JP2014022321A - Nonaqueous electrolyte secondary battery including scavenger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery excellent in charge/discharge cycle characteristics, in a nonaqueous electrolyte secondary battery including a negative electrode, a positive electrode and a nonaqueous electrolyte interposed between the negative electrode and the positive electrode.SOLUTION: The negative electrode includes a negative electrode active material mainly consisting of a material acting at 0.3 V or more and 2.0 V or less on the basis of the oxidation-reduction potential of lithium metal, and a scavenger comprising a specified organic compound with reducing properties is interposed within a nonaqueous electrolyte secondary battery. Accordingly, impurities inside the battery can be scavenged.

Description

  The present invention relates to an improvement in cycle stability of a nonaqueous electrolyte secondary battery.

Lithium ion secondary batteries are now widely used as power sources for mobile devices. Lithium ion secondary batteries have higher energy density than existing nickel-cadmium secondary batteries and nickel-hydrogen secondary batteries, so they are also expected to be used for large power supplies such as electric vehicles and power storage. .
At present, graphite-based carbon materials are most commonly used as negative electrode materials for lithium ion secondary batteries. Carbon materials have a low voltage of about 0.2 V on a lithium basis, and can increase the voltage of the battery. However, with regard to reliability such as life, batteries with a carbon material as the negative electrode are long in a high temperature environment of, for example, 60 ° C or higher. When used for a long time, the capacity tends to decrease due to the charge / discharge cycle.

Therefore, for example, in Patent Document 1, in order to suppress deterioration of the high-temperature charge / discharge cycle characteristics, a trapping substance that captures impurity ions composed of cations and fluoride ions other than lithium ions generated inside the battery, By holding it on the surface or inside of the positive electrode or the negative electrode, the cation or fluoride ion that causes battery deterioration is prevented from adhering to the negative electrode active material particles. Examples of the trapping substance include activated carbon having a specific surface area of 1000 m ² / g or a pore volume of 0.1 cc / g or more, and an alkaline earth metal oxide.

  In Patent Document 2, cycle characteristics are improved by adding lithium carbonate or / and oxalate to a positive electrode, a negative electrode, or a non-aqueous electrolyte. Patent documents 3 and 4 also disclose an invention in which a specific substance is added to the battery.

JP 2000-77103 A JP 2004-14472 A Japanese Patent Laid-Open No. 11-54149 JP 2011-165343 A

  However, if activated carbon with a large specific surface area is used as described in Patent Document 1, when a kneaded material containing an electrode active material, activated carbon, and a solvent is applied to a current collector, the amount of absorbed solvent of the activated carbon increases. The viscosity of the kneaded product is likely to increase, and the coating workability is reduced. When an alkaline earth metal oxide is supported on the negative electrode, since the oxide is an insulator, the conductive performance of the negative electrode active material may be reduced, and the battery capacity per unit weight of the electrode may be reduced.

  Furthermore, in the structures of Patent Documents 1 to 4, a carbon-based material is selected as the material for the negative electrode active material. However, a non-aqueous electrolyte that uses a material that expresses a higher voltage than the carbon material on the basis of lithium as the negative electrode active material. In the secondary battery, since the substance causing electrode deterioration is different from that of the carbon negative electrode material, it has not been elucidated whether the same effect can be obtained even if a known trapping agent is mixed in the battery.

  The present invention exhibits excellent cycle stability in a non-aqueous electrolyte secondary battery using a negative electrode active material whose main component is a material that operates at 0.3 V or more and 2.0 V or less on the basis of a redox potential of lithium metal. An object of the present invention is to provide a battery that can be used.

In view of the above-mentioned circumstances, the present inventors have conducted extensive studies, and as a result, found that a non-aqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics can be obtained by allowing a capturing agent made of an organic compound to be present in the battery. The present invention has been completed.
The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte interposed between the negative electrode and the positive electrode, wherein the negative electrode is an oxidation-reduction of lithium metal The negative electrode active material which has as a main component the material which operate | moves by 0.3 V or more and 2.0 V or less on an electric potential reference | standard WHEREIN: The trapping agent which consists of an organic compound exists in a battery.

According to this structure, it is possible to obtain a nonaqueous electrolyte secondary battery in which the impurities generated in the battery are captured by the scavenger and the deterioration of the battery characteristics can be reduced even if the charge / discharge cycle is repeated.
It is preferable to select a reducing organic compound as the organic compound contained in the scavenger, and it is preferable to include one or more selected from glucose, cellulose, ethylene glycol, formic acid, oxalic acid, ascorbic acid, and ubiquinone.

Examples of the negative electrode active material that operates at 0.3 V or more and 2 V or less on the basis of the redox potential of lithium metal include lithium titanium oxide and titanium oxide.
Further, as the positive electrode active material constituting the positive electrode, it is preferable to use lithium manganese oxide or a material obtained by substituting a part of manganese of lithium manganese oxide with a different material.
You may make it add in a non-aqueous electrolyte solution as a form which arrange | positions a capture agent in a non-aqueous electrolyte secondary battery. Moreover, you may make it exist in the inside and / or surface of a positive electrode, a negative electrode, and a separator. In either case, impurities generated in the battery can be efficiently captured by the scavenger, and charge / discharge cycle characteristics can be improved.

  The non-aqueous electrolyte may be in a gel form.

