JP2007335405A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery capable of reducing the deterioration of a rate characteristic when stored, in particular, when stored under a high voltage and a high temperature. <P>SOLUTION: This nonaqueous electrolyte secondary battery of the present invention is provided with a positive electrode containing a nickel containing lithium compound oxide as a positive active material, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The separator includes at least one selected out of the group comprising a layer containing a polymer of a monomer containing a halogen atom but not containing hydrogen atom and a layer containing an inorganic oxide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery with improved storage characteristics.

In recent years, in the field of non-aqueous electrolyte secondary batteries, research on lithium ion secondary batteries having high voltage and high energy density has been actively conducted. For example, a cobalt-containing lithium composite oxide (for example, LiCoO ₂ ) exhibiting a high charge / discharge voltage is used as the positive electrode active material in most of the commercially available lithium ion secondary batteries. However, there is a strong demand for higher capacity of the battery, and research and development has been actively conducted on a positive electrode active material having a higher capacity in place of LiCoO ₂ . In particular, research on nickel-containing lithium composite oxide (for example, LiNiO ₂ ) whose main component is nickel has been vigorously conducted. At present, batteries including a predetermined nickel-containing lithium composite oxide have already been commercialized.

On the other hand, for lithium ion secondary batteries, in addition to increasing capacity, higher reliability and longer life are also desired. However, since LiNiO ₂ is generally inferior to LiCoO ₂ in cycle characteristics and thermal safety, a battery containing LiNiO ₂ as a positive electrode active material has not yet occupied the market. Therefore, active material itself is being actively improved in order to improve the characteristics of LiNiO ₂ .

For example, as the positive electrode active material, Li _{a Mb} Ni _c Co _d O _e (M is at least one selected from the group consisting of Al, Mn, Sn, In, Fe, V, Cu, Mg, Ti, Zn, and Mo) And 0 <a <1.3, 0.02 ≦ b ≦ 0.5, 0.02 ≦ d / c + d ≦ 0.9, 1.8 <e <2.2, b + c + d = 1 It is proposed to use (see Patent Document 1). This nickel-containing lithium composite oxide has a small crystal structure accompanying charge / discharge, a high capacity, and good thermal stability.

Furthermore, in order to improve battery characteristics, attempts have been made to improve the separator.
In Patent Document 2, in order to improve the safety of a battery at the time of short circuit or abnormal use, a separator in which a porous fluororesin film made of polytetrafluoroethylene or the like and a polyethylene film or a polypropylene film are stacked is used. Proposed. In Patent Document 2, since the separator includes a fluororesin film having a high melting point, melting of the separator during abnormal heat generation can be prevented. For this reason, the safety | security of a battery can be improved.

  Patent Document 3 proposes to use a separator having two layers having different pore diameters in order to improve the safety of a battery using metallic lithium as a negative electrode active material. The layer having the smaller pore diameter can suppress dendritic growth of metallic lithium, thereby suppressing an internal short circuit during charging and discharging and accompanying ignition. Patent Document 3 discloses a separator in which a polytetrafluoroethylene film and a film made of polypropylene and having a small pore diameter are laminated.

Patent Document 4 proposes using a nonwoven fabric holding polyvinylidene fluoride as a separator. By using the nonwoven fabric held by polyvinylidene fluoride as a separator, the deposition of metallic lithium during overcharge becomes uniform, and the safety during overcharge can be improved.
Japanese Patent Laid-Open No. 5-242891 Japanese Patent Laid-Open No. 5-205721 JP-A-5-258741 JP 2002-042867 A

  Lithium composite oxides such as nickel-containing lithium composite oxides and cobalt-containing lithium composite oxides are known to cause violent elution of their constituent metals, particularly when stored at high voltages and high temperatures. . For example, even when only the technique disclosed in Patent Document 1 is used, metal cations eluted from the positive electrode active material are deposited on the negative electrode, and the impedance of the negative electrode is increased or the separator is clogged. For this reason, such batteries have a reduced rate characteristic after storage.

Even if the separator composed of a polyethylene film or a polypropylene film proposed in Patent Documents 2 and 3 and a polytetrafluoroethylene film is used, if the positive electrode active material is LiCoO ₂ , the elution of metal cations from the positive electrode active material In addition, it is difficult to suppress precipitation of the eluted metal cations on the negative electrode. Moreover, even when the separator made of a nonwoven fabric holding polyvinylidene fluoride proposed in Patent Document 4 is used, when a nickel-containing lithium composite oxide is used as a positive electrode active material, elution of metal cations from the positive electrode active material and It is difficult to suppress precipitation of the eluted metal cations on the negative electrode. For this reason, in the same manner as described above, the battery as described above also has reduced rate characteristics after storage.

  Accordingly, the present invention provides a non-aqueous electrolyte secondary battery that can reduce a decrease in rate characteristics during storage, particularly when stored at high voltage and high temperature, particularly when nickel-containing lithium composite oxide is used as a positive electrode active material. The purpose is to provide.

  The present invention includes a positive electrode including a nickel-containing lithium composite oxide as a positive electrode active material, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The separator includes a halogen atom but a hydrogen atom. The present invention relates to a non-aqueous electrolyte secondary battery including at least one selected from a layer including a monomer polymer not containing hydrogen and a layer including an inorganic oxide.

The nickel-containing lithium composite oxide has the following formula:
LiNi _x M _1-xy Q _y O ₂
(M is at least one of Co and Mn, and Q is Al, Sr, Y, Zr, Ta, Mg, Ti, Zn, B, Ca, Cr, Si, Ga, Sn, P, V, Sb. , Nb, Mo, W, and Fe, and is preferably at least one selected from the group consisting of 0.1 ≦ x ≦ 1, 0 ≦ y ≦ 0.1). In the nickel-containing lithium composite oxide, Q is more preferably at least one selected from the group consisting of Al, Sr, Y, Zr and Ta.

  The polymer is preferably polytetrafluoroethylene.

  The layer containing the inorganic oxide preferably contains at least one selected from the group consisting of a polymer containing an acrylonitrile unit, polyvinylidene fluoride, and polyethersulfone.

