JPH08222272A - Combination battery of nonaqueous electrolyte secondary battery and solar battery - Google Patents

Abstract

PURPOSE: To provide a combination battery of an overdischarging preventive lithium nonaqueous electrolyte secondary battery and a solar battery, and an overdischarging preventive nonaqueous electrolyte lithium secondary battery which is suitable for use in this combination battery. CONSTITUTION: A nonaqueous electrolyte secondary battery composed of a layered structural body of at least a positive electrode current collecting body layer, a positive electrode active material layer, an electrolyte layer, a carbon negative electrode active material layer and a negative electrode current collecting body layer and a solar battery are comined with each other. At least the negative electrode current collecting body layer of a nonaqueous electrolyte secondary battery is composed of stainless steel.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a combination battery of a non-aqueous electrolyte secondary battery and a solar cell, and a non-aqueous electrolyte secondary battery used for the combination battery.

[0002]

2. Description of the Related Art Recent advances in miniaturization, thinning, and weight reduction of electronic devices have been remarkable, and in the OA field, in particular, desktop devices have been reduced in size and weight to laptop types and notebook types. In addition, the field of new small electronic devices such as electronic notebooks and electronic still cameras has also appeared, and in addition to the miniaturization of conventional hard disks and floppy disks, the development of memory cards, which are new memory media, is under way. In the wave of miniaturization, thinning, and weight reduction of such electronic devices, high performance is also required for secondary batteries that support such electric power.
In such a demand, development of a lithium non-aqueous electrolyte secondary battery has been rapidly advanced as a high energy density battery which replaces a lead storage battery or a nickel cadmium battery. In particular, thin batteries called paper batteries, thin flat batteries, or plate-like batteries have been developed in recent years for the purpose of reducing the thickness. Examples of positive electrode active materials for lithium non-aqueous electrolyte secondary batteries include TiS ₂ , MoS ₂ , CoO ₂ , V ₂ O ₅ , FeS ₂ , and N.
Many examples of transition metal oxides such as bS ₂ , ZrS ₂ , and MnO ₂ or transition metal chalcogen compounds, in which an inorganic material is used as an active material, have been studied. Such a material is capable of electrochemically reversibly taking lithium ions in and out of its structure, and by utilizing this property, development of a lithium non-aqueous electrolyte secondary battery has been advanced. Since a lithium non-aqueous electrolyte secondary battery using such an inorganic material as an active material generally has a high true density of the active material itself, it is easy to configure a battery having a high energy density, and lithium absorption and desorption is the active material. In the case of intercalation or deintercalation in the crystal structure, it is easy to form a battery having excellent voltage flatness. On the other hand, if more lithium ions are accumulated in the crystal structure,
It has a drawback that the crystal structure is destroyed and the function as an active material of the non-aqueous electrolyte secondary battery is significantly reduced. This means that the electrode for a non-aqueous electrolyte secondary battery is vulnerable to overdischarge. In the process of developing a lithium non-aqueous electrolyte secondary battery using such an inorganic material as an active material, the anion is reversibly occluded as a potential electrode active material of the lithium non-aqueous electrolyte secondary battery in recent years. However, there was a discovery of a conductive polymer that can perform an electrode reaction by releasing it.
The conductive polymer is lightweight as an electrode material and has characteristics such as high output density, and also has excellent current collecting properties due to the conductivity, which is a unique property of the material, and exhibits high cycle characteristics even at a discharge depth of 100%. In addition, it has characteristics that inorganic materials do not have, such as good moldability as an electrode. As an example of the conductive polymer, polyacetylene (for example, JP-A-56)
-136489), polypyrrole (for example, 25th Battery Symposium, Lecture Summary, P2561, 1984), polyaniline (for example, Electrochemical Society 50th Convention, Lecture Summary, P2281, 1984) and the like. .
The lithium non-aqueous electrolyte secondary battery has a technical problem of developing a negative electrode in addition to the above-described development of the positive electrode. Conventionally, lithium and lithium aluminum alloys have been used for the negative electrode of lithium non-aqueous electrolyte secondary batteries, but lithium has the drawbacks of poor charging / discharging cycle characteristics and the risk of short circuit due to dendrites. Despite the fact that the cycle characteristics can be secured to some extent, it has the drawbacks that it is difficult to make a high-voltage battery and it is not flexible because the potential of the material moves in a noble direction. Therefore, recently, a lithium non-aqueous electrolyte secondary battery using a carbon material capable of occluding and releasing lithium as a negative electrode has attracted attention and has been actively researched and developed. This battery is called a lithium ion battery. As described above, the main technical issue in the development of lithium-ion batteries that meet the demands for battery size reduction and weight reduction is the development of positive and negative electrodes, but the current collectors for fixing these active materials are also positive and negative. It changes according to the change in the function of the active material. That is, it is desired that the current collector is thinner, has a material that does not chemically or electrochemically react, has high mechanical strength, and has good adhesion to the active material. Further, the development of a solar cell has been advanced as a means for supporting the electric power of the high energy density battery such as the lead storage battery, the nickel-cadmium battery and the lithium battery. However, the solar cell is not a storage battery, but is a so-called power generator that supplies electric power only when there is light, and the supply of electric power also stops if the light disappears. Therefore, there is an idea to use a device while using a solar battery and a secondary battery together and accumulating the electric power generated by the solar battery in the secondary battery. In this method, the secondary battery needs to be resistant to overdischarge. Generally, between the solar cell and the secondary battery, a circuit element for holding the charging voltage and the charging current at a certain level and a diode for preventing the reverse flow of current from the secondary battery to the solar cell are connected. It is used when the solar cell is exposed to light and power is supplied, but when the light is blocked,
A phenomenon occurs in which a minute reverse current flows from the secondary battery to the solar cell according to the internal resistance of the diode and the internal resistance of the solar cell during reverse current flow. This is a small amount of current, but when the device is placed in an environment where the solar cell does not function normally for a long period of time, the secondary battery continues to flow a minute current and eventually becomes over-discharged. If the secondary battery used at this time is vulnerable to over-discharging, the function of the secondary battery will be significantly reduced (reduced capacity) or unusable (power will not be reduced) even if the solar cell is normally exposed to light. Cannot be stored). The secondary battery generally includes a nickel cadmium battery, a nickel hydrogen battery, a lead battery, a lithium battery, a lithium ion battery and the like. Conventionally, NiCd batteries and NiMH batteries have been used in combination with solar cells. This is because these batteries are resistant to over discharge. Lithium batteries and lithium-ion batteries are batteries that have been actively researched in recent years as batteries having a high energy capacity 1.5 to 2 times that of nickel-cadmium batteries and nickel-hydrogen batteries, but they are vulnerable to over-discharge and are called solar cells. Was not suitable for the combination of. In addition, a lithium battery (using lithium metal) has been ignited in some cases, and its safety is greatly questioned. A battery that solves this safety problem by replacing the lithium metal of the negative electrode with a carbon material is a lithium ion battery, but the problem of being weak against over-discharge has not been solved.

