JP2009054469A - Non-aqueous secondary battery - Google Patents

Abstract

In a non-aqueous electrolyte battery using an olivine-based positive electrode, when graphite is used as a negative electrode active material, the lithium (Li) insertion reaction into the graphite is slow, so that the battery is rapidly charged at a high rate of current. There is a problem that polarization at the time of the charging reaction is increased and a sufficient charge capacity cannot be obtained, or lithium (Li) is deposited on the graphite of the negative electrode active material and cycle characteristics are deteriorated. . The subject of this invention is providing the nonaqueous electrolyte battery which solves such a subject produced in the negative electrode side in the battery which has an olivine type positive electrode, and has the outstanding battery characteristic.
A non-aqueous electrolyte battery comprising a positive electrode including a lithium metal phosphate compound having an olivine-type crystal structure, a negative electrode using a negative electrode active material capable of doping and dedoping lithium, and a non-aqueous electrolyte. A non-aqueous electrolyte battery comprising inorganic oxide nanoparticles in the negative electrode active material.
[Selection] Figure 1

Description

  The present invention relates to a negative electrode for a non-aqueous electrolyte secondary battery excellent in discharge characteristics at low cost, long life, and large current.

At present, lithium-ion non-aqueous electrolyte secondary batteries with high output and high energy density are widely used due to miniaturization and high performance of mobile phones and notebook computers. Such a lithium ion non-aqueous electrolyte secondary battery generally includes a positive electrode using LiCoO ₂ as a positive electrode active material, a negative electrode using lithium metal, a lithium alloy, or a carbon material capable of occluding and releasing lithium, ethylene carbonate ( An electrolytic solution in which an electrolyte made of a lithium salt such as LiBF ₄ or LiPF ₆ is dissolved in an organic solvent such as EC) or diethyl carbonate (DEC) is used.

However, cobalt (Co) used for the positive electrode active material LiCoO ₂ is a scarce resource and has a limited amount of reserves, resulting in high production costs. For this reason, the use of LiMn ₂ O ₄ , LiNiO ₂ or the like as a positive electrode active material replacing LiCoO ₂ has been studied. However, when LiMn ₂ O ₄ is used as the positive electrode active material, it is difficult to obtain a sufficient discharge capacity, and when the battery temperature increases, there are problems such as dissolution of Mn in this LiMn ₂ O _4. It was. Further, when LiNiO ₂ is used as the positive electrode active material, there are problems such as a low discharge voltage.

In addition, in the case of a non-aqueous electrolyte secondary battery using LiCoO ₂ as the positive electrode active material, there is a problem that the thermal stability is extremely lowered at a high temperature in a charged state. For this problem, the use of olivine type lithium phosphate as a positive electrode active material has been studied (see Patent Document 1). Here, the olivine-type lithium phosphate is a lithium composite compound represented by a general formula LiMPO ₄ (M is at least one element selected from Mn, Co, Ni, Mg, Zn, Cr, Ti, and V). It is.

A positive electrode using olivine-type lithium phosphate (hereinafter referred to as an olivine-based positive electrode) and phosphoric acid (PO ₄ ) form a stable skeletal structure, which is very excellent in thermal stability in a charged state. Very safe. The operating voltage varies depending on the type of metal element M serving as a nucleus, and the battery voltage can be arbitrarily selected by selecting M. Further, the theoretical capacity is relatively high at about 140 to 170 mAh / g, and extremely high-efficiency charging / discharging is possible. Further, by selecting an inexpensive metal that is produced in large quantities as the metal element M, the production cost can be greatly reduced.

  Usually, in a lithium ion battery, a part of the electrolytic solution reacts at the time of first charge, and a solid electrolyte film (SEI: Solid Electrolyte Interface) of several nm is formed on the negative electrode surface. By adding inorganic oxide nanoparticles in the negative electrode active material layer, inorganic oxide nanoparticles are present in the SEI coating. This speeds up the insertion and desorption of Li into the negative electrode active material, increases the charge / discharge capacity, and significantly improves the load characteristics.

JP 2006-12544 A

  In a battery having an olivine-based positive electrode as described above, when a carbon material is used as the negative electrode active material, the lithium (Li) insertion reaction into the carbon material is slow, so that the battery is rapidly charged at a high rate of current. In this case, there is a problem that polarization at the time of the charging reaction is increased and a sufficient charging capacity cannot be obtained, or Li is deposited on the carbon material of the negative electrode active material, resulting in deterioration of cycle characteristics.

  Accordingly, an object of the present invention is to solve such a problem that occurs on the negative electrode side in a battery having an olivine-based positive electrode and to provide a nonaqueous electrolyte battery having excellent battery characteristics.

  In order to solve the above problems, the present invention provides a positive electrode containing a lithium metal phosphate compound having an olivine type crystal structure, a negative electrode using a negative electrode active material capable of doping and dedoping lithium, and a non-aqueous electrolyte. A nonaqueous electrolyte battery comprising a negative electrode active material containing inorganic oxide nanoparticles.

  According to the non-aqueous electrolyte battery of the present invention, by combining a positive electrode made of a positive electrode active material having an olivine type crystal structure and a negative electrode to which inorganic oxide nanoparticles are added, olivine is improved in acceptability of Li to the negative electrode. It is possible to suppress the Li deposition on the negative electrode surface during rapid charging, which is a problem of the battery having the system positive electrode, and to obtain dramatic improvement in cycle characteristics under high load. As a result, it is possible to provide a battery that is suitable for power tools, electric vehicles, and the like, has a high output, a long life, and is low in cost and environmental load.

In addition, when using an inorganic oxide nanoparticle-added negative electrode and a positive electrode made of a positive electrode active material having no olivine type crystal structure, although the charge capacity at a low rate slightly increases, the effect of improving load characteristics is I can hardly get it. This is because a positive electrode active material such as LiCoO ₂ has a lower thermal stability than an active material having an olivine type crystal structure, so that the structure is increased due to a temperature increase associated with charge and discharge at a high load of 5C and 10C. This is thought to be unstable. In the non-aqueous electrolyte battery of the present invention, by combining a negative electrode to which inorganic oxide nanoparticles are added and a positive electrode made of a positive electrode active material having an olivine crystal structure, extremely high efficiency charge / discharge even at high load And a battery system with significantly improved safety can be achieved.