  It is preferable that a reduction-resistant film is provided between the separator and the negative electrode. The reduction-resistant film preferably contains a polyolefin. More preferably, the polyolefin is polyethylene or polypropylene.

  Moreover, this invention comprises the said nonaqueous electrolyte secondary battery and the charger which charges a nonaqueous electrolyte secondary battery, and the charge end voltage in a charger is set to 4.3-4.6V. About the system.

  In the nonaqueous electrolyte secondary battery of the present invention, the positive electrode active material includes a nickel-containing lithium composite oxide, and the separator includes a layer including a monomer polymer including a halogen atom but not a hydrogen atom, and an inorganic oxide. Including at least one selected from the group consisting of layers containing objects. For this reason, a portion having a high electron density (NiO oxygen atom) on the surface of the positive electrode active material and a portion having a high electron density in the separator (halogen atom and / or oxygen atom in the inorganic oxide) face each other. A metal cation having a low electron density can be trapped in a region surrounded by oxygen atoms of the above and halogen atoms and / or oxygen atoms in the inorganic oxide. Thereby, even when the nonaqueous electrolyte secondary battery of the present invention is stored at a high voltage and high temperature, metal cations other than lithium ions eluted from the positive electrode active material are trapped between the positive electrode and the separator, It can suppress that a metal cation precipitates on a negative electrode. Therefore, it becomes possible to reduce the deterioration of the rate characteristics of the battery during storage, particularly when stored at high voltage and high temperature.

The best mode for carrying out the present invention will be described in detail below.
The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode including a nickel-containing lithium composite oxide as a positive electrode active material, a negative electrode, a separator interposed therebetween, and a non-aqueous electrolyte. The separator includes at least one selected from the group consisting of a layer containing a monomer polymer and a layer containing an inorganic oxide. The monomer contains a halogen atom but no hydrogen atom.

  As a result of investigating the cause of the above problem and further studying, the present inventors have found the following. That is, the separator containing at least one selected from the group consisting of a layer containing a monomer polymer containing no halogen atom and containing a halogen atom in the molecule and a layer containing an inorganic oxide is a positive electrode active material. It works particularly effectively on certain nickel-containing lithium composite oxides. That is, even when the battery containing the positive electrode active material is stored at a high voltage and high temperature, it is possible to remarkably suppress the precipitation of metal cations other than lithium ions eluted from the positive electrode active material.

The reason is considered as follows. By dissolving Ni in the crystal structure of the positive electrode active material, a metal oxide NiO is generated on the surface of the positive electrode active material. Since NiO is a basic oxide, the electron density on the oxygen atom of NiO is high. Since the halogen atom contained in the separator and the oxygen atom in the inorganic oxide have a high electron withdrawing property, the electron density of the oxygen atom in the halogen atom and the inorganic oxide is high.
When the separator is disposed so as to be adjacent to the positive electrode, a portion having a high electron density (NiO oxygen atom) on the surface of the positive electrode active material and a portion having a high electron density in the separator (halogen atom and / or inorganic oxide) Oxygen atoms). A metal cation having a low electron density can be trapped in a region surrounded by oxygen atoms of NiO and halogen atoms and / or oxygen atoms in the inorganic oxide. As a result, even when stored at a high voltage and a high temperature, metal cations other than lithium ions eluted from the positive electrode active material are trapped between the positive electrode and the separator, and the metal cations are deposited on the negative electrode. Can be suppressed. Therefore, it is possible to reduce a decrease in rate characteristics during storage, particularly when stored at high voltage and high temperature.

  Patent Document 1 proposes to use a nickel-containing lithium composite oxide as a positive electrode active material. However, when a separator made of polypropylene or polyethylene is used, metal cations eluted from the positive electrode active material cannot be trapped. For this reason, the rate characteristics of the battery after storage are lowered.

In Patent Documents 2 and 3, a separator made of polytetrafluoroethylene (PTFE) is used. However, even when a separator made of PTFE is used, when the positive electrode active material is LiCoO ₂ , the metal cations eluted from the positive electrode active material cannot be trapped. Therefore, in such a battery, the rate characteristics after storage deteriorates.

In Patent Document 4, a non-woven fabric holding polyvinylidene fluoride is used as a separator, and LiNiO ₂ is used as a positive electrode active material. However, polyvinylidene fluoride has few parts with high electron density. For this reason, the effect which traps the metal cation eluted from the positive electrode active material between a positive electrode and a separator is weak. Therefore, also in this case, the rate characteristics of the battery after storage are deteriorated.

In the present invention, the separator is at least one selected from the group consisting of a layer containing a monomer polymer containing a halogen atom and no hydrogen atom, and a layer containing an inorganic oxide.
Examples of the layer containing a polymer of a monomer containing a halogen atom and no hydrogen atom include a film containing the polymer. As said polymer, the polymer comprised from a perfluoroalkylene unit, the polymer comprised from a perchloroalkylene unit, etc. are mentioned, for example. For example, when the polymer is composed of perfluoroalkylene units, the perfluoroalkylene units contained may be one type or two or more types. This is the same even when the polymer is composed of other monomer units (for example, perchloroalkylene units).

  In addition to the above, the polymer may be a monomer in which a part of hydrogen atoms are substituted with fluorine atoms and the remaining hydrogen atoms are substituted with chlorine atoms (for example, hydrogen atoms are fluorine atoms and chlorine atoms). Polymers of olefin units substituted with atoms), polymers composed of perfluoroalkyl units and perchloroalkyl units, and the like can be used.

  Examples of the polymer include polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and the like.

  Among the above polymers, a fluoropolymer such as polytetrafluoroethylene (PTFE) is preferable. Polytetrafluoroethylene contains four fluorine atoms having a high electron-withdrawing property in the repeating unit. Further, since the steric hindrance of the polymer molecule is small, the electron density of the fluorine atom contained in PTFE is uniform and high in any part of the polymer. For this reason, the metal cation eluted from the positive electrode active material can be efficiently trapped.