[0003]

An object of the present invention is to provide a combination battery of a lithium non-aqueous electrolyte secondary battery resistant to over-discharge and a solar cell, and a non-aqueous electrolyte lithium secondary battery resistant to over-discharge suitable for use in the combination battery. It is to provide batteries.

[0004]

[Constitution] Conventionally, copper has been generally used as a current collector of a lithium ion battery. Copper is a cheap metal, has a high electric conductivity, and is stable on the base potential side, and was a preferable current collector when handling a carbon-based negative electrode. However, a conventional battery using copper as a current collector for a carbon material-based negative electrode active material has a drawback in that copper is eluted when it is in an overdischarged state, resulting in significant deterioration of battery performance. A battery using a carbon material-based active material for a negative electrode differs from a battery using a conventional Li metal for a negative electrode in that the potential of the negative electrode greatly changes similarly to that of the positive electrode, and the potential of the carbon negative electrode and the potential of the positive electrode at that time are different from each other. The difference between the two appears as a voltage. 1 to 3 are conceptual diagrams of potential changes during discharge of a conventional positive electrode and carbon-based negative electrode. As shown in FIG. 1, the potential change associated with the discharge of the positive electrode usually proceeds while maintaining a substantially constant potential, and when the active material becomes difficult to receive electrons, the potential suddenly decreases. It is common. As shown in FIG. 2, the potential change accompanying the discharge of the carbon negative electrode usually rises rapidly when the discharge progresses while maintaining a substantially constant potential and the active material hardly emits electrons. Is common. The combination of these positive and carbon negative potential changes is the battery voltage,
The portion 3 in FIG. 3 will appear as a voltage. Here, in the conventional carbon battery, as shown in FIG. 3, the discharge progresses, and the potential of the negative electrode rises at the position where the voltage becomes 0 V (overdischarge), and the potential of the positive electrode hardly changes. (Point A). This is because the number of electrons that can be emitted from the negative electrode is set to be smaller than the number of electrons that can be received by the positive electrode active material of the conventional carbon battery. Is a phenomenon that occurs because a large amount of is contained. At this time, for example, when copper is used as the current collector of the carbon-based negative electrode active material, the increase in the potential of the negative electrode becomes more noble than the oxidation-reduction potential of copper, resulting in the elution of copper and deterioration of battery performance. As a result, phenomena such as short circuit, heat generation, and ignition due to copper dissolution and precipitation will occur. When such a secondary battery is combined with a solar cell, a small reverse current corresponding to the internal resistance of the diode during reverse current and the internal resistance of the solar cell causes the secondary battery to overdischarge as described above. Therefore, it is obvious that the function of the secondary battery is significantly deteriorated. The present invention has been studied based on the above findings, and as described above, at least the positive electrode current collector layer 1, the positive electrode active material layer 2, the electrolyte layer 3, the carbon-based negative electrode active material layer 4, and It has been found that the above-mentioned drawbacks can be overcome by using at least the negative electrode current collector layer 5 made of stainless steel in the combined battery of the secondary battery and the solar cell having the laminated structure of the negative electrode current collector layer 5. That is, stainless steel is electrochemically stable even at a higher potential than copper, and by using a negative electrode current collector of stainless steel, a battery in which the negative electrode current collector does not elute even during overdischarge is manufactured. be able to. As the stainless steel used in the present invention, among the many stainless steels, those which are chemically and electrochemically stable are preferably used.