  The non-aqueous electrolyte secondary battery of the present invention has an excellent effect of having excellent cycle stability as compared with a non-aqueous electrolyte secondary battery not containing a scavenger by containing a scavenger inside the battery.

Embodiments of the present invention will be described below.
The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
<Capturing agent>
The structure for providing the scavenger of the present invention inside the nonaqueous electrolyte secondary battery is not limited. For example, the scavenger may be added to the nonaqueous electrolyte as it is. When added to the non-aqueous electrolyte, the concentration is preferably 0.01 weight percent (wt%) or more and 3 wt% or less. Above this range, it may be difficult to dissolve the scavenger. If it is below this range, the function of trapping impurities will be reduced, which is not preferable.

It is preferable to select a reducing organic compound as the organic compound contained in the scavenger, and one or more selected from glucose, cellulose, ethylene glycol, formic acid, oxalic acid, ascorbic acid, and ubiquinone are preferable.
Further, the scavenger may be present on the surface and / or inside of the positive electrode and the negative electrode. When the electrode active material, the conductive additive and the binder are mixed to form an electrode active material mixture (slurry), the addition of the trapping agent makes it possible to efficiently disperse the trapping agent. To preferred. The scavenger may be present on the electrode surface. For this purpose, it is preferable from the viewpoint of dispersion that the electrode is immersed in a solution in which the capture agent is dissolved and dried after the electrode is manufactured. Alternatively, a polymer film containing a scavenger may be prepared and adhered to the electrode surface.

  A scavenger may be present on the surface and / or inside of the separator. When a porous membrane is used as the separator, it can be made to exist inside the separator if a capture agent is added to the monomer solution when the separator is made of a polymer membrane. Moreover, you may make the separator produced with the normal manufacturing method exist on the surface by immersing in the solution which melt | dissolved the trapping agent, and making it dry.

When using a nonwoven fabric as a separator, it is preferable to add a scavenger to the monomer solution when producing the fiber. Similarly to the porous membrane separator, a nonwoven fabric separator produced by a normal production method can be present on the surface and inside by being immersed in a solution in which the capture agent is dissolved and dried.
In order to maintain the effect of the scavenger in the separator for a long period of time, it is preferable to encapsulate the scavenger in a polymer and gradually release it. A separator may be produced using this polymer film or fiber, or the effect of the scavenger can be maintained for a long time even if this polymer film or fiber is simply present in the battery.

  In addition, as a modified example of the structure of the nonaqueous electrolyte secondary battery according to the embodiment of the present invention, an independent separator is not necessarily used unless the positive electrode and the negative electrode are in direct contact. That is, a structure without a separator is also conceivable. In this case, a gel-like material may be used as the nonaqueous electrolyte in order to prevent contact between the positive electrode and the negative electrode. In the case of using a gel-like material, the nonaqueous electrolyte may be impregnated in the positive electrode and the negative electrode, or may be in a state only between the positive electrode and the negative electrode. When the gel-like nonaqueous electrolyte is used in this way, the scavenger may be dispersed and arranged inside the gel-like nonaqueous electrolyte.

<Negative electrode>
The negative electrode used in the nonaqueous electrolyte secondary battery of the present invention is composed of at least a negative electrode active material or a negative electrode active material and a current collector, and may contain a conductive additive and a binder as necessary.
As the negative electrode active material, it is preferable to use a material that operates at 0.3 V or more and 2.0 V or less on the basis of a redox potential of lithium metal. For example, as a material of the negative electrode active material, transition metal-containing oxides such as molybdenum oxide, niobium oxide, manganese oxide, lithium manganese oxide, titanium oxide, and lithium titanium oxide, transitions such as nickel nitride, manganese nitride, and iron nitride Transition metal sulfides such as metal nitride, nickel sulfide and manganese sulfide, phosphides such as nickel phosphide, manganese phosphide and iron phosphide and phosphorus alone, fluorides such as iron fluoride and nickel fluoride, alkali metals or / And at least one selected from the group consisting of metals that form alloys with alkaline earth metals.

When a negative electrode active material is configured with a carbon-based material as in the past, there is a problem that the negative electrode deteriorates due to volume change accompanying lithium insertion / extraction when the charge / discharge cycle is repeated, and the capacity of the battery decreases. As the negative electrode material, it is particularly preferable to use titanium oxide or lithium titanium oxide, which is a robust material that hardly changes in volume due to insertion / extraction of lithium.
The lithium titanium oxide is preferably expressed as Li ₄ Ti ₅ O ₁₂ as a molecular formula. Among these, the use of a spinel structure is particularly preferable because the expansion and contraction of the active material in the lithium ion insertion / desorption reaction is small. The lithium titanium oxide may contain a trace amount of elements other than lithium and titanium, such as Nb.

  The lithium titanium oxide can be obtained by heat-treating a lithium compound or a titanium compound at 500 ° C. or higher and 1500 ° C. or lower. When the temperature is lower than 500 ° C. or higher than 1500 ° C., there is a tendency that it is difficult to obtain a lithium titanium oxide having a desired structure. In order to improve the crystallinity of the lithium titanium oxide, after the heat treatment, the heat treatment may be performed again at 500 ° C. or more and 1500 ° C. or less. The temperature of the reheating treatment may be the same as or different from the temperature at which the heat treatment is first performed. The heat treatment may be performed in the presence of air or in the presence of an inert gas such as nitrogen or argon. Although the structure of a heat treatment furnace is not specifically limited, For example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln etc. can be used.