Examples of the layer containing an inorganic oxide include an insulating layer containing an inorganic oxide and a polymer material. The polymer material contained in the insulating layer is not particularly limited, and examples thereof include a polymer containing an acrylonitrile unit, polyvinylidene fluoride, and polyethersulfone.
Of these, polymers containing acrylonitrile units are preferred. In the polymer containing acrylonitrile units, the amount of acrylonitrile units is preferably 20 mol% or more. Examples of the polymer containing an acrylonitrile unit include polyacrylonitrile, polyacrylonitrile-modified rubber, acrylonitrile-styrene-acrylate copolymer, and the like. By using a polymer containing an acrylonitrile unit as the polymer material, the dispersibility of the inorganic oxide and the polymer material in the insulating layer can be improved. For this reason, the said insulating layer comes to be able to trap a metal cation efficiently.

  When a layer containing an inorganic oxide is used as the separator, the layer containing an inorganic oxide may be provided on the entire surface of the negative electrode facing the positive electrode or on the entire surface of the positive electrode facing the negative electrode.

  In the insulating layer, the amount of inorganic oxide is preferably 80 to 99% by weight. When the amount of the inorganic oxide is less than 80% by weight, voids inside the layer are reduced, and lithium ion conductivity is lowered. When the amount of the inorganic oxide is more than 99% by weight, the strength of the insulating layer itself is lowered.

  Examples of inorganic oxides include alumina, titania, zirconia, magnesia, and silica.

  The thickness of the separator is preferably 0.5 to 300 μm. This is the same whether the separator is composed of a layer containing the monomer polymer or a layer containing the inorganic oxide. When a separator contains both the layer containing the said polymer and the layer containing the said inorganic oxide, it is preferable that the total thickness of these two layers is 0.5-300 micrometers.

  The separator is preferably disposed so as not to be in direct contact with the negative electrode. For example, when the separator contains a halogen atom having a high electron-withdrawing property, the carbon atom portion forming the polymer skeleton is in a slightly low electron density due to the strong electron-withdrawing property of the halogen atom. For this reason, when the negative electrode potential is greatly reduced, the carbon atom portion may be easily reduced.

In order to prevent such reduction of the carbon atom portion, for example, a reduction-resistant film is preferably disposed between the negative electrode and the separator. Thereby, it is possible to further reduce the deterioration of the rate characteristics when stored.
For example, a polyolefin film can be used as the reduction-resistant film. Examples of the polyolefin film include a polyethylene film and a polypropylene film.
Further, even when the separator is composed only of the layer containing the inorganic oxide, a reduction-resistant film is provided between the separator and the negative electrode to further suppress deterioration in the rate characteristics of the battery after storage. be able to.

Note that the layer containing the inorganic oxide can function in the same manner as the reducing film, although the degree thereof is somewhat inferior. Therefore, when the separator includes both the layer including the polymer and the layer including the inorganic oxide, the layer including the inorganic oxide is disposed between the layer including the polymer and the negative electrode. Thereby, the reduction | restoration of the layer containing the said polymer can be suppressed.
In this case, the layer containing the inorganic oxide may be formed on the surface of the layer (film) containing the polymer facing the negative electrode, or formed on the surface of the negative electrode facing the layer (film) containing the polymer. You can do it.

  The thickness of the reduction-resistant film is preferably 0.5 to 25 μm. When the thickness of the reduction-resistant film and the reduction-resistant layer is less than 0.5 μm, the positive electrode, the negative electrode, the separator, and the reduction-resistant film or the reduction-resistant layer are wound. Due to the pressure, the reduction-resistant film or the reduction-resistant layer may be crushed, the separator and the negative electrode may come into contact with each other, and the effect of suppressing the reduction of the separator may be insufficient. If the thickness of the reduction-resistant film and the reduction-resistant layer is greater than 25 μm, the direct current resistance is too large and the output characteristics may be degraded.

Below, an example of the manufacturing method of a separator is shown.
A monomer polymer containing a halogen atom but no hydrogen atom is mixed with an organic solvent, and the polymer is melted and kneaded, extruded, then stretched, removed of the organic solvent, dried, and heat set. By applying, a separator can be obtained.
For example, a separator can be obtained by the following method.
First, a polymer and a good solvent for the polymer are mixed to prepare a polymer solution.
The polymer solution as a raw material can be prepared, for example, by dissolving the polymer in a predetermined solvent by heating. The solvent is not particularly limited as long as it can sufficiently dissolve the polymer. Examples thereof include aliphatic or cyclic hydrocarbons such as nonane, decane, undecane, dodecane, and liquid paraffin, or mineral oil fractions having boiling points similar to those of these hydrocarbons. In order to improve the stability of the gel-like molded product obtained after extrusion molding, it is preferable to use a non-volatile solvent such as liquid paraffin.

  The dissolution by heating may be performed with stirring at a temperature at which the polymer is completely dissolved in the solvent, or may be performed while uniformly mixing in the extruder. When the polymer is dissolved in the solvent with stirring, the heating temperature is usually in the range of 140 to 250 ° C., although it varies depending on the type of polymer and solvent used.

When melt | dissolving in an extruder, a polymer is first supplied to an extruder and it fuse | melts. Although a melting temperature changes with kinds of polymer to be used, melting | fusing point + 30-100 degreeC of a polymer is preferable.
Next, a predetermined solvent is supplied to the molten polymer. In this way, a heated solution of the molten polymer can be obtained.

  Next, this solution is extruded into a sheet form from a die of an extruder, and then cooled to obtain a gel composition. At this time, when the polymer solution is prepared in an extruder, the solution may be extruded from the extruder through a die or the like, or the solution is moved to another extruder, and the die or the like. You may extrude through.

  Subsequently, a gel-like molded product is formed by cooling. Cooling is performed by cooling the die or by cooling the gel-like sheet. Cooling is preferably performed at a rate of at least 50 ° C./min to 90 ° C. or less, and more preferably 80 to 30 ° C. As a method for cooling the gel-like sheet, a method of directly contacting a cooling medium such as cold air or cooling water, a method of contacting a roll cooled by the cooling medium, or the like can be used. Among these, a method using a cooling roll is preferable.