The positive electrode active material used in the battery of the present invention is TiS ₂ , MoS ₂ , Co ₂ S ₅ , V ₂ O ₅ , MnO ₂ ,
Transition metal oxides such as CoO _{2 and the} like, transition metal chalcogen compounds and complexes thereof with Li (Li complex oxide; Li
MnO ₂ , LiMn ₂ O ₄ , LiCoO _2, etc.), a one-dimensional graphitized product of a thermal polymer of an organic substance, carbon fluoride, graphite, or a conductive polymer having an electric conductivity of 10 ⁻² S / cm or more, Specific examples thereof include polymers such as polyaniline, polypyrrole, polyazulene, polyphenylene, polyacetylene, polyacene, polyphthalocyanine, poly-3-methylthiophene, polypyridine, and polydiphenylbenzidine, and derivatives thereof, but at a discharge depth of 100%. On the other hand, it is preferable to use a conductive polymer that exhibits high cycle characteristics and is relatively resistant to overdischarge as compared with an inorganic material. In addition, the conductive polymer is
Since it is a plastic in terms of moldability and processability, it can take advantage of features that were not available in the past. Although the conductive polymer has the above advantages, the nonaqueous electrolyte secondary battery using the conductive polymer as the positive electrode has a low volume energy density due to the low density of the active material, and Since the electrolyte needs an electrolyte sufficient for the electrode reaction and the concentration of the electrolyte changes greatly with the charge / discharge reaction, the change in the liquid resistance is large, and a smooth charge / discharge reaction is required. However, there is a problem that an excessive amount of electrolytic solution is required. This is a disadvantage in improving the energy density. On the other hand, as the active material having a high volume energy density, the inorganic chalcogenide compound and the inorganic oxide may be used for the positive electrode, but the inorganic chalcogenide compound and the inorganic oxide are active materials having a high volume energy density. However, these have the problems that the diffusion rate of cations in the electrode is slow due to the electrode reaction associated with charging / discharging, rapid charging / discharging is difficult, reversibility is poor with respect to overdischarge, and the cycle life is reduced. Moreover, since it is difficult to mold the inorganic active material as it is, pressure molding is often performed using a tetrafluoroethylene resin powder or the like as a binder, but in that case, the mechanical strength of the electrode is not sufficient. In addition, when over-discharging, when lithium ions are excessively accumulated, the crystal structure is destroyed and the non-aqueous electrolyte secondary battery does not function.

In order to solve such problems of organic and inorganic active materials, it is possible to use organic and inorganic composite active materials. In this case, any of the polymer active materials used is required to have high electrical conductivity by electrochemical doping, and the electrode material is required to have electrical conductivity of 10 ⁻² S / cm or more. Also, high ionic conductivity is required in terms of diffusivity of ions. These polymer materials have a high electric conductivity and a current collecting ability,
It has a binding ability as a polymer and also functions as an active material. In addition, since the conductive polymer is insulated at a base potential, even when this composite positive electrode is in an overdischarged state, the conductive polymer is insulated so that the inorganic active material contained therein contains more lithium ions than necessary. It prevents the accumulation and the destruction of the crystal structure of the inorganic active material. As a result, it is possible to construct an electrode that is substantially resistant to over-discharge. As described above, the conductive polymer used for the composite positive electrode is a material that has the ability as an active material, does not dissolve in an electrolytic solution, has a binding property between polymer materials, and exhibits conductivity. The inorganic active material is fixed as a binder. At this time,
The inorganic active material is entirely incorporated in the conductive polymer, and as a result, the entire circumference of the inorganic active material becomes conductive. Examples of such a conductive polymer include redox active materials such as polyacetylene, polypyrrole, polythiophene, polyaniline, and polydiphenylbenzidine. Particularly, a nitrogen-containing compound is particularly effective. These conductive polymer materials are required to have high ionic conductivity in terms of not only conductivity but also diffusion of ions. Among these, polypyrrole, polyaniline, and their copolymers are preferable because they have a relatively large electric capacity per weight and can be charged and discharged relatively stably in a general-purpose non-aqueous electrolyte. More preferred is polyaniline. The inorganic active material used for the composite positive electrode is preferably one having excellent potential flatness, and specifically, an oxide of a transition metal such as V, Co, Mn, or Ni or a composite oxide of the transition metal and an alkali metal is exemplified. The crystalline vanadium oxide is preferable, and vanadium pentoxide is particularly preferable, in consideration of stable electrode potential, voltage flatness, and energy density in the electrolytic solution. The reason is that the potential flat portion of the discharge curve of crystalline vanadium pentoxide is relatively close to the electrode potential due to the insertion and desorption of the anion of the conductive polymer.

