made of polyethylene resin, was used.
Air is prevented from entering on both surfaces of a negative electrode (61 mm long × 64 mm wide double-sided electrode) coated with a negative electrode active material containing graphite on both sides of the negative electrode of Cu foil (copper foil) produced as described above. After applying the electrolyte coating to the separator, the separator was placed and impregnated with the electrolyte, and then a positive electrode (60 mm long × 60 mm long) coated with a positive electrode active material on one side of the Al foil (aluminum foil) produced as described above. Two sets of electrode materials are applied so that air does not enter the horizontal 63 mm single-sided electrode) and the active material layer is impregnated with the electrolyte. The two sets are overlapped through the separator and heated at 90 ° C. for 5 minutes. The electrolyte coating is cross-linked to form a non-fluidic electrolyte, positive electrode / positive electrode active material layer / separator / negative electrode active material layer / negative electrode, more specifically, positive electrode / positive electrode active material layer / polymer gel electrolyte / separator / high Molecular gel electrolysis A unit battery (bicell) having a unit of negative electrode active material layer / negative electrode / negative electrode active material layer / polymer gel electrolyte / separator / polymer gel electrolyte / positive electrode active material layer / positive electrode in a thickness of 314.0 μm Formed (see FIG. 2), and the unit cells were stacked in six layers. And the outer periphery of the laminated body laminated | stacked was covered with the exterior material, and the lithium secondary battery was produced. In the lithium secondary battery, a terminal can be taken from the current collector of each laminate (see FIG. 3).
The thickness of 314.0 μm is the thickness of a basic cell of a general battery used for a camera-integrated VTR, a mobile phone, or a portable computer.

<Example 1>
[(Number of stacked layers−natural number n) / number of stacked layers] = 6/7 of the basic cell thickness In Example 1, the lithium secondary battery of Reference Example 1 is an Al foil constituting the positive electrode stack. The thickness was changed to 17 μm, the thickness of the positive electrode active material layer was changed to 46 μm, the thickness of the Cu foil constituting the negative electrode laminate was changed to 10 μm, and the thickness of the negative electrode active material layer was changed to 53 μm. The unit battery (bi-cell) that was stacked using a thickness was formed to a thickness of 268 μm, and the composition of the layers other than stacking the unit battery into 7 layers, the formation method of each layer, etc. are reference examples. Same as 1.

<Example 2>
[(Number of stacked layers−natural number n) / number of stacked layers] = 6/8 of the basic cell thickness In Example 2, the lithium secondary battery of Reference Example 1 is the Al foil constituting the positive electrode stack. As the separator, the thickness was changed to 15 μm, the thickness of the positive electrode active material layer was changed to 40.5 μm, the thickness of the Cu foil constituting the negative electrode laminate was changed to 8 μm, and the thickness of the negative electrode active material layer was changed to 46.5 μm. A unit cell (bicell) with a thickness of 11 μm is used to form a unit cell (bicell) with a thickness of 234 μm, and the composition of the layers other than stacking the unit cell in 8 layers, the formation method of each layer, etc. are for reference Same as Example 1.

<Test example>
(Evaluation of battery characteristics with respect to basic cell thickness)
Using the lithium secondary batteries of Examples 1 and 2 and Reference Example 1 described above, the battery output density of each battery was measured, and the output density of each battery was evaluated. A unit battery (bi-cell) with a thickness of 314 μm × 6 layer battery (Reference Example 1) to be compared is a general battery used for a camera-integrated VTR, a mobile phone, or a portable computer.
The thicknesses of the basic cells of Examples 1 and 2 with respect to Reference Example 1 were changed to 6/7 and 6/8, and each thickness was measured under the condition of 10 seconds of output from SOC 50% to the lower limit voltage 2.5 V. The battery characteristics with respect to the thickness of the basic cell were evaluated by measuring the battery output density. The internal temperature of the battery at the time of measuring the battery output density was constant at 20 ° C.

  As shown in FIG. 6, the bicell thickness ratio 6/8 shows a power density that is about 4.3 times that of 6/6, and is expected from a simple increase in the number of stacked layers. / 6 is significantly higher than 1.33 times. The same applies to the bicell thickness ratio of 7/8, and it was revealed that the battery characteristics were further improved.

The invention of the present application is to manufacture a general battery used in a conventional camera-integrated VTR, a mobile phone, or a portable computer, and to produce a high output battery with almost no manufacturing change or material change. Since the conventional production line can be used as it is, it is possible to deal with mass production at low cost.
In particular, the lithium battery of the present invention can be suitably used for a lithium secondary battery for a hybrid vehicle that is required to have a high output density for supplying a large amount of power in a short time.