As the lithium compound, for example, lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium oxalate, lithium halide and the like can be used. These lithium compounds may be used alone or in combination of two or more.
As the titanium compound, for example, titanium oxide such as titanium dioxide and titanium monoxide can be used.

The compounding ratio of the lithium compound and the titanium compound may be somewhat widened at the atomic ratio of lithium and titanium, around Ti / Li = 1.25, depending on the properties of the raw materials and heating conditions.
The particle diameter of the lithium titanium oxide is preferably 0.5 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less from the viewpoint of handling. The particle diameter is a value obtained by measuring the size of each particle from SEM and TEM images and calculating the average particle diameter.

The specific surface area of the lithium titanium oxide is preferably 0.1 m ² / g or more and 50 m ² / g or less because a desired output density is easily obtained. The specific surface area can be calculated by measurement using a mercury porosimeter and the BET method.
The bulk density of the lithium titanium oxide is preferably 0.2 g / cm ³ or more and 1.5 g / cm ³ or less. 0.2 g / cm in the case of less than ³ tend to be economically disadvantageous because it requires a large amount of solvent in the step of preparing the slurry described below, 1.5 g / cm ³ greater than the later of conductive agent, and a binder Tend to be difficult to mix.

The titanium oxide is preferably represented by TiO2 as a molecular formula. As the crystal structure, anatase type, ramsdelite type, bronze type, and hollandite type are preferable, and anatase type or bronze type (TiO ₂ (B)) is particularly preferable from the viewpoint of potential flatness and the number of potential flat portions. The titanium oxide may contain a trace amount of elements other than titanium, such as Nb, like the lithium titanium oxide.

Anatase type TiO ₂ can be obtained by a method of treating titanium chloride at a high temperature, a method of hydrolyzing titanium sulfate and then firing it. TiO2 (B) can be obtained by hydrothermal synthesis at 170 ° C. The TiO ₂ in sodium hydroxide solution. In addition, after synthesis of A ₂ Ti ₄ O ₉ or BTi ₄ O ₉ (A: alkali metal, B: alkaline earth metal) by solid phase synthesis using TiO ₂ and an alkali metal or alkaline earth metal compound, hydrochloric acid It can also be obtained by ion exchange in an aqueous solution and heat dehydration at 400 to 900 ° C. Hydrothermal synthesis, the solid phase synthesis both raw TiO2 is preferably anatase TiO _2. The heat treatment may be performed in the presence of air or in the presence of an inert gas such as nitrogen or argon. The structure of the heat treatment furnace is not particularly limited, and for example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln, or the like can be used.

As the alkali metal compound and the alkaline earth metal compound, a hydrochloride, carbonate, nitrate, sulfate, acetate, oxalate, or the like can be used. These compounds may be used alone or in combination of two or more.
The particle diameter and specific surface area of the titanium oxide are preferably in the same numerical range as the lithium titanium oxide.

A binder (binder) may be used for the negative electrode. The binder is not particularly limited. For example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), styrene-butadiene rubber, polyimide, and their At least one selected from the group consisting of derivatives can be used.
The binder is preferably dissolved or dispersed in a non-aqueous solvent or water from the viewpoint of easy production of the negative electrode. The non-aqueous solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, and tetrahydrofuran. You may add a dispersing agent and a thickener to these.

In the present invention, the amount of the binder contained in the negative electrode is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 1 part by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the negative electrode active material. If it is the said range, the adhesiveness of a negative electrode active material and a conductive support material will be maintained, and adhesiveness with a collector can fully be acquired.
The negative electrode of the present invention may contain a conductive additive as necessary. Although it does not specifically limit as a conductive support material, A carbon material or / and a metal microparticle are preferable. Examples of the carbon material include natural graphite, artificial graphite, vapor-grown carbon fiber, carbon nanotube, acetylene black, ketjen black, and furnace black. Examples of the metal fine particles include copper, aluminum, nickel, and an alloy containing at least one of these. Further, the fine particles of inorganic material may be plated. These carbon materials and metal fine particles may be used alone or in combination of two or more.

In the present invention, the amount of the conductive additive contained in the negative electrode is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 1 part by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the negative electrode active material. If it is the said range, the electroconductivity of a negative electrode will be ensured.
Examples of the current collector used for the negative electrode of the non-aqueous electrolyte secondary battery of the present invention include copper, aluminum, nickel, an alloy containing at least one of these, and a conductive polymer. Examples of the shape include a foil shape, a mesh shape, a punching shape, an expanded shape, and a foam structure.

  Here, the mesh shape is a woven or unworked cloth made of metal or conductive polymer fibers. The thickness of the fiber is preferably 50 μm or more and 2000 μm or less. When the thickness is less than 50 μm, the strength of the current collector is weak. Therefore, when the active material mixture is supported on the current collector, the current collector tends to be easily broken. On the other hand, when a fiber thicker than 2000 μm is used, the opening becomes too large to make the porosity described later, and it tends to be difficult to hold the active material mixture by the mesh.

The punching shape is a plate in which holes such as a circle, a rectangle, or a hexagon are formed, and a metal plate is punched metal. The porosity corresponds to the hole area ratio, which is determined by the hole diameter and bone ratio, hole shape, and hole arrangement. The shape of the hole is not particularly limited, but from the viewpoint of increasing the open area ratio, a round hole 60 ° staggered type and a square hole staggered / parallel type are preferable.
The expanded shape is a staggered cut made on a plate and stretched to form a mesh. Expanded metal is made of metal. The porosity corresponds to the hole area ratio, which is determined by the hole diameter and bone ratio, hole shape, and hole arrangement.