A carbonaceous material is used as the negative electrode material used in the battery of the present invention. Examples of the carbonaceous negative electrode active material include graphite, pitch coke, synthetic polymer, and a sintered body of natural polymer. In the present invention, synthetic polymer such as phenol and polyimide, or natural polymer is used.
Conductivity obtained by firing an insulating or semiconducting carbon body, coal, pitch, synthetic polymer or natural polymer obtained by firing in a reducing atmosphere at 800 to 1300 ° C. in a reducing atmosphere at 800 to 1300 ° C. Carbon body,
2000 for coke, pitch, synthetic polymer, natural polymer
What is obtained by firing in a reducing atmosphere at a temperature of ℃ or more, and a graphite-based carbon body such as natural graphite is used, but a carbon body is preferable. Among them, mesophase pitch and coke are fired in a reducing atmosphere of 2,500 ° C or more. The resulting carbon body and natural graphite have excellent potential flatness and have favorable electrode characteristics. In a further preferred embodiment of the present invention, coke is 2500 ° C.
This is to use the composite negative electrode of the carbon body and natural graphite which is fired in the above reducing atmosphere. Although natural graphite has preferable characteristics in terms of potential flatness and current characteristics, it has a problem of decomposing propylene carbonate, which is a solvent of a general-purpose electrolytic solution that has been conventionally used in non-aqueous electrolytic solution secondary batteries. Further, the carbon body obtained by firing the coke in a reducing atmosphere at 2500 ° C. or higher does not have the above-mentioned problems and is characterized in that the electrolytic solution can be easily selected. On the other hand, by using a composite of a carbon body obtained by firing coke in a reducing atmosphere at 2500 ° C. or higher and natural graphite as a negative electrode, the potential flatness and current characteristics of natural graphite are retained, and A negative electrode that does not decompose the liquid can be produced. The carbon body is formed into a sheet by a wet papermaking method using the carbon body and a binder, or by a coating method using a coating material in which a suitable binder is mixed with a carbon material. The electrode can be manufactured by supporting the electrode on a current collector by a method such as coating, adhesion, and pressure bonding, if necessary.

Examples of the positive electrode current collector used in the present invention include metal sheets such as stainless steel, gold, platinum, nickel, aluminum, molybdenum, and titanium, metal foils, metal nets, punching metals, expanded metals, or metals. Examples include nets and non-woven fabrics made of plated fibers, metal vapor deposition wires, metal-containing synthetic fibers and the like. Of these, aluminum and stainless steel are particularly preferable in consideration of electrical conductivity, chemical stability, electrochemical stability, economic efficiency and workability. Aluminum is more preferable because of its lightness and electrochemical stability. The surfaces of the positive electrode current collector layer and the negative electrode current collector layer used in the present invention are preferably roughened. By roughening, the contact area of the active material layer is increased, and the adhesion is also improved, which has the effect of lowering the impedance of the battery. Further, in the production of an electrode using a coating solution, it is possible to greatly improve the adhesion between the active material and the current collector by subjecting it to a surface roughening treatment. The roughening treatment includes polishing with emery paper, blasting treatment, and chemical or electrochemical etching, whereby the current collector can be roughened. Particularly, in the case of stainless steel, etched aluminum is preferable, and in the case of aluminum, etched aluminum is preferable. Since aluminum is a soft metal, the blasting process cannot be effectively roughened and the aluminum itself will be deformed. On the other hand, the etching treatment can effectively roughen the surface on a microscopic order without significantly deforming the aluminum or significantly reducing its strength, and is the most preferable method for roughening the aluminum.

An organic non-aqueous polar solvent is used as the electrolytic solution used in the non-aqueous electrolytic solution secondary battery of the present invention, and it is preferable that the organic non-aqueous polar solvent is aprotic and has a high dielectric constant. Specific examples thereof include propylene carbonate, ethylene carbonate, γ-butyl lactone,
Examples thereof include, but are not limited to, dimethyl sulfoxide, dimethylformamide, dimethoxyethane, dimethyl carbonate, and diethyl carbonate. The organic non-aqueous polar solvent may be used alone or in combination of two or more. In a further preferred embodiment of the present invention, it is preferable to use a mixed electrolytic solution of propylene carbonate, ethylene carbonate and dimethyl carbonate. By using this combination, it is possible to suppress the self-discharge of the positive and negative electrodes and improve the cycle characteristics. Further, although the low temperature coagulation of ethylene carbonate has conventionally determined the low temperature characteristics of the battery, by mixing propylene carbonate and dimethyl carbonate, which are carbonate-based materials like ethylene carbonate, it is possible to prevent the coagulation of the solvent due to the low temperature of the battery. The low temperature characteristics can be improved. The electrolyte concentration cannot be unconditionally specified because it varies depending on the positive electrode used, the electrolyte and the type of the organic non-aqueous polar solvent, etc., but is usually in the range of 0.1 to 10 mol / liter.