  Moreover, this invention limits the addition amount of the inorganic oxide nanoparticle to a negative electrode to 0.1-2.0 weight part with respect to 100 weight part of negative electrode active materials, and optimizes a particle size to 30 nm or less. Thus, a dramatic improvement in battery characteristics is achieved. In addition, the advantages of the high-rate, high-efficiency charge / discharge of the olivine-based positive electrode active material used for the positive electrode can be fully exploited, and the battery can be used for power tools such as electric drills and electric vehicles. High output and large size are possible.

(1) First embodiment
(1-1) Configuration of Nonaqueous Electrolyte Secondary Battery FIG. 1 shows a cross-sectional structure of a secondary battery according to the first embodiment of the present invention. This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 21 and a negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. have. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14, and a heat sensitive resistance element (PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. Although not shown, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A.

  The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

  The positive electrode active material layer 21B uses a lithium metal phosphate compound having an olivine structure represented by the following formula (1). The positive electrode active material layer 21B may further contain one or more other positive electrode active materials.

_{LiFe 1-y M y PO 4} ··· (1)
In the formula, M is at least one metal selected from manganese (Mn), cobalt (Co), nickel (Ni), magnesium (Mg), zinc (Zn), chromium (Cr), titanium (Ti), and vanadium (V). Element, 0 ≦ y ≦ 0.8.

  The negative electrode 12 has, for example, a structure in which a negative electrode mixture layer 12B is provided on both surfaces of a negative electrode current collector 12A having a pair of surfaces. As shown in FIG. 5, the negative electrode 12 has a rectangular electrode portion and a current collector exposed portion 12C extending from one side of the electrode portion. This current collector exposed portion 12C is not provided with the negative electrode mixture layer 12B, and the negative electrode current collector 12A is exposed. The current collector exposed portion 12 is electrically connected to the negative electrode lead 4. Although not shown, the negative electrode mixture layer 12B may be provided only on one surface of the negative electrode current collector 12A. The negative electrode current collector 12A is made of, for example, a metal foil such as a copper foil.

  The negative electrode mixture layer 12B contains one or more negative electrode active materials capable of inserting and extracting lithium (Li) as a negative electrode active material, and a conductive aid such as graphite as necessary. And a polymer binder such as polyvinylidene fluoride.

  In this nonaqueous electrolyte secondary battery, the electrochemical equivalent of the negative electrode 12 capable of occluding and releasing lithium (Li) is larger than the electrochemical equivalent of the positive electrode 11, and the negative electrode is charged during charging. No lithium metal is deposited on the substrate 12.

  Examples of the negative electrode active material capable of inserting and extracting lithium include non-graphitizable carbon, graphitizable carbon, artificial graphite, amorphous alloy-carbon composite materials, graphite, pyrolytic carbons, and cokes. , Glassy carbons, organic polymer compound fired bodies, carbon materials such as carbon fiber or activated carbon, among which non-graphitizable carbon, graphitizable carbon, artificial graphite, and amorphous alloy-carbon composite materials. preferable. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body refers to a carbonized material obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as: Examples of the polymer material include polyacetylene and polypyrrole.

  These carbon materials are preferable because the change in the crystal structure that occurs during charge / discharge is very small, a high charge / discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Further, non-graphitizable carbon is preferable because excellent characteristics can be obtained. Furthermore, a battery having a low charge / discharge potential, specifically, a battery having a charge / discharge potential close to that of lithium metal is preferable because a high energy density of the battery can be easily realized.

  The negative electrode active material preferably further contains vapor grown carbon fiber (hereinafter referred to as VGCF). The amount of VGCF added is preferably 0.1 to 5 parts by weight and more preferably 0.5 to 1 part by weight with respect to 100 parts by weight of the negative electrode active material. VGCF preferably has a hollow structure inside, a fiber diameter of 2 to 1000 nm, and an aspect ratio of 10 to 15000. This is because by using VGCF having such a structure, the conductivity between the negative electrode active materials can be increased, and the cycle characteristics can be improved by increasing the charge / discharge capacity and suppressing Li deposition. Also, if the addition amount is too small, the effect of improving the conductivity cannot be sufficiently obtained. Conversely, if the addition amount is excessively increased, the dispersion state is deteriorated or the irreversible capacity accompanying the first charge / discharge is increased. . If the fiber diameter is too small, paint properties are deteriorated. If the fiber diameter is too large, contact between the negative electrode active materials is hindered. Therefore, the above range of addition amount and fiber diameter is preferable. Here, the “aspect ratio” is the ratio of the length of a two-dimensional object.

  The negative electrode active material capable of inserting and extracting lithium can also store and release lithium (Li), and includes at least one of a metal element and a metalloid element as a constituent element Materials are also mentioned. This is because a high energy density can be obtained by using such a material. In particular, the use with a carbon material is more preferable because a high energy density can be obtained and excellent cycle characteristics can be obtained. This negative electrode active material may be a single element or an alloy or a compound of a metal element or a metalloid element, or may have one or more of these phases at least in part. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. Some of the structures include a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them.

  Examples of the metal element or metalloid element constituting the negative electrode active material include magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium ( Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium ( Pd) or platinum (Pt). These may be crystalline or amorphous.

  Among these, as the negative electrode active material, a material containing a 4B group metal element or a semimetal element in the short-period periodic table as a constituent element is preferable, and at least one of silicon (Si) and tin (Sn) is particularly preferable. It is included as a constituent element. This is because silicon (Si) and tin (Sn) have a large ability to occlude and release lithium (Li), and a high energy density can be obtained.

  As an alloy of tin (Sn), for example, as a second constituent element other than tin (Sn), silicon (Si), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr) The thing containing at least 1 sort is mentioned. As an alloy of silicon (Si), for example, as a second constituent element other than silicon (Si), tin (Sn), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr). The thing containing 1 type is mentioned.

  Examples of the tin (Sn) compound or silicon (Si) compound include those containing oxygen (O) or carbon (C). In addition to tin (Sn) or silicon (Si), the above-described compounds are used. Two constituent elements may be included.

Examples of the negative electrode active material capable of inserting and extracting lithium (Li) further include other metal compounds or polymer materials. Examples of other metal compounds include oxides such as MnO ₂ , V ₂ O ₅ , and V ₆ O ₁₃ , sulfides such as NiS and MoS, and lithium nitrides such as LiN ₃ , and polymer materials include polyacetylene. , Polyaniline or polypyrrole.