The foam structure has a three-dimensional network structure like a sponge and has continuous pores. The structure is determined by the pore size and porosity. The shape and diameter of the continuous holes are not particularly limited, but a structure having a high specific surface area is preferable.
The metal used in the current collector of the present invention is only required to be stable between negative electrode operating voltages. When the negative electrode operating potential is 0.6 V or less on the basis of lithium, copper and its alloys are preferable, and when 0.6 V or more, aluminum and The alloy is preferred.

  The negative electrode of the present invention is produced by, for example, supporting a negative electrode mixture comprising a negative electrode active material, a conductive aid, and a binder on a current collector. It is preferable to prepare a negative electrode by preparing a slurry with a binder and a solvent, filling and applying the obtained slurry to the pores of the current collector and the outer surface thereof, and then removing the solvent. Further, the mixture of the negative electrode active material, the conductive additive and the binder may be supported on the current collector as it is without being dispersed in the solvent.

  The slurry is not particularly limited, but it is preferable to use a ball mill, a planetary mixer, a jet mill, or a thin film swirling mixer because the negative electrode active material, the conductive additive, the binder, and the solvent can be mixed uniformly. Although the preparation of the slurry is not particularly limited, it may be prepared by mixing the negative electrode active material, the conductive additive, and the binder and then adding a solvent, or the negative electrode active material, the conductive additive, the binder, and the solvent together. You may mix and produce.

Further, as described above, when the scavenger is present inside the negative electrode active material, the scavenger is added when the negative electrode active material, the conductive additive and the binder are mixed.
The solid content concentration of the slurry is preferably 30 wt% or more and 80 wt% or less. If it is less than 30 wt%, the viscosity of the slurry tends to be too low, whereas if it is higher than 80 wt%, the viscosity of the slurry tends to be too high, and it may be difficult to form an electrode described later.

  The solvent used for the slurry is preferably a non-aqueous solvent or water. The non-aqueous solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, and tetrahydrofuran. Moreover, you may add a dispersing agent and a thickener to these.

  The method of supporting the negative electrode mixture on the current collector is not particularly limited. For example, the method of removing the solvent after applying the slurry with a doctor blade, die coater, comma coater, etc., or the solvent after adhering to the current collector by spraying. A method of removing the solvent and a method of removing the solvent after impregnating the current collector in the slurry are preferable. The method for removing the solvent is preferable because it is easy to dry using an oven or a vacuum oven. Examples of the atmosphere include room temperature or high temperature air, an inert gas, and a vacuum state. The negative electrode may be formed before or after forming the positive electrode described later. If the negative electrode active material, conductive additive and binder mixture are not dispersed in the solvent, the negative electrode active material, conductive additive and binder can be mixed uniformly, so use a ball mill, planetary mixer, jet mill, or thin film swirl mixer. After preparing the mixture, it is preferable to carry the mixture on the current collector. The method of supporting the mixture on the current collector is not particularly limited, and a method of pressing the mixture after it is packed in the current collector is preferable. The press may be heated. Moreover, you may compress a negative electrode using a roll press machine etc. after negative electrode preparation. The electrode may be compressed before or after the positive electrode is formed.

<Positive electrode>
The positive electrode used in the nonaqueous electrolyte secondary battery of the present invention is composed of at least a positive electrode mixture and a current collector. A positive electrode mixture contains a positive electrode active material and a binder at least, and a conductive support material as needed.
The positive electrode active material is not particularly limited, but a composite oxide, composite nitride, composite fluoride, composite containing an alkali metal and / or alkaline earth metal having an operating potential of 2.8 V to 5.2 V on the basis of lithium. At least one selected from the group consisting of sulfides, composite selenides and the like can be used.

  The positive electrode active material is particularly preferably a lithium transition metal compound, and examples include a lithium cobalt compound, a lithium nickel compound, a lithium manganese compound, and a lithium iron compound. Further, the transition metal is not limited to one type, and may be two or more types, and examples thereof include a lithium cobalt nickel manganese compound and a lithium nickel manganese compound. Moreover, since the effect which improves the stability of a lithium transition metal compound is high, elements, such as aluminum, magnesium, titanium, chromium, iron, may be contained in trace amounts, for example.

A binder may be used for the positive electrode, and those exemplified for the binder used for the negative electrode described above can be similarly applied. The binder is preferably dissolved or dispersed in a non-aqueous solvent or water from the viewpoint of easy production of the positive electrode. As the non-aqueous solvent, those exemplified above for the non-aqueous solvent can be similarly applied. You may add a dispersing agent and a thickener to these.
If necessary, the positive electrode of the present invention may contain a conductive additive, and the conductive additive is not particularly limited, but is preferably a carbon material or fine metal particles. Examples of the carbon material include the same carbon materials that can be contained in the above-described negative electrode. Examples of the metal fine particles include aluminum and aluminum alloys. Further, the fine particles of inorganic material may be plated. These carbon materials and metal fine particles may be used alone or in combination of two or more.