The kind of the electrolyte salt used in the present invention is not particularly limited, but one that is dissolved in a non-aqueous solvent and exhibits high ionic conductivity is used. Examples of such substances include alkali metal ions as cations and Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , Cl as anions.
O ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ , (C
F ₃ SO ₂ ) ₂ N ^{− and the} like can be exemplified. Among the above-mentioned electrolyte salts, LiN (CF ₃ SO ₂ ) ₂ has a high ionic conductivity and good matching with a composite positive electrode and a composite negative electrode, specifically, cycle characteristics, load characteristics, and low temperature characteristics. Therefore, it is preferable as an electrolyte salt for non-aqueous electrolyte secondary batteries. However, LiN
(CF ₃ SO ₂ ) ₂ is corrosive, and particularly when the positive electrode current collector layer is aluminum, the corrosion is remarkable. The corrosiveness means that an elution current of aluminum flows when an electric field is applied. As a result of studying to suppress the corrosiveness, the present inventors have found that LiN (CF ₃ SO ₂ ) ₂ contains another electrolyte. Corrosion could be suppressed by adding salt. As the above-mentioned other electrolyte salt, the addition of an electrolyte salt composed of a combination of the above-mentioned cation and anion was effective, but LiBF ₄ was added in view of prevention of corrosion and matching with the composite positive electrode and composite negative electrode of the present invention. It is preferable. That is, a preferred embodiment of the present invention is to use a mixed electrolyte of LiN (CF ₃ SO ₂ ) ₂ and another electrolyte salt as the electrolyte salt, and examples of the other electrolyte salt include LiBF _4. More preferably, by using BF ₄ as an anion as the other electrolyte salt and using an alkali metal or alkaline earth metal ion other than lithium metal or a tetraalkylammonium ion as the cation in combination, a particularly remarkable effect is obtained. It turned out to represent. As the electrolyte, a solid electrolyte is preferable because it has no leakage and is highly safe when the battery heats up. As the solid electrolyte used in the present invention, for example, in an inorganic system, AgCl, AgBr, AgI, LiI
Metal halides such as RbAg ₄ I ₅ , RbAg ₄ I ₄
A CN ion conductor etc. are mentioned. In organic systems, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylonitrile, etc. are used as a polymer matrix to dissolve an electrolyte salt, or a cross-linked product, low molecular weight polyethylene oxide, polyethyleneimine, crown ether, etc. The polymer solid electrolyte in which the ion dissociative group of is grafted to the polymer main chain can be mentioned. Alternatively, a gelled polymer solid electrolyte having a structure in which the high molecular weight polymer contains the electrolytic solution is used. The gelled polymer solid electrolyte is a solid electrolyte that is obtained by adding a polymerizable compound to an ordinary electrolytic solution and polymerizing the compound by heat or light. More specifically, those described in WO91 / 14294 are used.
As an polymerizable compound, an acrylate compound (eg, methoxydiethyl glycol methacrylate, methoxydiethylene glycol diacrylate) is polymerized by using a polymerization initiator such as benzoyl peroxide, azobisisobutyronitrile, methylbenzoyl formate, benzoin isopropyl ether, and electrolysis. This is to solidify the liquid. Among such solid electrolytes, it is preferable to use a gel polymer solid electrolyte from the viewpoint of ionic conductivity and flexibility. The electrolyte salt used for the gelled solid electrolyte is not particularly limited, but those which dissolve in a non-aqueous solvent and exhibit high ionic conductivity are used. An example of such a substance is an alkali metal ion as the cation. Examples of anions include Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , ClO ₄ ⁻ , B.
F ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ S
O ₂ ) ₂ N ⁻ can be exemplified. Although an organic non-aqueous polar solvent is used as the electrolytic solution, an organic non-aqueous polar solvent that is aprotic and has a high dielectric constant is preferable. Specific examples thereof include propylene carbonate, γ-butyl lactone, dimethyl sulfoxide, dimethylformamide, ethylene carbonate, dimethoxyethane, dimethyl carbonate and diethyl carbonate. The organic non-aqueous polar solvent may be used alone or in combination of two or more. Preferred is a mixed solvent of solvents selected from the group consisting of propylene carbonate, ethylene carbonate and dimethyl carbonate. The electrolyte concentration cannot be unconditionally specified because it varies depending on the type of positive electrode, electrolyte and organic non-aqueous polar solvent used, but it is usually 0.1-10.
It is preferably in the range of mol / liter.

A separator may be used in the battery of the present invention. As the separator, it is preferable to use a separator that has a low resistance to the movement of ions of the electrolyte solution and is excellent in retaining the solution. Examples of such a separator include a glass fiber, a filter, a non-woven fabric filter made of polymer fibers such as polyester, Teflon, polyflon, and polypropylene, and a non-woven fabric filter made by mixing glass fibers and these polymer fibers. The solar cell used in the present invention is not particularly limited as long as it exhibits a power generation function by light, and more specifically, an inorganic semiconductor solar cell such as crystalline silicon, polycrystalline silicon, or amorphous silicon is generally used. Used. Further, in general, a solar cell has a low electromotive force, and therefore, when combined with a secondary battery, it is preferable to connect the solar cells in series as much as the open voltage of the secondary battery and to use the secondary battery. It is preferable to connect and use circuit elements so that the maximum charging voltage allowed for the battery is not exceeded. Further, when combined with a thin battery, it is preferable that the solar battery is thin so that its shape is not damaged.