  Next, this gel-like molded product is biaxially stretched to obtain a molded product. Stretching is performed at a predetermined magnification by heating the gel-like molded product and using a normal tenter method, roll method, rolling, or a combination of these methods. Biaxial stretching may be either longitudinal or transverse simultaneous stretching or sequential stretching, but simultaneous biaxial stretching is particularly preferable.

The molded product obtained above is washed with a cleaning agent to remove the remaining solvent. Cleaning agents include easily volatile solvents such as hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorinated hydrocarbons such as ethane trifluoride, diethyl ether, Ethers such as dioxane can be used. These may be used alone or in combination of two or more. These cleaning agents are appropriately selected according to the solvent used for dissolving the polymer.
Examples of the method of cleaning the molded product include a method of immersing the molded product in a predetermined cleaning agent to extract a residual solvent, a method of showering the cleaning product on the molded product, or a method using a combination thereof.
The molded product is preferably washed until the residual solvent in the molded product is less than 1% by weight.

  Thereafter, the molded product is dried to remove the cleaning agent. The drying can be performed using a method such as heat drying or air drying.

  Finally, a separator which is a high-strength microporous film can be obtained by performing heat setting on the molded product after drying at a temperature of 100 ° C. or higher.

  The positive electrode includes, for example, a positive electrode current collector and a positive electrode active material layer supported thereon. The positive electrode active material layer includes a nickel-containing lithium composite oxide that is a positive electrode active material, and, if necessary, a binder, a conductive agent, and the like.

As the positive electrode active material, the following formula:
LiNi _x M _1-xy Q _y O ₂
(Wherein M is at least one of Co and Mn, Q is Al, Sr, Y, Zr, Ta, Mg, Ti, Zn, B, Ca, Cr, Si, Ga, Sn, P, Nickel-containing lithium composite oxidation which is at least one selected from the group consisting of V, Sb, Nb, Mo, W, and Fe, and is represented by 0.1 ≦ x ≦ 1, 0 ≦ y ≦ 0.1) It is preferable to use a product. Such a compound has a stable crystal structure, and therefore can provide excellent battery characteristics. The molar ratio x of nickel is more preferably in the range of 0.3 ≦ x ≦ 0.9, and most preferably in the range of 0.7 ≦ x ≦ 0.9. In the above compound, the molar ratio of lithium is increased or decreased by charging and discharging.

  If the molar ratio y of the element Q exceeds 0.1 even if the element Q is any of the above elements, the function of the metal oxide NiO as an electron donor is excessively activated. For this reason, the difference in electron density between the portion having a high electron density on the surface of the positive electrode active material and the portion having a high electron density in the separator is significantly increased. Therefore, the effect of trapping metal cations eluted from the positive electrode active material is weakened. Therefore, the molar ratio y is preferably 0.1 or less.

The element Q is preferably at least one selected from the group consisting of Al, Sr, Y, Zr, and Ta among the above elements. Metal oxides generated from these elements, such as Al ₂ O ₃ and SrO, have the effect of appropriately increasing the function of the metal oxide NiO as an electron donor. When the positive electrode active material contains an oxide of the above element, the electron density of the portion where the electron density on the surface of the positive electrode active material is high is almost equal to the electron density of the halogen atom in the separator or the oxygen atom in the inorganic oxide. . For this reason, it is considered that the effect of trapping metal cations eluted from the positive electrode active material is further improved, and better storage characteristics can be obtained.

  The negative electrode includes, for example, a negative electrode current collector and a negative electrode active material layer carried thereon. The negative electrode active material layer includes a negative electrode active material and, if necessary, a binder, a conductive agent, and the like. Examples of the negative electrode active material include graphite such as natural graphite (flaky graphite), artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, carbon fiber Metal fibers, alloys, lithium metals, tin compounds, silicides, nitrides, and the like can be used.

  Examples of the binder used for the positive electrode and the negative electrode include polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and the like. Used. Here, the binder added to the positive electrode is preferably made of a material containing fluorine atoms, and the binder added to the negative electrode is preferably made of a material not containing fluorine atoms.

  Examples of the conductive agent included in the electrode include graphites, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and other carbon blacks, carbon fibers, and metal fibers.

  For the positive electrode current collector, for example, a sheet made of stainless steel, aluminum, titanium, or the like is used. For the negative electrode current collector, for example, a sheet made of stainless steel, nickel, copper, or the like is used. These thicknesses are not particularly limited, but are preferably 1 to 500 μm.

  The nonaqueous electrolyte includes a nonaqueous solvent and a solute dissolved in the nonaqueous solvent. As the non-aqueous solvent, for example, a cyclic carbonate, a chain carbonate, a cyclic carboxylic acid ester, or the like can be used. Here, examples of the cyclic carbonate include propylene carbonate and ethylene carbonate, and examples of the chain carbonate include diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate. Examples of the cyclic carboxylic acid ester include γ-butyrolactone and γ-valerolactone. These nonaqueous solvents may be used alone or in combination of two or more.

Examples of the solute dissolved in the non-aqueous solvent include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiAsF _6. , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, LiCl, LiBr, LiI, chloroborane lithium such as Li ₂ B ₁₀ Cl ₁₀ , bis (1,2-benzenediolate (2-)-O, O ′ ) Lithium borate, bis (2,3-naphthalenedioleate (2-)-O, O ') lithium borate, bis (2,2'-biphenyldiolate (2-)-O, O') lithium borate, bis (5-Fluoro-2-olate-1-benzenesulfonic acid-O, O ′) borate salts such as lithium borate, lithium bistetrafluoromethanesulfonate imido _{(CF 3 SO 2) 2 NLi} ), tetrafluoromethane acid nonafluorobutanesulfonic acid imide lithium _{(LiN (CF 3 SO 2)} (C 4 F 9 SO 2)), bispentafluoroethanesulfonyl imide lithium (( Imide salts such as C ₂ F ₅ SO ₂ ) ₂ NLi) can be used. These may be used alone or in combination of two or more.