  In the present invention, the amount of the conductive additive contained in the positive electrode is preferably 1 to 30 parts by weight, more preferably 1 to 15 parts by weight, with respect to 100 parts by weight of the positive electrode active material. If it is the said range, the electroconductivity of a positive electrode will be ensured. Moreover, adhesiveness with a binder is maintained and sufficient adhesiveness with a collector can be obtained. On the other hand, when a larger amount of conductive aid than 30 parts by weight is used, the volume occupied by the conductive aid increases and the energy density tends to decrease.

As the current collector used for the positive electrode of the nonaqueous electrolyte secondary battery of the present invention, those exemplified for the current collector used for the negative electrode described above can be similarly applied. The material of the current collector is preferably aluminum or an alloy thereof from the viewpoint of weight.
The positive electrode of the present invention is produced by supporting a positive electrode active material, a conductive additive, and a positive electrode active material layer of a binder on a current collector. From the ease of the production method, the positive electrode active material, the conductive additive, A method is preferred in which a slurry is prepared with a binder and a solvent, and the positive electrode is prepared by removing the solvent after filling and applying the obtained slurry to the pores and the outer surface of the current collector. Alternatively, the mixture of the positive electrode active material, the conductive additive and the binder may be supported on the current collector without being dispersed in the solvent. As described above, when the scavenger is present inside the positive electrode active material, the scavenger is added when the positive electrode active material, the conductive additive and the binder are mixed.

The slurry preparation method, the solid content concentration of the slurry, the solvent used in the slurry, the method of supporting the active material layer on the current collector, and the electrode compression described in the preparation of the negative electrode described above are similarly applied to the preparation of the positive electrode. it can.
<Capacity ratio and area ratio of negative electrode to positive electrode>
The ratio of the electric capacity of the positive electrode and the electric capacity of the negative electrode in the nonaqueous electrolyte secondary battery of the present invention preferably satisfies the following formula (1).

0.7 ≦ B / A ≦ 1.3 (1)
In the above formula (1), A represents the electric capacity per 1 cm ² of the positive electrode, and B represents the electric capacity per 1 cm ² of the negative electrode.
When B / A is less than 0.7, the potential of the negative electrode may become the deposition potential of alkali metal and / or alkaline earth metal during overcharge, while B / A is greater than 1.3. Side reactions may occur because there are many negative electrode active materials not involved in the battery reaction.

The area ratio between the positive electrode and the negative electrode in the nonaqueous electrolyte secondary battery of the present invention preferably satisfies the following formula (2).
1 ≦ D / C ≦ 1.2 (2)
(However, C represents the area of the positive electrode, and D represents the area of the negative electrode.)
When D / C is less than 1, for example, when B / A = 1 as described above, the capacity of the negative electrode is smaller than that of the positive electrode. Therefore, the potential of the negative electrode during alkaline overcharge is alkali metal and / or alkaline earth metal. There is a risk of deposition potential. On the other hand, if D / C is greater than 1.2, the negative electrode active material not involved in the battery reaction may cause a side reaction because the portion of the negative electrode that is not in contact with the positive electrode is large. Although control of the area of a positive electrode and a negative electrode is not specifically limited, For example, in the case of slurry coating, it can carry out by controlling the coating width.

<Separator>
Examples of the separator used in the nonaqueous electrolyte secondary battery of the present invention include porous materials and nonwoven fabrics. As the material of the separator, those that do not dissolve in the organic solvent constituting the nonaqueous electrolyte are preferable. Specifically, polyolefin polymers such as polyethylene and polypropylene, polyester polymers such as polyethylene terephthalate, cellulose, glass Such inorganic materials are mentioned.

The thickness of the separator is preferably 1 to 500 μm. If it is less than 1 μm, it tends to break due to insufficient mechanical strength of the separator and cause an internal short circuit. On the other hand, when it is thicker than 500 μm, the load characteristics of the battery tend to be reduced due to the increase in the internal resistance of the battery and the distance between the positive and negative electrodes. A more preferable thickness is 10 to 50 μm.
The area ratio between the separator and the negative electrode used in the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, but preferably satisfies the following formula (3).

1 ≦ F / E ≦ 1.5 (3)
(However, E represents the area of the negative electrode, and F represents the area of the separator.)
When F / E is less than 1, the positive electrode and the negative electrode are in contact with each other, and when F / E is greater than 1.5, the volume required for the exterior increases, and the output density of the battery may decrease.
Also, as described above, the scavenger can be present on the surface and / or inside of the separator.

<Nonaqueous electrolyte>
The non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but a non-aqueous electrolyte obtained by dissolving a solute in a non-aqueous solvent, and a non-aqueous electrolyte obtained by dissolving a solute in a non-aqueous solvent as a polymer. An impregnated gel non-aqueous electrolyte or the like can be used.
The non-aqueous solvent preferably includes a cyclic aprotic solvent and / or a chain aprotic solvent. Examples of the cyclic aprotic solvent include cyclic carbonates, cyclic esters, cyclic sulfones and cyclic ethers. Examples of the chain aprotic solvent include chain carbonates, chain carboxylic acid esters and chain ethers. In addition to the above, a solvent generally used as a solvent for nonaqueous electrolytes such as acetonitrile may be used. More specifically, dimethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate, tetrahydrofuran, γ-butyrolactone, 1,2-dimethoxyethane, Sulfolane, dioxolane, methyl propionate and the like can be used. These solvents may be used alone or as a mixture of two or more. However, in view of the ease of dissolving the solute described below and the high conductivity of lithium ions, a mixture of two or more of these solvents. Is preferably used. A gel-like non-aqueous electrolyte in which a non-aqueous electrolyte is impregnated in a polymer can also be used.