The negative electrode active material includes inorganic oxide nanoparticles. Here, the “nanoparticle” is generally an ultrafine particle having a particle diameter of about 1 to 100 nm. The median particle size of the inorganic oxide nanoparticles is 30 nm or less, preferably 15 nm or less. By setting the particle size of the inorganic oxide nanoparticles to 30 nm or less, the inorganic oxide can be present in the SEI film without inhibiting the diffusion of lithium ions. Improved properties can be achieved. When the median particle size of the inorganic oxide nanoparticles is larger than 30 nm, uniform dispersion cannot be obtained, or the particle size greatly exceeds the SEI coating, resulting in an insulator, resulting in a decrease in conductivity. There is a fear. The inorganic oxide particles have a specific surface area of approximately 30 m ² / g or more when the median diameter is 30 nm or less, and a specific surface area of 100 m ² / g or more when the median particle diameter is 15 nm or less.

  Here, the “median particle diameter” is a diameter in which when the powder is divided into two from a certain particle diameter, the larger side and the smaller side are equivalent. The “specific surface area” is a value measured by the BET method using nitrogen gas.

  The content of the inorganic oxide nanoparticles in the negative electrode is preferably 0.1 to 2 parts by weight and more preferably 0.5 to 1 part by weight with respect to 100 parts by weight of the negative electrode active material. When the addition amount of the inorganic oxide nanoparticles is less than 0.1 parts by weight with respect to 100 parts by weight of the negative electrode active material, the surface of the active material cannot be sufficiently covered and the effect cannot be sufficiently exerted. On the other hand, when the addition amount is more than 2 parts by weight, the content of the active material contributing to the battery capacity in the electrode mixture is reduced, and the battery capacity is reduced. Therefore, a marked improvement in battery characteristics can be obtained by setting the amount of the inorganic oxide nanoparticles to be in the range of 0.1 to 2 parts by weight with respect to 100 parts by weight of the negative electrode active material.

As the inorganic oxide nanoparticles, for example, Al ₂ O ₃ , SiO ₂ , ZrO ₂ and TiO ₂ are preferably mentioned. Among them, the effect of increasing the charge / discharge capacity and improving the load characteristics is great, and it is easy to obtain and cost. Al ₂ O ₃ and SiO ₂ are preferable because they are cheap.

  The separator 23 is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more porous films are laminated. May be. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the battery due to the shutdown effect.

  The electrolytic solution includes, for example, a solvent made of a nonaqueous solvent such as an organic solvent and an electrolyte salt dissolved in the solvent. As the non-aqueous solvent, cyclic carbonates such as ethylene carbonate or propylene carbonate can be used, and it is preferable to use one of ethylene carbonate and propylene carbonate, in particular, a mixture of both. This is because the cycle characteristics can be improved.

  Further, as the non-aqueous solvent, it is preferable to use a mixture of chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, or methyl propyl carbonate in addition to these cyclic carbonates. This is because high ionic conductivity can be obtained.

  Furthermore, the non-aqueous solvent preferably contains 2,4-difluoroanisole or vinylene carbonate. This is because 2,4-difluoroanisole can improve discharge capacity, and vinylene carbonate can improve cycle characteristics. Therefore, it is preferable to use a mixture of these because the discharge capacity and cycle characteristics can be improved.

  In addition to these, non-aqueous solvents include butylene carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1, 3-dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropironitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N -Dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide or trimethyl phosphate.

  A compound obtained by substituting at least a part of hydrogen in these non-aqueous solvents with fluorine may be preferable because the reversibility of the electrode reaction may be improved depending on the type of electrode to be combined.

As electrolyte salt, lithium salt is mentioned, for example, 1 type may be used independently, and 2 or more types may be mixed and used for it. Lithium salts include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, difluoro [oxolato-O, O ′] lithium borate, lithium bisoxalate borate, or LiBr. Among them, LiPF ₆ is preferable because it can obtain high ion conductivity and can improve cycle characteristics.

(1-2) Manufacturing Method of Nonaqueous Electrolyte Secondary Battery The nonaqueous electrolyte secondary battery configured as described above can be manufactured, for example, as follows.

  First, for example, the positive electrode active material layer 21B is formed on the positive electrode current collector 21A to produce the positive electrode 21. The positive electrode active material layer 21B is prepared, for example, by mixing a positive electrode active material, a conductive agent, and a binder to prepare a positive electrode mixture, and then using the positive electrode mixture in a solvent such as N-methyl-2-pyrrolidone. It is formed by dispersing to form a paste-like positive electrode mixture slurry, applying this positive electrode mixture slurry to the positive electrode current collector 21A, drying the solvent, and compression molding with a roll press or the like.

  Further, for example, the negative electrode active material layer 22B is formed on the negative electrode current collector 22A to produce the negative electrode 22. The negative electrode active material layer 22B may be formed by, for example, any one of a vapor phase method, a liquid phase method, a baking method, and coating, or a combination of two or more thereof. When formed by a vapor phase method, a liquid phase method, or a firing method, the negative electrode active material layer 22B and the negative electrode current collector 22A may be alloyed at least at a part of the interface at the time of formation. An alloy may be formed by heat treatment under a non-oxidizing atmosphere.

  As the vapor phase method, for example, a physical deposition method or a chemical deposition method can be used. Specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a thermal CVD (Chemical Vapor Deposition). A chemical vapor deposition method, a plasma CVD method, and the like can be used. As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. Known methods can also be used for the firing method. For example, an atmospheric firing method, a reactive firing method, and a hot press firing method can be used. In the case of application, it can be formed in the same manner as the positive electrode 21.

  Subsequently, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through the gasket 17. Thereby, the secondary battery shown in FIGS. 1 and 2 is formed.

  In this secondary battery, when charged, lithium ions are released from the positive electrode active material layer 21B, and the negative electrode material that can occlude and release lithium contained in the negative electrode active material layer 22B via the electrolytic solution. Occluded. Next, when discharging is performed, lithium ions stored in the negative electrode material capable of inserting and extracting lithium in the negative electrode active material layer 22B are released, and are inserted into the positive electrode active material layer 21B through the electrolytic solution. .

(2) Second Embodiment (2-1) Configuration of Nonaqueous Electrolyte Secondary Battery Next, the configuration of the secondary battery according to the second embodiment of the present invention will be described with reference to FIGS. .

  FIG. 3 is an exploded perspective view showing an example of the configuration of the secondary battery according to the second embodiment of the present invention. As shown in FIG. 3, this non-aqueous electrolyte secondary battery has a battery element 31 to which a positive electrode lead 33 and a negative electrode lead 34 are attached housed in a film-like exterior member 32, and is reduced in size and weight. Can be made thinner and thinner.