  The nonaqueous electrolyte preferably contains a cyclic carbonate having at least one carbon-carbon unsaturated bond. Such carbonate ester decomposes on the negative electrode to form a film having high lithium ion conductivity. Thereby, the charging / discharging efficiency of a battery can be improved. The amount of the cyclic carbonate having at least one carbon-carbon unsaturated bond is preferably 10% by volume or less of the non-aqueous solvent.

  Examples of the cyclic carbonate having at least one carbon-carbon unsaturated bond include vinylene carbonate, 4-methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4-ethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, Examples include 4-propyl vinylene carbonate, 4,5-dipropyl vinylene carbonate, 4-phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl ethylene carbonate, and divinyl ethylene carbonate. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, and divinyl ethylene carbonate is preferable. In these compounds, some of the hydrogen atoms may be substituted with fluorine atoms.

  Furthermore, the nonaqueous electrolyte may contain a known benzene derivative that decomposes upon overcharge to form a film on the electrode and inactivate the battery. The benzene derivative is preferably a compound having a phenyl group and a cyclic compound group adjacent to the phenyl group. As the cyclic compound group, a phenyl group, a cyclic ether group, a cyclic ester group, a cycloalkyl group, a phenoxy group, and the like are preferable. Specific examples of the benzene derivative include cyclohexylbenzene, biphenyl, diphenyl ether and the like. These may be used alone or in combination of two or more. The content of the benzene derivative is preferably 10% by volume or less of the nonaqueous solvent.

  In the normal operation state, the end-of-charge voltage of the nonaqueous electrolyte secondary battery of the present invention is preferably set to 4.3 to 4.6V. That is, in a system (for example, a mobile phone or a personal computer) that includes the nonaqueous electrolyte battery of the present invention and a charger that charges the battery, the end-of-charge voltage in the charger is set to 4.3 to 4.6V. Preferably it is.

FIG. 2 shows a block diagram of an example of a charger that controls charging of the battery. The charger shown in FIG. 2 also includes a discharge control device.
In this charger, the nonaqueous electrolyte secondary battery 30 of the present invention and the current detector 31 are connected in series. A voltage detector 32 is connected in parallel to a circuit in which the battery 30 and the current detector 31 are connected in series.
Further, the charger includes input terminals 36a and 36b for charging the battery 30, and output terminals 37a and 37b connected to the device. The charger also includes a changeover switch 35 connected in series with the battery 30. The switch 35 is switched to the charge control unit 33 side during charging, and is switched to the discharge control unit 34 side during discharging.

The degree of expansion of the nickel-containing composite oxide that is the positive electrode active material increases as the end-of-charge voltage increases. For this reason, it becomes easy for a nonaqueous electrolyte to enter the inside of an electrode, and the contact property of a positive electrode and a nonaqueous electrolyte improves. Therefore, a local voltage rise at the electrode is suppressed and the voltage is leveled.
When the end-of-charge voltage is lower than 4.3 V, the positive electrode active material is not expanded so much that the non-aqueous electrolyte does not enter the electrode so much that the charging reaction proceeds more on the electrode surface, causing a local voltage increase. Arise. For this reason, the nonaqueous solvent is oxidatively decomposed, and the transition metal element contained in the positive electrode active material is reduced. As a result, a large amount of the transition metal element reduced from the positive electrode active material may be eluted as a metal cation. When the end-of-charge voltage is higher than 4.6 V, the local voltage rise is suppressed, but the voltage is too high, so that oxidative decomposition of the nonaqueous solvent occurs and the transition metal element contained in the positive electrode active material is reduced. May be. Therefore, even in this case, a large amount of metal cations may be eluted from the positive electrode active material.

Example 1
(Battery 1)
(I) Preparation of non-aqueous electrolyte LiPF ₆ was dissolved at a concentration of 1.0 mol / L in a mixed solvent (volume ratio 1: 4) of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) to prepare non-aqueous electrolyte. An electrolyte was obtained.

(Ii) Separator A separator made of polytetrafluoroethylene (PTFE) (BSP0105565-3 manufactured by Gore-Tex Corporation) was used. The separator made of PTFE had a thickness of 54 μm and a porosity of 61%.

(Iii) Production of positive electrode plate Mixing 85 parts by weight of LiNi _0.8 Co _0.2 O ₂ powder as a positive electrode active material, 10 parts by weight of acetylene black as a conductive agent, and 5 parts by weight of polyvinylidene fluoride resin as a binder. did. The obtained mixture was dispersed in an appropriate amount of dehydrated N-methyl-2-pyrrolidone to prepare a slurry-like positive electrode mixture. This positive electrode mixture was applied to both sides of a positive electrode current collector (thickness: 15 μm) made of aluminum foil, dried and rolled to obtain a positive electrode plate (thickness: 160 μm).

(Iv) Production of Negative Electrode Plate 100 parts by weight of artificial graphite powder, 1 part by weight of a polyethylene resin as a binder, and 1 part by weight of carboxymethyl cellulose as a thickener were mixed. An appropriate amount of water was added to the obtained mixture and kneaded to prepare a slurry-like negative electrode mixture. This negative electrode mixture was applied to both sides of a negative electrode current collector (thickness: 10 μm) made of copper foil, dried and rolled to obtain a negative electrode plate (thickness: 160 μm).

(V) Production of Cylindrical Battery A cylindrical battery as shown in FIG. 1 was assembled.
The positive electrode plate 11, the negative electrode plate 12, and the separator 13 disposed between the positive electrode plate 11 and the negative electrode plate 12 were wound in a spiral shape to prepare an electrode plate group. The electrode plate group was housed in a nickel-plated iron battery case 18. One end of the positive electrode lead 14 made of aluminum was connected to the positive electrode plate 11, and the other end of the positive electrode lead 14 was connected to the back surface of the sealing plate 19 that was conducted to the positive electrode terminal 20. One end of the nickel negative electrode lead 15 was connected to the negative electrode plate 12, and the other end of the negative electrode lead 15 was connected to the bottom of the battery case 18. An upper insulating plate 16 is provided above the electrode plate group, and a lower insulating plate 17 is provided below the electrode plate group. A predetermined amount of nonaqueous electrolyte (not shown) prepared as described above was poured into the battery case 18. The opening end of the battery case 18 was caulked to the sealing plate 19 via the gasket 21 to seal the opening of the battery case 18 to complete the battery 1. The design capacity of the battery 1 was 1500 mAh. In the following examples, the design capacity of the battery was 1500 mAh.