The solute is not particularly limited. For example, lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiBOB (Lithium Bis (Oxalato) Borate), LiN (SO ₂ CF ₃ ) ₂ , Sodium salts such as NaClO ₄ , NaBF ₄ , NaPF _{6 and the} like are preferable because they are easily dissolved in a solvent. The concentration of the solute contained in the nonaqueous electrolyte is preferably 0.5 mol / L or more and 2.0 mol / L or less. If it is less than 0.5 mol / L, the desired ionic conductivity may not be exhibited. On the other hand, if it is higher than 2.0 mol / L, the solute may not be dissolved any more, and the viscosity increases and the load characteristic decreases. To do. The non-aqueous electrolyte may contain a trace amount of a flame retardant, a stabilizer and the like.

As described above, it is preferable to add the scavenger of the present invention to the nonaqueous electrolyte.
The amount of the nonaqueous electrolyte used in the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, but is preferably 0.1 mL or more per 1 Ah of battery capacity. If it is less than 0.1 mL, the conduction of lithium ions accompanying the electrode reaction may not catch up, and the desired battery performance may not be exhibited. The nonaqueous electrolyte may be added to the positive electrode, the negative electrode and the separator in advance, or may be added after winding or laminating a separator disposed between the positive electrode side and the negative electrode side.
As described above, the non-aqueous electrolyte is not limited to the non-aqueous electrolyte solution as long as contact between the positive electrode and the negative electrode can be prevented. A gel-like non-aqueous electrolyte may be used. When using a gel-like non-aqueous electrolyte, it may be gelled after impregnation with a monomer, or may be placed between the positive electrode and the negative electrode after gelling in advance. A positive electrode and a negative electrode may be impregnated with a nonaqueous electrolyte, and a positive electrode. The state which exists only between negative electrodes may be sufficient.

<Structure of non-aqueous electrolyte secondary battery>
The positive electrode and the negative electrode of the non-aqueous electrolyte secondary battery of the present invention may have a form in which the same electrode is formed on both surfaces of the current collector, and the positive electrode is formed on one surface of the current collector and the negative electrode is formed on one surface. In other words, in the case of a bipolar type, a conductive material and / or an insulating material is interposed between the positive electrode and the negative electrode in order to prevent a liquid junction between the positive electrode and the negative electrode through the current collector. Has been placed. In the case of a bipolar electrode, a separator is disposed between the positive electrode side and the negative electrode side of the adjacent bipolar electrode, and in the layer where each positive electrode side and the negative electrode side face each other, there is a liquid junction to other parts. In order to prevent this, an insulating material is disposed around the positive and negative electrodes.

  The non-aqueous electrolyte secondary battery of the present invention may be wound or laminated with a laminate film after the laminate is wound, or may be rectangular, elliptical, cylindrical, coin-shaped, button-shaped, or sheet-shaped. It may be packaged with a metal can. The exterior may be provided with a mechanism for releasing the generated gas or the like. Moreover, a mechanism for injecting a capturing agent for recovering the function of the deteriorated nonaqueous electrolyte secondary battery from the outside of the battery may be provided. The number of stacked layers can be stacked until a desired battery capacity is exhibited.

  The nonaqueous electrolyte secondary battery of the present invention can be formed into an assembled battery by connecting a plurality of the nonaqueous electrolyte secondary batteries. The assembled battery of the present invention can be produced by appropriately connecting in series or in parallel according to a desired size, capacity, and voltage. Moreover, it is preferable that a control circuit is attached to the assembled battery in order to confirm the state of charge of each battery and improve safety.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.
(Manufacture of negative electrode)
Li ₄ Ti ₅ O ₁₂ as a negative electrode active material is described in the literature (“Zero-Strain Insertion Material of Li [Li1 / 3Ti5 / 3] O4 for Rechargeable Lithium Cells” J. Electrochem. Soc., Volume 142, Issue 5, pp. 1431-1435 (1995)).

That is, first, titanium dioxide and lithium hydroxide are mixed so that the molar ratio of titanium and lithium is 5: 4, and then this mixture is heated at 800 ° C. for 12 hours in a nitrogen atmosphere to obtain a negative electrode active material. Produced.
100 parts by weight of the negative electrode active material, 3.2 parts by weight of a conductive additive (acetylene black), and PVdF binder (KF7305, manufactured by Kureha Chemical Co., Ltd.) (solid content concentration 5 wt%, NMP solution) are solid content 3.2. A slurry was prepared by mixing parts by weight. The slurry was applied to aluminum expanded metal (LW × SW = 8 × 4), and then vacuum dried at 150 ° C. to prepare a negative electrode.

(Manufacture of positive electrode)
The positive electrode active material Li _1.1 Al _0.1 Mn _1.8 O ₄ is described in the literature ("Lithium Aluminum Manganese Oxide Having Spinel-Framework Structure for Long-Life Lithium-Ion Batteries" Electrochemical and Solid-State Letters Volume 9, Issue 12 , Pages A557 (2006)).