  Each of the positive electrode lead 33 and the negative electrode lead 34 is led out from the inside of the exterior member 32 to the outside, for example, in the same direction. Each of the positive electrode lead 33 and the negative electrode lead 34 is made of a metal material such as aluminum (Al), copper (Cu), nickel (Ni), or stainless steel, and has a thin plate shape or a mesh shape.

  The exterior member 32 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. The exterior member 32 is disposed, for example, so that the polyethylene film side and the battery element 31 face each other, and the outer edge portions are in close contact with each other by fusion or an adhesive. Although not shown, an adhesive film for preventing the entry of outside air is inserted between the exterior member 32 and the positive electrode lead 33 and the negative electrode lead 34. The adhesion film is made of a material having adhesion to the positive electrode lead 33 and the negative electrode lead 34, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene. The exterior member 32 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 4 is a perspective view showing an example of the appearance of the battery element 31. FIG. 5 is a cross-sectional view showing an example of the configuration of the battery element 31. As shown in FIGS. 4 and 5, the battery element 31 is a laminated electrode body in which a positive electrode 41 and a negative electrode 42 are laminated via a separator 43, and the separator 43 is impregnated with an electrolytic solution that is a liquid electrolyte. Has been.

  The positive electrode 41 has, for example, a structure in which a positive electrode mixture layer 41B is provided on both surfaces of a positive electrode current collector 41A having a pair of surfaces. As shown in FIG. 6, the positive electrode 41 includes a rectangular electrode portion and a current collector exposed portion 41 </ b> C extending from one side of the electrode portion. The positive electrode mixture layer 41B is not provided in the current collector exposed portion 41C, and the positive electrode current collector 41A is exposed. The current collector exposed portion 41 is electrically connected to the positive electrode lead 3. Although not shown, the positive electrode mixture layer 41B may be provided only on one surface of the positive electrode current collector 41A. The positive electrode current collector 41A is made of, for example, a metal foil such as an aluminum foil.

  The negative electrode 42 has, for example, a structure in which a negative electrode mixture layer 42B is provided on both surfaces of a negative electrode current collector 42A having a pair of surfaces. As shown in FIG. 7, the negative electrode 42 includes a rectangular electrode portion and a current collector exposed portion 42 </ b> C extending from one side of the electrode portion. The current collector exposed portion 42C is not provided with the negative electrode mixture layer 42B, and the negative electrode current collector 42A is exposed. The current collector exposed portion 42 is electrically connected to the negative electrode lead 34. Although not shown, the negative electrode mixture layer 42B may be provided only on one surface of the negative electrode current collector 42A.

  As shown in FIG. 8, the separator 53 has a rectangular shape or the like, is electrically stable, is chemically stable to a positive electrode active material, a negative electrode active material, or a solvent, and is electrically conductive. Any material may be used as long as it does not have sex. For example, a polymer nonwoven fabric, a porous film, glass or ceramic fibers in a paper shape can be used, and a plurality of these may be laminated. In particular, a porous polyolefin film is preferably used, and a composite of this with a heat-resistant material made of polyimide, glass, ceramic fibers, or the like may be used.

(2-2) Manufacturing Method of Nonaqueous Electrolyte Secondary Battery The nonaqueous electrolyte secondary battery configured as described above can be manufactured, for example, as follows.

  The positive electrode 41 is produced as follows. First, for example, a positive electrode active material, an inorganic oxide that does not contribute to charging / discharging, a binder, and a conductive additive are mixed to prepare a positive electrode mixture, and this positive electrode mixture is mixed with N-methylpyrrolidone or the like. A paste-like positive electrode mixture paint is prepared by dispersing in a solvent. Next, this is applied to both surfaces of the positive electrode current collector 41A, dried, and then pressed to form the positive electrode mixture layer 41B. Thereafter, this is cut into the shape shown in FIG.

  The negative electrode 42 is produced as follows. First, for example, a negative electrode active material, a binder, and a conductive additive are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methylpyrrolidone to obtain a paste-like negative electrode mixture. An agent paint is prepared. Next, this is applied to both surfaces of the negative electrode current collector 42A, dried, and then pressed to form the negative electrode mixture layer 42B. Thereafter, this is cut into the shape shown in FIG.

  The battery element 31 is produced as follows. First, a polypropylene microporous film or the like is cut into the shape shown in FIG. Next, the plurality of negative electrodes 42, positive electrodes 41, and separators 43 obtained as described above are, for example, as shown in FIG. 4, negative electrodes 42, separators 43, positive electrodes 41,. 43 and the negative electrode 42 are laminated in this order to produce a battery element.

  Next, the current collector exposed portion 41 </ b> C of the positive electrode 41 is welded to the positive electrode lead 33. Similarly, the current collector exposed portion 42 </ b> C of the negative electrode 42 is welded to the negative electrode lead 34. Next, after the battery element 31 is impregnated with the electrolytic solution, the battery element 31 is sandwiched between the exterior members 32, and the outer edges of the exterior member 32 are brought into close contact with each other by thermal welding or the like. At that time, the positive and negative electrode leads 33 and the negative electrode lead 34 are made to come out of the exterior member 32 through the heat-sealed portion, and these are used as positive and negative electrode terminals. As described above, a nonaqueous electrolyte secondary battery having a target capacity of, for example, 1 Ah can be obtained.

  In the second embodiment of the present invention, the same effect as in the first embodiment described above can be obtained.

(3) Third Embodiment Next, a third embodiment of the present invention will be described. The nonaqueous electrolyte secondary battery according to the third embodiment uses a gel electrolyte layer in place of the electrolyte solution that is a liquid electrolyte in the secondary battery of the second embodiment. In addition, the same code | symbol is attached | subjected to the part similar to the above-mentioned 2nd Embodiment, and the description is abbreviate | omitted.

(3-1) Configuration of Nonaqueous Electrolyte Secondary Battery FIG. 9 is a cross-sectional view showing an example of the configuration of a battery element used in the nonaqueous electrolyte secondary battery according to the second embodiment. The battery element 41 is formed by laminating a positive electrode 41 and a negative electrode 42 with a separator 43 and an electrolyte layer 44 interposed therebetween.

  The electrolyte layer 44 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte layer 44 is preferable because high ion conductivity can be obtained and battery leakage can be prevented. The configuration of the electrolytic solution (that is, the solvent and the electrolyte salt) is the same as that of the nonaqueous electrolyte secondary battery according to the second embodiment.

  Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, and polysiloxane. , Polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene and polycarbonate. In particular, from the viewpoint of electrochemical stability, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, and polyethylene oxide are preferable.