(Battery 2)
A battery 2 was produced in the same manner as the battery 1 except that an insulating layer (PAN-containing insulating layer) composed of a polymer (PAN) containing acrylonitrile units and alumina was used as a separator.

The production of the PAN-containing insulating layer was performed according to the following procedure.
970 g of alumina with a median diameter of 0.3 μm was combined with 375 g of polyacrylonitrile modified rubber binder (BM-720H (solid content concentration 8 wt%) from Nippon Zeon Co., Ltd.) and a suitable amount of N-methyl-2-pyrrolidone. The paste was prepared by stirring with a kneader. This paste was applied on both negative electrode active material layers to a thickness of 20 μm, dried, and then further dried at 120 ° C. for 10 hours under vacuum under reduced pressure. Thus, a PAN-containing insulating layer was formed.

<< Comparative Example 1 >>
Comparative battery 1 was produced in the same manner as battery 1 except that a separator made of polyethylene (PE) was used.

<< Comparative Example 2 >>
A comparative battery 2 was produced in the same manner as the battery 1 except that a separator made of polyvinylidene fluoride (PVDF) was used.

<< Comparative Example 3 >>
A comparative battery 3 was produced in the same manner as the battery 1 except that lithium cobaltate (LiCoO ₂ ) was used as the positive electrode active material.

<< Comparative Example 4 >>
A comparative battery 4 was produced in the same manner as the battery 2 except that lithium cobaltate (LiCoO ₂ ) was used as the positive electrode active material.

<< Comparative Example 5 >>
A comparative battery 5 was produced in the same manner as the battery 1 except that LiCoO ₂ was used as the positive electrode active material and a separator made of PE was used.

The separator made of PE and the separator made of PVDF were produced as described above.
Various polymers were dissolved in a predetermined organic solvent to prepare polymer solutions. This solution was extruded into a sheet form from a die of an extruder. Next, the extruded sheet was cooled at a cooling rate of 50 ° C./min to 90 ° C. or less to obtain a gel composition.
Next, the gel-like molded product was biaxially stretched at a predetermined magnification to obtain a molded product. The resulting molded product was then washed with a cleaning agent until the residual solvent was less than 1% by weight of the molded product. The cleaning agent was appropriately changed depending on the type of solvent used.
Thereafter, the molded product was dried to remove the cleaning agent.
Finally, the molded product after drying was heat set at a temperature of 100 ° C. or higher to obtain a separator. These separators had a thickness of 54 μm and a porosity of 61%.

[Evaluation]
(A) Measurement of amount of metal deposited on negative electrode after storage The batteries 1 and 2 and the comparative batteries 1 to 5 manufactured as described above were charged at a constant voltage of 4.3V. The battery after the charge was stored at 85 ° C. for 72 hours.
Thereafter, the battery after storage was disassembled, the central part of the negative electrode plate was cut into a size of 2 cm × 2 cm, and the obtained fragment was washed with ethyl methyl carbonate three times.

  Next, acid was added to the piece and heated to dissolve the piece. After insoluble matter was filtered off, the volume was measured to prepare a measurement sample. This measurement sample was eluted from the positive electrode using an ICP emission spectrophotometer (VARIAN-made VISTA-RL), and the amount of metal deposited on the negative electrode was quantified. In the batteries 1 and 2 and the comparative batteries 1 and 2, the amounts of Ni and Co were quantified, and the total amount was defined as the amount of metal deposited on the negative electrode. In comparative batteries 3 to 5, the amount of Co was quantified, and the amount of Co was defined as the amount of metal deposited on the negative electrode. The results are shown in Table 1. In Table 1, the amount of deposited metal (metal deposition amount) is converted to an amount per unit weight of the negative electrode.

(B) Capacity recovery rate First, each battery was charged at 20 ° C. with a constant current of 1050 mA until the battery voltage reached 4.3 V, and then charged with a constant voltage of 4.3 V for 2 hours 30 minutes. The battery was subjected to constant current / constant voltage charging. Next, the battery after charging was discharged at a discharge current value of 1500 mA (1C) until the battery voltage dropped to 3.0 V, and the discharge capacity before storage was determined.

Next, the discharged battery was charged as described above. The battery after charging was stored at 85 ° C. for 72 hours.
The battery after storage was discharged at a current value of 1 C at 20 ° C., and then further discharged at a current value of 0.2 C. Next, the discharged battery was charged at a constant current of 1050 mA until the battery voltage reached 4.3 V as described above, and then charged at a constant voltage of 4.3 V for 2 hours 30 minutes. Thereafter, the charged battery was discharged at a current value of 1 C until the battery voltage dropped to 3.0V. The discharge capacity at this time was defined as a recovery capacity after storage.
The value obtained as a percentage value of the recovery capacity after storage with respect to the discharge capacity before storage was defined as the capacity recovery rate after storage. The results are shown in Table 1. Table 1 also shows the type of positive electrode active material and separator used.

Using LiNi _0.8 Co _0.2 O ₂ as the positive electrode active material, using a cell 1 and LiNi _0.8 Co _0.2 O ₂ was used a separator made of PTFE as the positive electrode active material, the battery 2 using the PAN-containing insulating layer, after storage The amount of deposited metal decreased and the capacity recovery rate showed a good value. This is because the positive electrode active material surface has a high electron density (NiO oxygen atoms), a PTFE separator with a high electron density (fluorine atoms), or a PAN-containing insulating layer with a high electron density (alumina). This is presumably because the metal cations eluted from the positive electrode were trapped in the region surrounded by the oxygen atoms in the middle.
On the other hand, the amount of metal deposition after storage of Comparative Batteries 1-5 was greater than that of Batteries 1-2. Moreover, the capacity | capacitance recovery rate of the comparative batteries 1-5 was low compared with the batteries 1-2.