  That is, an aqueous dispersion of manganese dioxide, lithium carbonate, aluminum hydroxide, and boric acid was prepared, and a mixed powder was prepared by a spray drying method. At this time, the amounts of manganese dioxide, lithium carbonate and aluminum hydroxide were adjusted so that the molar ratio of lithium, aluminum and manganese was 1.1: 0.1: 1.8. Next, the mixed powder was heated at 900 ° C. for 12 hours in an air atmosphere, and then again heated at 650 ° C. for 24 hours. Finally, the powder was washed with water at 95 ° C. and dried to prepare a positive electrode active material.

  100 parts by weight of this positive electrode active material, 3.2 parts by weight of a conductive additive (acetylene black), and PVdF binder (KF7305, manufactured by Kureha Chemical Co., Ltd.) (solid content concentration 5 wt%, NMP solution) are obtained with a solid content of 3.2. A slurry was prepared by mixing parts by weight. The slurry was applied to aluminum expanded metal (LW × SW = 8 × 4), and then vacuum dried at 150 ° C. to produce a positive electrode.

(Measurement of negative and positive electrode capacities)
Each capacity | capacitance of the produced positive electrode and negative electrode was measured as follows.
The produced negative electrode and positive electrode were each punched out to 16 mmΦ and used as working electrodes. As a counter electrode, a lithium metal plate was punched in the same area as the working electrode. These were stacked in a laminate cell in the order of working electrode / separator (Celgard # 2500, manufactured by Celgard) / counter electrode, and 1 mol / L of LiPF ₆ was dissolved in a nonaqueous solvent of ethylene carbonate / dimethyl carbonate = 3/7 vol%. 0.5 mL of the solution was put into a positive half-cell and a negative half-cell, respectively. The half-cell was allowed to stand at 25 ° C. for one day, and then connected to a charge / discharge test apparatus (HJ1005SD8, manufactured by Hokuto Denko). For these half-cells, constant current discharge was repeated 5 times at 25 ° C. and 1 mA, and the fifth result was defined as the capacity of the negative electrode or the positive electrode.

(Manufacture of non-aqueous electrolyte secondary batteries)
Nonaqueous electrolyte secondary batteries (Examples and Comparative Examples) were produced as follows.
<Example 1>
The produced positive electrode, negative electrode and separator were laminated in the order of positive electrode / separator / negative electrode. Two sheets of polypropylene nonwoven fabric (25 μm, 55 cm ² ) were used for the separator. Aluminum tabs were vibration welded to the positive and negative electrodes at both ends, and then placed in a bag-like aluminum laminate sheet. 4 mL of nonaqueous electrolyte (ethylene carbonate / dimethyl carbonate = 3/7 vol%, LiPF ₆ 1 mol / L) added with 0.5 wt% of glucose as a scavenger was added, and then sealed with reduced pressure to seal it with non-aqueous electrolyte. An electrolyte secondary battery (Li ₄ Ti ₅ O ₁₂ / Li _1.1 Al _0.1 Mn _1.8 O ₄ battery) was produced.
<Examples 2 to 4>
Non-aqueous secondary batteries (Li ₄ Ti ₅ O ₁₂ / Li ₁₎ were used in the same manner as in Example 1 except that ethylene glycol, ascorbic acid, and ubiquinone 1 wt% were used instead of glucose as the scavenger. _.1 Al _0.1 Mn _1.8 O ₄ battery).
<Examples 5 and 6>
In Example 1, glucose concentrations of 1 wt% and 3 wt% were designated as Examples 5 and 6, respectively, and the non-aqueous secondary battery (Li ₄ Ti ₅ O ₁₂ / Li _1.1 Al ₀ was obtained in the same manner as in Example 1. _.1 Mn _1.8 O ₄ battery).

<Comparative Examples 1-3>
In Example 1, a non-aqueous secondary battery (Li ₄ Ti ₅ O) was added in the same manner as in Example 1 except that no scavenger was added or the glucose concentration was 0.005 wt% and 5 wt%, respectively. ₁₂ / Li _1.1 Al _0.1 Mn _1.8 O ₄ battery).
<Example 7>
A non-aqueous secondary battery (Li ₄ Ti ₅ O ₁₂ / Li _1.1 Al _0.1 Mn _1.8 O ₄ battery) was used in the same manner as in Example 1 except that a cellulose nonwoven fabric was present between the separators as a scavenger. Produced.

<Example 8>
A non-aqueous secondary battery (Li ₄ Ti ₅ O ₁₂ / LiNi _0.5 Mn _1.5 O ₄ battery) as in Example 1 except that the positive electrode material was LiNi _0.5 Mn _1.5 O ₄ (LiNiMO). ) Was produced. LiNi _0.5 Mn _1.5 O ₄ is published in literature ("Topotactic Two-Phase Reactions of Li [Ni1 / 2Mn3 / 2] O4 (P4332) in Nonaqueous Lithium Cells" J. Electrochem. Soc., Volume 151, Issue 2, pp. A296-A303 (2004)).
<Comparative Example 4>
A nonaqueous secondary battery (Li ₄ Ti ₅ O ₁₂ / LiNi _0.5 Mn _1.5 O ₄ battery) was produced in the same manner as in Example 8 except that the scavenger was not added in Example 8.
<Example 9>
A non-aqueous secondary battery (TiO ₂ (B) / Li _1.1 Al _0.1 Mn ₁ ) as in Example 1 except that titanium oxide TiO ₂ (B) was used as the negative electrode active material in Example _{1. .8} O ₄ battery). The negative electrode material TiO ₂ (B) was prepared by the method described in the literature (Material Research Bulletin Vol. 15, pp. 1129-1133 (1980)).
<Comparative Example 5>
A non-aqueous secondary battery (TiO ₂ (B) / Li _1.1 Al _0.1 Mn _1.8 O ₄ battery) was produced in the same manner as in Example 9 except that the scavenger was not added in Example 9. .
<Example 10>
A nonaqueous electrolyte battery (as in Example 1), except that NaNi _0.5 Mn _0.5 O ₂ and a sodium ion-containing nonaqueous electrolyte (PC, NaPF ₆ , 1.0 mol / L) were used as the positive electrode active material. Li ₄ Ti ₅ O ₁₂ / NaNi _0.5 Mn _0.5 O ₂ battery) was produced. The positive electrode material NaNi _0.5 Mn _0.5 O ₂ was prepared by the method described in the literature (S. Komaba et al., Ecs Transactions, 16, pp. 43-55 (2009)).