(3-2) Nonaqueous electrolyte secondary battery manufacturing method The nonaqueous electrolyte secondary battery configured as described above can be manufactured, for example, as follows.

  First, a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent is applied to each of the positive electrode 41 and the negative electrode 42, and the mixed solvent is volatilized to form the electrolyte layer 44. In the subsequent steps, a nonaqueous electrolyte secondary battery can be obtained in the same manner as in the second embodiment except that the positive electrode 41 and the negative electrode 42 on which the electrolyte layer 14 is formed are used.

  In the third embodiment of the present invention, the same effect as in the second embodiment described above can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

In the following examples and comparative examples, the particle size of the inorganic oxide nanoparticles added to the negative electrode active material was measured by the following method.
Particle size: The particle size of the inorganic oxide nanoparticles was measured by the static light scattering method (HORIBA LA-910).

1. Evaluation by Coin Cell First, in order to confirm the effect of the difference in the negative electrode, a positive electrode was made of LiFePO ₄ to produce a coin cell, and battery characteristics were evaluated. The battery was produced according to the following procedure.

<Example 1-1>
As a negative electrode active material, 100 parts by weight of artificial graphite having a median particle diameter of 21.5 μm and 0.1 part by weight of Al ₂ O ₃ having a median particle diameter of 13 nm were mixed. 95 parts by weight of the mixture, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone not included in the amount are kneaded and mechanically stirred by a mixer to mix negative electrodes with a predetermined viscosity. A material paint was obtained. The negative electrode mixture paint was applied to a 12 μm copper (Cu) foil, dried and pressed to form a negative electrode mixture layer having a predetermined thickness. Using a punching machine, punching was performed to a predetermined diameter to obtain a coin cell negative electrode.

A positive electrode was prepared by applying a positive electrode mixture paint containing a positive electrode active material LiFePO ₄ to a 15 μm aluminum foil. In addition, in order to prevent leakage of the electrolyte, a gasket was attached to the outside. A negative electrode current collector carrying a negative electrode composite material layer is placed on a copper negative electrode can, and LiPF ₆ is added at 1 mol / dm ^{3 in} a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). A dissolved non-aqueous electrolyte was injected. A polypropylene separator having a thickness of 25 μm was placed thereon, and an electrolytic solution was further injected, followed by covering with a counter electrode. Then, the coin cell was produced by mechanically pressing and crimping and sealing.

<Examples 1-2 to 1-5>
Except that Al ₂ O ₃ having a median particle diameter of 13 nm and VGCF (fiber diameter: 150 nm, aspect ratio: 60) were added to the negative electrode active material at a weight ratio shown in Table 1, the same conditions as in Example 1-1 were used. A coin cell was produced.

<Example 1-6>
A coin cell was produced under the same conditions as in Example 1-1 except that Al ₂ O ₃ having a median particle size of 28 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 1-1>
95 parts by weight of artificial graphite having a median particle diameter of 21.5 μm as a negative electrode active material, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone not included in the quantity are kneaded and machined by a mixer To obtain a negative electrode mixture paint having a predetermined viscosity. Other than that, the coin cell was produced on the same conditions as Example 1-1.

<Comparative Examples 1-2 to 1-3>
A coin cell was manufactured under the same conditions as in Example 1-1 except that Al ₂ O ₃ having a median particle size of 13 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 1-4>
A coin cell was produced under the same conditions as Example 1-1 except that Al ₂ O ₃ having a median particle diameter of 1 μm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 1-5>
A coin cell was produced under the same conditions as in Example 1-1 except that VGCF (fiber diameter: 150 nm, aspect ratio: 60) was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 1-6>
A coin cell was produced under the same conditions as Example 1-1 except that Al ₂ O ₃ having a median particle diameter of 50 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Examples 2-1 to 2-5>
The inorganic oxide added to the negative electrode active material was changed to TiO ₂ having a median particle diameter of 21 nm, and TiO ₂ and VGCF (fiber diameter: 150 nm, aspect ratio: 60) were added at a weight ratio shown in Table 1, A coin cell was manufactured under the same conditions as in Example 1-1.

<Example 2-6>
A coin cell was produced under the same conditions as in Example 1-1 except that TiO ₂ having a median particle size of 30 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Examples 2-1 to 2-3>
The coin cell was changed under the same conditions as in Example 1-1, except that the inorganic oxide added to the negative electrode active material was changed to TiO ₂ having a median particle diameter of 21 nm and the addition amount of TiO _{2 was} added at a weight ratio shown in Table 1. Was made.

<Comparative Example 2-4>
A coin cell was produced under the same conditions as Example 1-1 except that TiO ₂ having a median particle size of 1.5 μm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 2-5>
A coin cell was produced under the same conditions as in Example 1-1 except that VGCF (fiber diameter: 150 nm, aspect ratio: 60) was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 1-6>
A coin cell was produced under the same conditions as Example 1-1 except that TiO ₂ having a median particle size of 53 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Examples 3-1 to 3-5>
The inorganic oxide added to the negative electrode active material is changed to ZrO ₂ having a median particle diameter of 20 nm, and ZrO ₂ and VGCF (fiber diameter: 150 nm, aspect ratio: 60) are added to the artificial graphite at a weight ratio shown in Table 1. A coin cell was manufactured under the same conditions as in Example 1-1 except that.

<Example 3-6>
A coin cell was produced under the same conditions as Example 1-1 except that ZrO ₂ having a median particle size of 30 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Examples 3-1 to 3-3>
The inorganic oxide to be added to the negative electrode active material, instead of the ZrO ₂ having a median particle size of 20 nm, except that ZrO ₂ was added to the negative electrode active material in a weight ratio shown in Table 1, the same conditions as in Example 1-1 A coin cell was produced.

<Comparative Example 3-4>
A coin cell was produced under the same conditions as in Example 1-1 except that ZrO ₂ having a median particle diameter of 1 μm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 3-5>
A coin cell was produced under the same conditions as in Example 1-1 except that VGCF (fiber diameter: 150 nm, aspect ratio: 60) was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 3-6>
A coin cell was produced under the same conditions as Example 1-1 except that ZrO ₂ having a median particle size of 54 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Examples 4-1 to 4-5>
The inorganic oxide added to the negative electrode active material is changed to SiO ₂ having a median particle diameter of 7 nm, and SiO ₂ and VGCF (fiber diameter: 150 nm, aspect ratio: 60) are added to the negative electrode active material in the weight ratio shown in Table 1. A coin cell was manufactured under the same conditions as in Example 1-1 except that.