Example 2
(Batteries 3 to 50)
Batteries 3 to 50 were produced in the same manner as the battery 1 except that a nickel-containing lithium composite oxide having the composition shown in Table 2 was used as the positive electrode active material.

  For the batteries 3 to 50, the amount of deposited metal and the capacity recovery rate after storage were measured in the same manner as described above. In the measurement of the amount of deposited metal after storage, when the positive electrode active material contained only Ni among Ni, Co, and Mn, the amount of Ni was defined as the amount of deposited metal. When the positive electrode active material contained Ni and Co, the total amount of Ni and Co was defined as the amount of metal deposition. When the positive electrode active material contained Ni and Mn, the total amount of Ni and Mn was defined as the amount of deposited metal. When the positive electrode active material contained Ni, Co, and Mn, the total amount of Ni, Co, and Mn was defined as the amount of metal deposition. The results are shown in Tables 2 and 3. The battery 9 and the battery 1 are the same battery.

From the results of Tables 2 and 3, the formula: LiNi _x M _{1 -xy} Q _y O ₂ (M = at least one of Co and Mn, Q = Al, Sr, Y, Zr, Ta, Mg, Ti, Zn, B , Ca, Cr, Si, Ga, Sn, P, V, Sb, Nb, Mo, W, and Fe, at least one selected from the group consisting of 0.1 ≦ x ≦ 1, 0 ≦ y ≦ 0. It can be seen that a battery having excellent storage characteristics can be obtained by combining the positive electrode active material represented by 1) and a separator made of a monomer polymer containing a halogen atom and no hydrogen atom.

From the results of the batteries 48 to 50, the mixture of the positive electrode active material represented by the above formula, or the positive electrode active material represented by the above formula and other positive electrode active materials (for example, LiCoO ₂ ) not containing Ni. It can be seen that even when the mixture is used, the amount of deposited metal after storage is small, and the capacity recovery rate shows a good value.

From the results of the batteries 3 to 10, the molar ratio x of Ni is preferably 0.1 to 0.9, more preferably 0.3 to 0.9, and 0.7 to 0.9. It can be seen that it is particularly preferred.
Further, in the batteries 3 to 5, particularly the batteries 3 and 4, the molar ratio of Ni contained in the positive electrode active material is small, but compared with the comparative batteries 1 to 5, the amount of deposited metal is small and the capacity recovery rate is a good value. Is shown. From this result, it can be seen that the effect of the present invention can be obtained if the positive electrode active material contains even a small amount of Ni.

  From the results of the batteries 12 to 19 and 36 to 37, when the element Q contained in the positive electrode active material is at least one selected from the group consisting of Al, Sr, Y, Zr and Ta, the storage characteristics are particularly It can be seen that an excellent battery can be obtained.

Example 3
(Batteries 51 to 55)
Batteries 51 to 55 were produced in the same manner as the battery 1 except that a separator made of a material as shown in Table 4 was used.
For the batteries 51 to 55, the amount of deposited metal and the capacity recovery rate after storage were measured in the same manner as described above. In the measurement of the amount of deposited metal after storage, the total amount of Ni and Co was defined as the amount of deposited metal. The results are shown in Table 4. Table 4 also shows the results of batteries 1 and 2.

In Table 4, the symbol of the material which comprises a separator is as follows.
PCTFE: Polychlorotrifluoroethylene PFA: Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer FEP: Tetrafluoroethylene-hexafluoropropylene copolymer PVDF-containing insulating layer: Insulating layer made of polyvinylidene fluoride (PVDF) and alumina PES-containing insulating layer: Insulating layer made of polyethersulfone (PES) and alumina

  Among the above, a separator made of a single polymer was prepared in the same manner as the separator made of PE. These separators had a thickness of 54 μm and a porosity of 61%.

  In the same manner as the PAN-containing insulating layer except that polyvinylidene fluoride (solid content concentration 8% by weight) and polyethersulfone (solid content concentration 8% by weight) were used instead of the polyacrylonitrile-modified rubber binder. A PVDF-containing insulating layer and a PES-containing insulating layer were prepared.

  From Table 4, even when the type of material constituting the separator is changed, the separator is preserved by containing a polymer of a monomer containing a halogen atom and no hydrogen atom, or containing an inorganic oxide. It can be seen that the amount of metal deposited later on the negative electrode decreases and the capacity recovery rate becomes a good value. Similarly to the above, this is a region surrounded by a portion having a high electron density (NiO oxygen atom) on the surface of the positive electrode active material and a portion having a high electron density in the separator (halogen atom or oxygen atom in the inorganic oxide). This is presumably because the metal cations eluted from the positive electrode active material could be trapped.

  Moreover, it can be seen from Table 4 that the battery 1 including the separator made of PTFE has particularly excellent storage characteristics. PTFE contains four fluorine atoms having the highest electron-withdrawing property in the repeating unit, and has few steric hindrances in the polymer molecule. For this reason, the electron density of fluorine atoms in PTFE is uniform and high in any part. Therefore, it is considered that the metal cations eluted from the positive electrode active material can be trapped more efficiently by using the nickel-containing lithium composite oxide as the positive electrode active material and using the separator made of PTFE.

  Among the batteries provided with a layer made of an inorganic oxide and a polymer material, the storage characteristics of the battery 2 in which the layer contains a polymer containing an acrylonitrile unit were particularly excellent. This is presumably because the metal cations were efficiently trapped because of the excellent dispersibility of the polymer and inorganic oxide in the layer.

Example 4
(Batteries 56-59)
In the same manner as in batteries 1 and 2, except that a reduction-resistant film made of polyethylene (PE) (Hypore made by Asahi Kasei Chemicals Co., Ltd., thickness 20 μm) was placed between the separator and the negative electrode. Batteries 56 and 58 were produced.

  Batteries in the same manner as Batteries 1 and 2, except that a reduction-resistant film made of polypropylene (PP) (Celgard 2400, thickness 25 μm) made of polypropylene (PP) was placed between the separator and the negative electrode. 57 and 59 were produced.