It is a longitudinal cross-sectional view for demonstrating the state before the assembly of the basic cell of the general battery used for camera integrated VTR, a mobile telephone, or a portable computer in a polymer electrolyte lithium secondary battery. It is a longitudinal cross-sectional view of the battery basic cell after the assembly of FIG. It is a longitudinal cross-sectional view of the lithium secondary battery produced by stacking 6 layers of the battery basic cell of FIG. 2 is a longitudinal sectional view of a battery basic cell of Example 1. FIG. It is a longitudinal cross-sectional view of the lithium secondary battery produced by laminating | stacking seven battery basic cells of Example 1. FIG. It is drawing which shows the result of having evaluated the output density of the lithium secondary battery of Example 1 (6/7), Example 2 (6/8), and Reference Example 1 (6/6).

Claims (12)

  In a polymer electrolyte laminated lithium secondary battery, each layer (positive electrode / positive electrode active material layer / separator / negative electrode active material layer / negative electrode) constituting a unit battery is sequentially laminated to form a camera-integrated VTR, a mobile phone, or a portable computer. A polymer electrolyte laminated lithium secondary battery with improved output performance, characterized in that the thickness of the basic cell is [(number of stacked layers−natural number n) / number of stacked layers] times that of a general battery used in a battery.   A pair of double-sided negative electrodes in which a negative electrode active material slurry is directly applied to both sides of a negative electrode current collector, each of which is preliminarily impregnated with an electrolyte containing a monomer, a separator that is impregnated with the electrolyte, and A unit cell having a bi-cell structure in which a positive electrode in which an anode active material slurry is directly applied to one side of an anode current collector, and two sets each impregnated with the electrolytic solution are sequentially stacked and then thermally polymerized to be integrated. The polymer electrolyte laminated lithium secondary battery according to claim 1. The positive electrode is a positive electrode in which a positive electrode active material containing LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ is applied to one side of an aluminum foil, and one negative electrode is applied to a negative electrode active material containing graphite on both sides of the negative electrode of a copper foil The polymer electrolyte laminated lithium secondary battery according to claim 1, wherein the negative electrode is a set of negative electrodes.   4. The polymer electrolyte laminated lithium secondary battery according to claim 1, wherein the (number of laminated layers−natural number n) is a multiple of 6. 5.   The polymer electrolyte laminate according to any one of claims 1 to 3, wherein the number of laminations is a multiple of 7, and the thickness of the basic cell [(number of laminations-number of laminations / 7) / number of laminations) times is 268 µm. Lithium secondary battery.   The polymer according to any one of claims 1 to 3, wherein the number of layers is a multiple of 8, and the thickness of a basic cell of [(number of layers−number of layers × 2/8) / number of layers] is 234 μm. Electrolyte laminated lithium secondary battery.   In a polymer electrolyte laminated lithium secondary battery, each layer (positive electrode / positive electrode active material layer / separator / negative electrode active material layer / negative electrode) constituting a unit battery is sequentially laminated to form a camera-integrated VTR, a mobile phone, or a portable computer. A method of improving the output performance of a polymer electrolyte laminated lithium secondary battery, characterized in that the thickness of the basic cell is [(number of stacked layers−natural number n) / number of stacked layers] times that of a general battery used in the above.   A pair of double-sided negative electrodes in which a negative electrode active material slurry is directly applied to both sides of a negative electrode current collector, each of which is preliminarily impregnated with an electrolyte containing a monomer, a separator that is impregnated with the electrolyte, and A positive electrode in which an anode active material slurry is directly applied to one side of an anode current collector, in which two sets each impregnated with the electrolytic solution are sequentially laminated, and then thermally polymerized to form a united bicell structure The method for improving the output performance of the polymer electrolyte laminated lithium secondary battery according to claim 7, wherein the battery is a battery. The positive electrode is a positive electrode in which a positive electrode active material containing LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ is applied to one side of an aluminum foil, the negative electrode includes an electrolyte solution, and the negative electrode includes graphite on both sides of the negative electrode of the copper foil The method for improving the output performance of the polymer electrolyte laminated lithium secondary battery according to claim 7, wherein the negative electrode is coated with an active material.   The method for improving the output performance of the polymer electrolyte laminated lithium secondary battery according to claim 7, wherein the (number of laminated layers−natural number n) is a multiple of 6. 10.   10. The polymer electrolyte multilayer lithium battery according to claim 7, wherein the number of stacked layers is a multiple of 7 and the thickness of a basic cell of [(number of stacked layers−natural number n) / number of stacked layers] is 268 μm. A method to improve the output performance of secondary batteries.   10. The polymer electrolyte multilayer lithium battery according to claim 7, wherein the number of stacked layers is a multiple of 8 and the thickness of a basic cell of [(number of stacked layers−natural number n) / number of stacked layers] is 234 μm. A method to improve the output performance of secondary batteries.