<Example 4-6>
A coin cell was produced under the same conditions as in Example 1-1 except that SiO ₂ having a median particle size of 27 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Examples 4-1 to 4-3>
The inorganic oxide to be added to the negative electrode active material was changed to SiO ₂ of median particle size 7 nm, except that SiO ₂ was added to the negative electrode active material in a weight ratio shown in Table 1, the same conditions as in Example 1-1 A coin cell was produced.

<Comparative Example 4-4>
A coin cell was produced under the same conditions as in Example 1-1 except that SiO ₂ having a median particle size of 1.3 μm was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 4-5>
A coin cell was produced under the same conditions as in Example 1-1 except that VGCF (fiber diameter: 150 nm, aspect ratio: 60) was added to the negative electrode active material at a weight ratio shown in Table 1.

<Comparative Example 4-6>
A coin cell was produced under the same conditions as Example 1-1 except that SiO ₂ having a median particle size of 48 nm was added to the negative electrode active material at a weight ratio shown in Table 1.

(Evaluation)
The coin cells produced in Examples 1-1 to 4-5 and Comparative Examples 1-1 to 4-6 were evaluated under the following conditions.
Charging: After charging at a constant current of 0.2 C until the battery voltage reached 3.6 V, charging was terminated when the current value was 0.04 mA or less at a constant voltage of 3.6 V.
Discharge: The constant current was changed from 0.2 C to 5 C, and when the voltage reached 2 V, the discharge was stopped.

From the battery capacity measured under the above conditions, the maintenance ratio of the 5C discharge capacity with respect to the 0.2C discharge capacity was calculated by [Equation 1]. The results are shown in Table 1.
Discharge capacity retention ratio = {(5C discharge capacity / 0.2C discharge capacity) × 100}% [Formula 1]

As can be seen from Table 1, when Examples 1-1 to 1-4 in which 0.1 to 2 wt% of inorganic oxide nanoparticles were added to the negative electrode active material were compared with Comparative Example 1-1 in which the inorganic oxide nanoparticles were not added, The discharge capacity was greatly improved by adding inorganic oxide nanoparticles (Al ₂ O ₃ ) to the negative electrode active material. In addition, the discharge capacity retention rate was dramatically improved to around 90%, and good load characteristics were exhibited. This is considered to be because the diffusibility of lithium ions on the surface of the negative electrode active material was improved by including the inorganic oxide nanoparticles in the negative electrode active material.

  In Comparative Example 1-2, the effect was insufficient because the amount of inorganic oxide nanoparticles added to the negative electrode active material was as small as 0.05 wt%. On the contrary, it turned out that an effect will reduce when the addition amount of an inorganic oxide nanoparticle is too much with 3 wt% like Comparative Example 1-3. This is because the inorganic oxide, which is an insulator, covers the surface of the negative electrode active material too much, and the resistance increases. It was thought that the adhesion strength was inferior and the conductivity decreased. In addition, from these facts, when the content of the inorganic oxide nanoparticles in the negative electrode active material is in the range of 0.1 to 2 parts by weight with respect to 100 parts by weight of the negative electrode active material, the discharge capacity is dramatically increased. It has been found that the effect of improving the load characteristics is exhibited.

  From Comparative Example 1-4, it was found that when inorganic oxide nanoparticles having a large particle size of 1 μm were added to the negative electrode active material, both the discharge capacity and the discharge capacity retention rate were reduced. Moreover, from Comparative Example 1-6, it was found that the increase in discharge capacity was small when the particle size was 50 nm. Furthermore, from Example 1-5, the discharge capacity retention rate could be further improved by adding inorganic oxide nanoparticles and VGCF to the negative electrode active material. This was thought to be due to the synergistic effect of accelerating lithium ion diffusion on the surface of the negative electrode active material by the inorganic oxide nanoparticles and improving the conductivity between the active material particles by VGCF. Further, from Comparative Example 1-5 in which only VGCF was added without adding inorganic oxide nanoparticles to the negative electrode active material, the effect of improving the discharge capacity retention rate was insufficient only by adding VGCF to the negative electrode active material. It turns out that.

From Examples 2-1 to 4-5 and Comparative Examples 2-1 to 4-6, when adding other inorganic oxide nanoparticles such as TiO ₂ , ZrO ₂ , and SiO ₂ to the negative electrode active material, Al It was found that ₂ O ₃ had the same effect as described above. Further, from Examples 1-5, 2-5, 3-5, 4-5 and 5-5 and Comparative Examples 1-4, 2-4, 3-4 and 4-4, inorganic added to the negative electrode active material It turned out that a favorable result is obtained by making the particle size of an oxide nanoparticle into 30 nm or less.

2. Evaluation by Cylindrical Battery Next, a cylindrical non-aqueous electrolyte secondary battery was fabricated using a positive electrode using an olivine-based positive electrode active material and a negative electrode to which inorganic oxide nanoparticles were added, and battery characteristics were obtained. Was evaluated. A method for manufacturing a cylindrical battery will be described below. However, the present invention is not limited to the form of the manufacturing method described below.

<Example 5-1>
First, 90 parts by weight of LiFePO ₄ having a median particle size of 1 μm, to which a minute amount of fine particle carbon has been added in advance as a positive electrode active material, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder, a conductive assistant (carbon black) ) 5 parts by weight and N-methylpyrrolidone not included in the amount were kneaded with a mixer to prepare a positive electrode paint. This positive electrode paint was uniformly applied to both surfaces of a positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 15 μm, dried, and compression-molded with a roll press to form the positive electrode active material layer 21B, thereby producing the positive electrode 21. After that, an aluminum positive electrode lead 25 was attached to one end of the positive electrode current collector 21A.

Further, as a negative electrode active material, 100 parts by weight of artificial graphite having a median particle diameter of 21.5 μm and 0.5 part by weight of Al ₂ O ₃ were mixed. 95 parts by weight of the mixture, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone not included in the amount were kneaded. Further, an appropriate amount of N-methylpyrrolidone was added and dispersed so as to obtain a predetermined viscosity, and mechanically mixed with a mixer to obtain a negative electrode mixture paint. This was uniformly applied to both surfaces of a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 12 μm, and heated and press-molded to form a negative electrode active material layer 22B to produce a negative electrode 22. After that, a nickel negative electrode lead 26 was attached to one end of the negative electrode current collector 22A. In addition, the electrochemical equivalent ratio of the positive electrode 21 and the negative electrode 22 was designed so that the capacity | capacitance of the negative electrode 22 was represented by the capacity | capacitance component by occlusion and discharge | release of lithium.