<Comparative Example 6>
A nonaqueous electrolyte battery (Li ₄ Ti ₅ O ₁₂ / NaNi _0.5 Mn _0.5 O ₂ battery) was produced in the same manner as in Example 10 except that the scavenger was not added.

(Measurement of cycle characteristics)
About Examples 1-10 and Comparative Examples 1-6, after charging / discharging was repeated using the charging / discharging test apparatus (HJ1005SD8; Hokuto Denko Co., Ltd.), the battery capacity maintenance rate was measured. The measurement conditions were a temperature of 45 ° C. and a current value of 1 hour rate.
The voltage ranges of Examples 1 to 7 and 9 and Comparative Examples 1 to 3 and 5 were set to 1 to 3 V, and the voltage ranges of Examples 8 and 10 and Comparative Examples 4 and 6 were set to 1 V to 3.2 V.
The number of cycles in Examples 1 to 9 and Comparative Examples 1 to 5 was 500, and the number of cycles in Example 10 and Comparative Example 6 was 100. The measured battery capacity retention rate is shown in Table 1.

  As is clear from Table 1, the nonaqueous electrolyte secondary battery of Comparative Examples 1 and 2 in which no scavenger is added or the concentration of the scavenger is very low is 85%, whereas the scavenger is 85%. The nonaqueous electrolyte secondary batteries of Examples 1 to 7 of the present invention to which are added respectively are 87 to 92%, and the nonaqueous electrolyte secondary batteries of Examples 1 to 7 of the present invention are the comparative examples 1 and 2. It can be seen that the cycle stability is improved as compared with the nonaqueous electrolyte secondary battery. In addition, as in Comparative Example 3, when the scavenger (glucose) was added excessively, the battery capacity retention rate increased, but the dispersion was poor.

Further, the nonaqueous electrolyte secondary battery of Comparative Example 4 in which no scavenger is added has a battery capacity retention rate of 80%, whereas the nonaqueous electrolyte of Example 8 of the present invention in which a scavenger (glucose) is added. The secondary battery is 83%, which indicates that the cycle stability is improved as compared with the nonaqueous electrolyte secondary battery of Comparative Example 4.
Further, the non-aqueous electrolyte secondary battery of Comparative Example 5 to which no scavenger is added has a battery capacity retention rate of 70%, whereas the non-aqueous electrolyte of Example 9 of the present invention in which a scavenger (glucose) is added. The secondary battery is 77%, and it can be seen that the cycle stability is improved as compared with the nonaqueous electrolyte secondary battery of Comparative Example 5.

Further, the nonaqueous electrolyte secondary battery of Comparative Example 6 to which no scavenger was added had a battery capacity retention rate of 61%, whereas the nonaqueous electrolyte of Example 10 of the present invention in which a scavenger (glucose) was added was used. The secondary battery is 65%, which indicates that the cycle stability is improved as compared with the nonaqueous electrolyte secondary battery of Comparative Example 6.
From the above results, it can be seen that the cycle stability is improved by the presence of a reducing substance as a scavenger in the battery.

Claims (9)

  A nonaqueous electrolyte secondary battery comprising a negative electrode, a positive electrode, and a nonaqueous electrolyte interposed between the negative electrode and the positive electrode, wherein the negative electrode is 0.3 V or more and 2.0 V or less based on a redox potential of lithium metal A non-aqueous electrolyte secondary battery including a negative electrode active material whose main component is a material that operates in a battery and having a scavenger made of an organic compound interposed inside the battery. The nonaqueous electrolyte secondary battery according to claim 1, wherein the scavenger contains one or more selected from glucose, cellulose, ethylene glycol, formic acid, oxalic acid, ascorbic acid, and ubiquinone. The nonaqueous electrolyte secondary battery according to claim 1, wherein lithium titanium oxide or titanium oxide is used as a negative electrode active material constituting the negative electrode.   The positive electrode active material which comprises the said positive electrode used the lithium manganese oxide or the material which substituted a part of lithium manganese oxide by the different metal or the different material. Non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the organic substance is added to the nonaqueous electrolyte. A porous film serving as a separator is interposed between the negative electrode and the positive electrode,
The nonaqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the organic substance is present on or inside the porous membrane of the separator. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the organic substance is present inside or on the surface of either or both of the positive electrode and the negative electrode. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the nonaqueous electrolyte is in a gel form.   The assembled battery formed by connecting the nonaqueous electrolyte secondary battery of any one of Claims 1-8 in multiple numbers.