[0012]

【Example】

Example 1 Using a stainless steel sheet 4 × 7.5 cm (polymerized part) having a through hole of 0.9 mmφ that had been subjected to a blast treatment of 20 μm as a reaction electrode in a 3 M HBF ₄ aqueous solution containing aniline, at 3 mA / cm ² It was polymerized only on one side. After washing this stainless polyaniline electrode with running water, 0.2N
A sufficient dedoping operation was performed by applying a potential to −0.4 V vs SCE in sulfuric acid. This was reduced with a 20% hydrazine aqueous solution, washed and dried to obtain a polyaniline electrode (thickness 340 μm). Thickness 50 μm, 5.5 ×
SUS sheet with a size of 9 cm, outer diameter 5.5 × 9c
m, thickness 20 having an opening with an inner diameter of 4.1 × 7.6 cm
A modified polypropylene film having a thickness of 0 μm was fixed, and a polyaniline electrode was bonded to the center of the modified polypropylene film using a conductive adhesive. Then, 86.9% of an electrolytic solution prepared by dissolving 3M of LiBF ₄ in a 7/3 (volume ratio) mixed solution of propylene carbonate and dimethoxyethane, ethoxydiethylene glycol acrylate 12.8%, trimethylolpropane triacrylate 0.2%, The solution mixed with benzoin isopropyl ether 0.1% was sufficiently impregnated with polyaniline. The polyaniline portion was compressed to a thickness of 150 μm (about 230 μm including members), and further sufficiently impregnated with the mixed solution to a thickness of 25 μm, 4.5 × 8.
A polypropylene pore filter (0 cm) was laminated on polyaniline so as to be evenly overlapped with the frame portion (sealing portion), and light in high-pressure mercury was irradiated. The electrolytic solution solidified and did not exude even when pressure was applied. The thickness of the power generation element part was 215 μm. This was used as a positive electrode member. Blast-treated stainless steel coated with a coating solution consisting of 47.4 parts by weight of carbon obtained by firing coke at 2500 ° C., 5.2 parts by weight of polyvinylidene fluoride and 47.4 parts by weight of n-methylpyrrolidone. (SUS304) Coated on a current collector (5.5 × 9 cm), dried at 80 ° C., a negative electrode active material layer (4) having a thickness of 20 μm.
X 7.5 cm) was formed. After inserting lithium ions into carbon, the mixed solution was permeated and irradiated with a high pressure mercury lamp to completely solidify the electrolytic solution. The thickness of the power generation element was 100 μm. This was used as a negative electrode member. The positive electrode member and the negative electrode member were laminated, and the three sides were heat-sealed 6.5 mm from the end while uniformly applying (pressing) the power generation element part. Then, the remaining side was sealed under reduced pressure to complete the battery. A charge / discharge test of this non-aqueous electrolyte secondary battery revealed that the initial capacity was 10 mAh. Next, a polycrystalline silicon solar cell showing an electromotive voltage of about 0.7 V per cell was prepared by connecting 6 cells in series. The circuit element shown in FIG. 4 was connected between the secondary battery and the solar cell to produce a combined battery. The battery was stored at room temperature for 2 months in the dark. The secondary battery was completely discharged and showed no capacity. When this secondary battery was subjected to a charge / discharge test again,
The capacity returned to 9.5 mAh.

Comparative Example 1 A battery was prepared in the same manner except that copper was used for the negative electrode current collector layer of the secondary battery of Example 1. The initial capacity of the non-aqueous electrolyte secondary battery was 10 mAh, and it was 2 mAh after storage, which was a great deterioration. When the battery was disassembled, copper was eluted.

Example 2 A stainless steel positive electrode current collector which was blasted with a coating solution consisting of 9.9 parts by weight of polyaniline, 23.1 parts by weight of crystalline V ₂ O _{5 and} 67 parts by weight of n-methylpyrrolidone. The positive electrode active material having a thickness of 60 μm was applied onto the body and dried at 85 ° C. to form a positive electrode active material. In addition, the negative electrode active material layer is 30 μm
And A battery was produced in the same manner as in Example 1 except for this.
The initial capacity of the non-aqueous electrolyte secondary battery was 15 mAh.
The capacity after storage was 14.8 mAh.

Comparative Example 2 A combined battery was prepared in the same manner as in Example 2 except that copper was used for the negative electrode current collector layer. The initial capacity of the non-aqueous electrolyte secondary battery was 15 mAh, and after storage was 3 mAh. When the secondary battery was disassembled, copper was eluted.