  After each of the positive electrode 21 and the negative electrode 22 was prepared, a microporous separator 23 was prepared, and the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 were laminated in this order, and this laminate was wound many times in a spiral shape to form a jelly roll A spirally wound electrode body 20 was produced.

After producing the wound electrode body 20, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The wound electrode body 20 was housed inside a nickel-plated iron battery can 11. After that, after injecting into the battery can 11 a non-aqueous electrolyte solution in which 1 mol / dm ³ of LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), The battery can 11 was caulked through the gasket 17 to fix the safety valve mechanism 15, the heat sensitive resistance element 16, and the battery lid 14 to obtain a cylindrical secondary battery having an outer diameter of 18 mm and a height of 65 mm.

<Examples 5-2 to 5-3>
A cylindrical battery under the same conditions as in Example 5-1, except that the type and amount of inorganic oxide added to the positive electrode lithium metal phosphate compound or negative electrode active material were changed as shown in Table 2. Was made.

<Comparative Example 5-1>
95 parts by weight of artificial graphite having a median particle size of 21.5 μm as a negative electrode active material, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone not included in the amount were kneaded and mixed with a mixer. To obtain a negative electrode mixture paint having a predetermined viscosity. Otherwise, a cylindrical battery was produced under the same conditions as in Example 5-1.

<Comparative Examples 5-2 to 5-3>
A cylindrical battery under the same conditions as in Example 5-1, except that the type and amount of inorganic oxide added to the positive electrode lithium metal phosphate compound or negative electrode active material were changed as shown in Table 2. Was made.

<Comparative Examples 5-4 to 5-7>
The same conditions as in Example 5-1 except that the positive electrode active material having no olivine type crystal structure was used for the positive electrode, and the type and amount of the inorganic oxide added to the negative electrode were changed as shown in Table 2. A cylindrical battery was produced.

(Evaluation)
The cylindrical batteries produced in Examples 5-1 to 5-3 and Comparative Examples 5-1 to 5-7 were subjected to a charge / discharge test under the following conditions.
Charging: After charging at a constant current of 0.2 C until the battery voltage reached 4.2 V, charging was terminated when the current value became 0.036 mA or less at a constant voltage of 4.2 V.
Discharge: The constant current was changed from 0.2 C to 10 C, and when the voltage reached 2.7 V, the discharge was stopped.

From the battery capacity measured under the above conditions, the maintenance ratio of 10 C discharge capacity with respect to 0.2 C discharge capacity was calculated by [Equation 2]. The results are shown in Table 2.
Discharge capacity retention ratio = (10 C discharge capacity / 0.2 C discharge capacity) × 100}% [Formula 2]

  As can be seen from Table 2, the discharge capacity was maintained at 90% or more by adding inorganic oxide nanoparticles even at a discharge rate of 10 C with a very large capacity.

  Further, from Examples 5-1 to 5-3, the inorganic oxide into the negative electrode active material can be changed even if the type of the metal element of the lithium phosphate compound of the positive electrode is changed or the two lithium metal compounds are mixed. The effect of improving the load characteristics by the addition of was observed.

  Furthermore, in Comparative Examples 5-4 to 5-7 using a positive electrode active material having no olivine type crystal structure, the addition of an inorganic oxide to the negative electrode active material was compared with Examples 5-1 and 5-2. It was found that the effect of improving the load characteristics due to is insufficient. This is thought to be because the thermal stability is inferior to the positive electrode active material having an olivine type crystal structure.

3. Multilayer Battery Next, a multilayer nonaqueous electrolyte secondary battery composed of a positive electrode using an olivine-based positive electrode active material and a negative electrode to which inorganic oxide nanoparticles were added was fabricated, and battery characteristics were obtained. Was evaluated. A method for manufacturing a stacked battery will be described below.

<Example 6-1>
(Production of stacked battery)
First, a positive electrode was produced. 90 parts by weight of LiFePO ₄ having a median particle size of 1 μm, to which a minute amount of fine particle carbon has been added in advance as a positive electrode active material, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and a conductive additive (carbon black) 5 Part by weight and N-methylpyrrolidone not included in the amount were kneaded with a mixer. Further, an appropriate amount of N-methylpyrrolidone was added and dispersed so as to obtain a predetermined viscosity, and mechanically mixed with a mixer to obtain a positive electrode mixture paint. This was applied to both sides of a 15 μm thick aluminum foil, dried to volatilize N-methylpyrrolidone, and then pressed to form a positive electrode mixture layer. This was cut into the shape shown in FIG. 3 to obtain a positive electrode.

Next, a negative electrode was prepared. As a negative electrode active material, 100 parts by weight of artificial graphite having a median particle diameter of 21.5 μm and 0.5 parts by weight of Al ₂ O ₃ were mixed. 95 parts by weight of the mixture, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone not included in the amount are kneaded and mechanically stirred by a mixer to obtain a negative electrode composition having a predetermined viscosity. A material paint was obtained. This was applied to both sides of a 12 μm thick copper foil, dried and then pressed to form a negative electrode mixture layer. This was cut into the shape shown in FIG. 4 to obtain a negative electrode. A polypropylene microporous film having a thickness of 25 μm was cut into the shape shown in FIG. 5 and used as a separator.

  As shown in the cross-sectional view of FIG. 6, nine negative electrodes, eight positive electrodes, and 16 separators obtained by the above operation are viewed from above, as shown in the double-sided negative electrode, separator, double-sided positive electrode, separator, double-sided negative electrode. And a separator, a double-sided coated positive electrode, a separator, a double-sided coated negative electrode, a separator, a double-sided coated positive electrode, a separator, and a double-sided coated negative electrode. In this way, a battery element including six basic laminated units of [positive electrode mixture layer, separator, negative electrode mixture layer] was produced. Note that the negative electrode mixture layers on both ends are isolated and do not function as a battery. The capacity was designed to be about 1050 mAh.

As shown in FIG. 7, three current collector exposed portions of the positive electrode were simultaneously ultrasonically welded to an aluminum current collecting tab. Similarly, four negative electrode collector exposed portions were simultaneously ultrasonically welded to a nickel current collector tab. Non-water in which 1 mol / dm ³ of LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (mixing ratio EC / EMC / DMC / = 35/5/60) An electrolytic solution was injected to impregnate the battery element.

  The battery element was sealed by heat-sealing the opening under reduced pressure using an exterior material made of an aluminum laminate film made of a resin layer, an aluminum layer, and a resin layer. At that time, the positive and negative electrode leads were exposed to the outside of the exterior material through the heat fusion part, and these were used as the positive and negative electrode terminals. FIG. 7 shows a schematic view of the appearance of the stacked battery.

<Examples 6-2 to 6-3>
A laminated type under the same conditions as in Example 6-1 except that the type and amount of inorganic oxide added to the positive electrode lithium metal phosphate compound or negative electrode active material were changed as shown in Table 3. A battery was produced.
<Comparative Example 6-1>
95 parts by weight of artificial graphite having a median particle diameter of 21.5 μm as a negative electrode active material, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone not included in the amount were kneaded and mixed by a mixer. The mixture was mechanically stirred to obtain a negative electrode mixture paint having a predetermined viscosity. Otherwise, a stacked battery was produced under the same conditions as in Example 6-1.

<Comparative Examples 6-2 to 6-3>
A laminated type under the same conditions as in Example 6-1 except that the type and amount of inorganic oxide added to the positive electrode lithium metal phosphate compound or negative electrode active material were changed as shown in Table 3. A battery was produced.

<Comparative Examples 6-4 to 6-7>
Example 6-1 except that the positive electrode active material having no olivine type crystal structure was used as the positive electrode, and the type and amount of the inorganic oxide added to the negative electrode active material were changed as shown in Table 3. A laminated battery was produced under the same conditions.

The charge / discharge test was performed on the stacked batteries produced in Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-7 under the following conditions.
Charging: After charging at a constant current of 0.2 C until the battery voltage reached 4.2 V, charging was terminated when the current value became 0.036 mA or less at a constant voltage of 4.2 V.
Discharge: The constant current was changed from 0.2 C to 10 C, and when the voltage reached 2.7 V, the discharge was stopped.

From the battery capacity measured under the above conditions, the maintenance ratio of 10 C discharge capacity with respect to 0.2 C discharge capacity was calculated by [Equation 3]. The results are shown in Table 3.
Discharge capacity retention ratio = (10 C discharge capacity / 0.2 C discharge capacity) × 100}% [Formula 3]

  As can be seen from Table 3, even in a stacked battery as well as a cylindrical battery, by adding inorganic oxide nanoparticles to the negative electrode active material, even at a discharge rate of 10 C with a very large capacity, 90% or more The discharge capacity was maintained.

  Further, from Examples 6-1 to 6-3, even if the type of the metal element of the lithium phosphate compound of the positive electrode is changed or two types of lithium metal compounds are mixed, the addition of inorganic oxide nanoparticles It was found that the load characteristics were improved.

  Further, in Comparative Examples 6-4 to 6-7 using a positive electrode active material having no olivine type crystal structure, compared with Examples 6-1 and 6-2, inorganic oxide nanoparticles to the negative electrode active material The effect of improving load characteristics due to the addition of was insufficient.

  From the above results, in any form of a coin cell, a cylindrical battery, and a stacked battery, by combining a positive electrode containing a lithium phosphate compound having an olivine crystal structure with a negative electrode to which inorganic oxide nanoparticles are added. The discharge capacity is greatly improved, the discharge capacity maintenance rate at a high rate is dramatically increased to 90% or more, and a large capacity, high efficiency, long life non-aqueous secondary battery with very good load characteristics is provided. I found out that I could do it.

It is sectional drawing showing the structure of the nonaqueous electrolyte secondary battery which concerns on the 1st Embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a disassembled perspective view which shows an example of a structure of the nonaqueous electrolyte secondary battery by the 2nd Embodiment of this invention. It is a perspective view which shows an example of the external appearance of the battery element used for the nonaqueous electrolyte secondary battery by the 2nd Embodiment of this invention. It is sectional drawing which shows an example of a structure of the battery element used for the nonaqueous electrolyte secondary battery by the 2nd Embodiment of this invention. It is a top view which shows an example of the shape of a positive electrode. It is a top view which shows an example of the shape of a negative electrode. It is a top view which shows an example of the shape of a separator. It is sectional drawing which shows an example of a structure of the nonaqueous electrolyte secondary battery by the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Battery cans 12, 13 ... Insulating plate 14 ... Battery cover 15 ... Safety valve mechanism 15A ... Disk board 16 ... Heat sensitive resistance element 17 ... Gasket 20 ... Winding Rotating electrode body 21, 41 ... Positive electrode 21A, 41A ... Positive electrode current collector 21B ... Positive electrode active material layer 22, 42 ... Negative electrode 22A, 42A ... Negative electrode current collector 22B ... Negative electrode Active material layer 23, 43 ... Separator 24 ... Center pin 25, 33 ... Positive electrode lead 26, 34 ... Negative electrode lead
31, 35 ... Battery element 32 ... Exterior member 41B ... Positive electrode mixture layer 42B ... Negative electrode mixture layer 41C, 42 ... Current collector exposed portion 44 ... Electrolyte layer

Claims (6)

A nonaqueous electrolyte battery comprising a positive electrode, a negative electrode using a negative electrode active material capable of doping and dedoping lithium, and a nonaqueous electrolyte,
The positive electrode includes at least a lithium metal phosphate compound having an olivine type crystal structure represented by the following formula (1):
The negative electrode active material includes inorganic oxide nanoparticles,
A non-aqueous electrolyte battery, wherein the inorganic oxide nanoparticles have a median particle size of 30 nm or less.
_{LiFe 1-y M y PO 4} ··· (1)
(In the formula, M is at least one metal element selected from Mn, Co, Ni, Mg, Zn, Cr, Ti, and V, and 0 ≦ y ≦ 0.8.)   2. The nonaqueous electrolyte battery according to claim 1, wherein the content of the inorganic oxide nanoparticles in the negative electrode is 0.1 to 2 parts by weight with respect to 100 parts by weight of the negative electrode active material. The non-aqueous electrolyte battery according to claim 1, wherein the inorganic oxide nanoparticles are at least one of Al ₂ O ₃ , SiO ₂ , ZrO ₂ and TiO ₂ .   2. The nonaqueous electrolyte battery according to claim 1, wherein the negative electrode active material is at least one of non-graphitizable carbon, graphitizable carbon, artificial graphite, and amorphous alloy-carbon composite material.   The non-aqueous electrolyte battery according to claim 1, wherein the negative electrode active material further contains vapor grown carbon fiber (VGCF).   The non-aqueous electrolyte battery according to claim 5, wherein the VGCF has a hollow structure therein, a fiber diameter of 2 to 1000 nm, and an aspect ratio of 10 to 15000.

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