Example 3 As a negative electrode active material, 250 parts of natural graphite and coke were used.
A combined battery was produced in the same manner as in Example 2 except that a 1: 1 mixture of carbon fired at 0 ° C. was used and a mixed solvent of propylene carbonate, ethylene carbonate, and dimethyl carbonate was used as the solvent of the electrolytic solution. Initial capacity is 1
The storage capacity was 5.5 mAh, and the storage capacity was 15.2 mAh.

Comparative Example 3 A combined battery was manufactured in the same manner as in Example 3 except that copper was used for the negative electrode current collector layer. The initial capacity of the non-aqueous electrolyte secondary battery was 15.2 mAh, and it was 3 mAh after storage. When the secondary battery was disassembled, copper was eluted.

Comparative Example 4 A combined battery was prepared in the same manner as in Example 3 except that natural graphite was used as the negative electrode active material and the electrolytic solution used in Example 1 was used as the electrolytic solution. Initial capacity is 1.5mA
It was as low as h. As a result of disassembling the secondary battery and examining the battery element, it was found that propylene carbonate reacted with the negative electrode active material.

Example 4 A battery was prepared in the same manner as in Example 3 except that etched aluminum was used as the positive electrode current collector layer. The initial capacity of the non-aqueous electrolyte secondary battery was 15.3 mAh, and the capacity after storage was 15 mAh.

Comparative Example 5 A battery was prepared in the same manner as in Example 4 except that copper was used for the negative electrode current collector layer. The initial capacity of the non-aqueous electrolyte secondary battery is 1
It was 5.1 mAh and after storage was 2.5 mAh.
When the secondary battery was disassembled, it was found that copper was eluted.

Comparative Example 6 A battery was prepared in the same manner as in Example 4 except that 2M LiN (CF ₃ SO ₂ ) ₂ was used as the electrolyte salt. The initial capacity of the non-aqueous electrolyte secondary battery was 14 mAh, but the cycle was only 4 mAh after 20 cycles, and when the cycle was continued after that, holes were formed in the aluminum current collector and dissolution of aluminum occurred. I found out that

Example 5 LiN (CF ₃ SO ₂ ) _{2 having a} concentration of 1.8 M was used as an electrolyte salt.
A combined battery was manufactured in the same manner as in Example 4 except that a mixed electrolyte of 0.2 M concentration of LiBF ₄ was used. The initial capacity of the non-aqueous electrolyte secondary battery was 15.5 mAh, and after storage was 15.2 mAh.

Comparative Example 7 A combined battery was produced in the same manner as in Example 5 except that copper was used for the negative electrode current collector layer. The initial capacity of the secondary battery is 15.2
mAh, and after storage was 2.5 mAh. When the secondary battery was disassembled, copper was eluted.

Specific embodiments of the present invention will be shown below. 1. In a combination battery of at least a positive electrode current collector layer, a positive electrode active material layer, an electrolyte layer, a carbon-based negative electrode active material layer and a laminated structure of a negative electrode current collector layer, a combination battery of a non-aqueous electrolyte secondary battery and a solar cell, wherein: A combined battery of a non-aqueous electrolyte secondary battery and a solar cell, wherein at least the negative electrode current collector layer of the non-aqueous electrolyte secondary battery is made of stainless steel. 2. 2. The combination battery according to 1 above, wherein the non-aqueous electrolyte secondary battery is a lithium non-aqueous electrolyte secondary battery. 3. The combined battery according to 1 or 2 above, wherein the negative electrode active material layer is composed of a composite active material of natural graphite and artificial graphite obtained by firing coke. 4. Artificial graphite is mesophase pitch and /
Alternatively, the combined battery according to the above 3, which is a carbon body obtained by firing coke in a reducing atmosphere at 2500 ° C. or higher. 5. 1, 2, 3 or 4 in which the positive electrode active material layer is a composite active material of an inorganic active material and a conductive polymer active material
Non-combined battery described. 6. 6. The combination battery according to the above 5, which is at least one kind of redox active material selected from the group consisting of conductive polymer materials polyacetylene, polypyrrole, polythiophene, polyaniline and polydiphenylbenzidine. 7. 7. The combined battery according to the above 5 or 6, wherein the inorganic active material is an oxide of a transition metal such as V, Co, Mn, Ni or a composite oxide of the transition metal and an alkali metal. 8. The composite active material of the inorganic active material and the conductive polymer active material is the inorganic active material vanadium pentoxide,
5, wherein the conductive polymer active material is polyaniline
The combined battery according to 6 or 7. 9. 1, 2, 3, wherein the solvent of the electrolyte layer is a mixed solvent of solvents selected from the group consisting of propylene carbonate, ethylene carbonate and dimethyl carbonate,
The combined battery according to 4, 5, 6, 7 or 8. 10. The electrolyte salt of the electrolyte layer has at least the formula LiN
(CF ₃ SO ₂₎ is a mixture of two or more electrolyte salts wherein the 5, 6, 7, 8 or 9 further comprising a lithium (bis) trifluoromethanesulfonate imide represented by ₂ Combination batteries. 11. The electrolyte salt of the electrolyte layer has at least the formula M (BF
₄ ) The above-mentioned 1 which is a mixed electrolyte of at least one tetrafluoroborate salt represented by _X (wherein M is an alkali metal or alkaline earth metal and X is 1 or 2).
The combination battery described in 0. 12. 1, 2, 3, wherein the electrolyte layer is a solid electrolyte,
The combined battery according to 4, 5, 6, 7, 8, 9, 10 or 11. 13. 12. The combined battery according to the above 1, 2, 3, 4, 5, 7, 8, 9, 10 or 11, wherein the positive electrode current collector layer is etched aluminum. 14. 1, 2, 3, 4, 5, 7, 8, 9, 1 in which the carbon negative electrode current collector layer is blasted stainless steel
The combined battery according to 0, 11 or 12.

[0025]

【effect】

1. Claim 1 A combined battery of a lithium non-aqueous electrolyte secondary battery and a solar cell, which is resistant to over-discharge, was provided. 2. [Claim 2] A combination battery having a non-aqueous electrolyte secondary battery having a negative electrode without decomposition of the electrolyte solution while leaving the good potential flatness and current characteristics of natural graphite was obtained. 3. Claims 3 and 4 A combined battery having a non-aqueous electrolyte secondary battery in which the problems of the organic and inorganic electrode active materials are solved is obtained. 4. [Claim 5] A combined battery having a non-aqueous electrolyte secondary battery in which positive and negative electrodes are suppressed from self-discharge and cycle characteristics are improved was obtained. 5. 6. Corrosion of a current collector layer, particularly an aluminum positive electrode current collector layer, is prevented by using an electrolyte solution containing at least two kinds of mixed electrolytes represented by the formula LiN (CF ₃ SO ₂ ) ₂ as an electrolyte. A combined battery having the above non-aqueous electrolyte secondary battery was obtained. 6. 7. A non-aqueous electrolyte secondary in which the surface of the current collector layer is roughened and the adhesion between the electrode active material and the current collector layer is improved without significantly deforming the current collector layer or significantly reducing its strength. A combined battery having a battery was obtained. 7. [Claim 8] By using the solid electrolyte, a combined battery having a non-aqueous electrolyte secondary battery free from liquid leakage and having high safety when the battery is heated can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram conceptually showing a potential change during discharge of a positive electrode when a conventional carbon material-based active material is used for the negative electrode.

FIG. 2 is a diagram conceptually showing a potential change during discharge of the negative electrode when a conventional carbon material-based active material is used for the negative electrode.

FIG. 3 is a diagram conceptually showing a potential change during discharge of the battery when a conventional carbon material-based active material is used for a negative electrode.

FIG. 4 is a circuit diagram of the combined battery of Example 1.

[Explanation of symbols]

 1 Positive electrode potential change 2 Negative electrode potential change 3 Battery voltage A Point where battery voltage becomes 0V

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ms. Kurosawa 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Co., Ltd. (72) Toshiyuki Osawa 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Company Ricoh

Claims (8)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising at least a laminated structure of a positive electrode current collector layer, a positive electrode active material layer, an electrolyte layer, a carbonaceous negative electrode active material layer and a negative electrode current collector layer, and a solar cell. A combined battery comprising a non-aqueous electrolyte secondary battery and a solar cell, wherein at least the negative electrode current collector layer of the non-aqueous electrolyte secondary battery is made of stainless steel. 2. The combined battery of a non-aqueous electrolyte secondary battery and a solar cell according to claim 1, wherein the negative electrode active material layer is composed of a composite active material of natural graphite and artificial graphite obtained by firing coke. . 3. The combined battery of a non-aqueous electrolyte secondary battery and a solar cell according to claim 1, wherein the positive electrode active material layer is a composite active material of an inorganic active material and a conductive polymer active material. . 4. A combination of a non-aqueous electrolyte secondary battery and a solar cell according to claim 3, wherein the inorganic active material is vanadium pentoxide and the conductive polymer active material is polyaniline. battery. 5. The non-aqueous electrolyte secondary battery according to claim 1, wherein the solvent of the electrolyte layer is a mixed solvent of solvents selected from the group consisting of propylene carbonate, ethylene carbonate and dimethyl carbonate. A combination battery with a solar cell. 6. The electrolyte salt of the electrolyte layer has at least the formula L
The non-aqueous electrolyte secondary according to claim 1, which is a mixed electrolyte salt of two or more kinds containing lithium (bis) trifluoromethanesulfonimide represented by iN (CF ₃ SO ₂ ) _2. A combination battery of a battery and a solar cell. 7. The combined battery of a non-aqueous electrolyte secondary battery and a solar battery according to claim 1, 2, 3, 4, 5, or 6, wherein the positive electrode current collector layer is etched aluminum. 8. The electrolyte layer is a solid electrolyte,
A combined battery of the non-aqueous electrolyte secondary battery according to 2, 3, 4, 5, 6 or 7 and a solar cell.