  For these batteries, the amount of metal deposited on the negative electrode after storage and the capacity recovery rate after storage were measured in the same manner as described above. In the measurement of the amount of deposited metal after storage, the total amount of Ni and Co was taken as the amount of deposited metal. The results are shown in Table 5. Table 5 also shows the results of batteries 1 and 2.

  As shown in Table 5, batteries 56 and 58 in which a reduction resistant film made of PE is further arranged between the separator and the negative electrode, and a reduction resistant film made of PP is further placed between the separator and the negative electrode. In the batteries 57 and 59 arranged, the amount of metal deposited on the negative electrode after storage was smaller than those of the batteries 1 and 2. Further, the capacity recovery rates of the batteries 56 to 59 were better than the capacity recovery rates of the batteries 1 and 2. This is because a polymer made of PE or PP made of high reduction resistance is arranged on the negative electrode side, so that a separator made of PTFE arranged on the positive electrode side and a polymer containing acrylonitrile units in the PAN-containing insulating layer It is thought that it was possible to prevent the reduction.

Example 5
(Battery 60)
A battery 60 was produced in the same manner as the battery 1 except that a layer containing an inorganic oxide was further provided on the negative electrode. That is, in battery 60, the separator includes a film made of PTFE and a layer containing an inorganic oxide.
For the battery 60, the amount of metal deposited on the negative electrode after storage and the capacity recovery rate after storage were measured in the same manner as described above. In the measurement of the amount of deposited metal after storage, the total amount of Ni and Co was taken as the amount of deposited metal. The results are shown in Table 6. Table 6 also shows the results of battery 1.

The layer containing an inorganic oxide was produced on the negative electrode by the following procedure.
[Method for producing layer containing inorganic oxide]
375 g of N-methyl-2-pyrrolidone (NMP) solution (solid content 8 wt%) containing 970 g of alumina having a median diameter of 0.3 μm and polyacrylonitrile-modified rubber binder (BM-720H manufactured by Nippon Zeon Co., Ltd.) A suitable amount of NMP was stirred with a double-arm kneader to prepare a paste. This paste is applied on both negative electrode active material layers of the negative electrode to a thickness of 5 μm, dried, and further dried at 120 ° C. under vacuum under reduced pressure at 120 ° C. for 10 hours to contain an inorganic oxide. Formed. The thickness of the paste applied on each negative electrode active material layer was 5 μm.

  As shown in Table 6, the battery 60 in which the separator includes both a film made of PTFE and a layer containing an inorganic oxide has a smaller amount of metal deposited on the negative electrode after storage than the battery 1. . In addition, the capacity recovery rate of the battery 60 was better than the capacity recovery rate of the battery 1. This is because the separator further includes a layer containing an inorganic oxide, and the layer containing the inorganic oxide is disposed between the film made of PTFE and the negative electrode, thereby preventing the separator from being reduced. it is conceivable that.

Example 6
In this example, the battery 1 was used, and the amount of metal deposited on the negative electrode after storage (the total amount of Ni and Co) and the capacity recovery rate were measured in the same manner as described above. When performing these measurements, the voltage during charging was set to 4.2V, 4.3V, 4.4V, 4.5V, 4.6V, or 4.7V. The results are shown in Table 7.

  From Table 7, when a nickel-containing lithium composite oxide is used as a positive electrode active material and a separator made of a monomer polymer containing a halogen atom but no hydrogen atom is used, the voltage during charging (that is, charging) It can be seen that by setting the final voltage to 4.3 to 4.6 V, the amount of metal deposited on the negative electrode after storage is significantly reduced, and a good capacity recovery rate can be obtained. This is considered as follows. The degree of expansion of the nickel-containing composite oxide that is the positive electrode active material increases as the end-of-charge voltage increases. For this reason, it becomes easy for a nonaqueous electrolyte to enter the inside of an electrode, and the contact property of a positive electrode and a nonaqueous electrolyte improves. Therefore, the local voltage rise in the electrode is suppressed, and the voltage in the entire electrode is leveled. On the other hand, if the end-of-charge voltage is lower than 4.3 V, the positive electrode active material is not expanded so much that the non-aqueous electrolyte does not enter the electrode so much that the charging reaction proceeds more on the electrode surface. An increase occurs. For this reason, the nonaqueous solvent is oxidized and decomposed, and a large amount of metal cations are eluted from the positive electrode active material. When the end-of-charge voltage is higher than 4.6 V, the local voltage rise is suppressed, but the voltage is too high, so that oxidative decomposition of the non-aqueous solvent occurs. Cations are eluted. When the end-of-charge voltage is lower than 4.3 V or higher than 4.6 V, since the amount of the eluted metal cation is large, only a part of the metal cation is trapped between the positive electrode and the separator, and the rest The metal cation is considered to be deposited on the negative electrode.

  The nonaqueous electrolyte secondary battery of the present invention can suppress the deterioration of rate characteristics even after being stored at a high voltage and high temperature. For this reason, the nonaqueous electrolyte secondary battery of the present invention can be used as a power source for equipment that may be stored at a high temperature, for example.

It is a longitudinal cross-sectional view which shows schematically the cylindrical nonaqueous electrolyte secondary battery produced in the Example. It is a block diagram which shows the structure of the charger incorporating the nonaqueous electrolyte secondary battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Positive electrode plate 12 Negative electrode plate 13 Separator 14 Positive electrode lead 15 Negative electrode lead 16 Upper insulating plate 17 Lower insulating plate 18 Battery case 19 Sealing plate 20 Positive electrode terminal 21 Gasket 30 Nonaqueous electrolyte secondary battery 31 Current detection part 32 Voltage detection part 33 Charging Control part 34 Discharge control part 35 Changeover switch 36a, 36b Input terminal 37a, 37b Output terminal

Claims (9)

Comprising a positive electrode containing a nickel-containing lithium composite oxide as a positive electrode active material, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte;
The separator is a nonaqueous electrolyte secondary battery including at least one selected from the group consisting of a layer containing a monomer polymer containing a halogen atom but no hydrogen atom, and a layer containing an inorganic oxide. The nickel-containing lithium composite oxide has the following formula:
LiNi _x M _1-xy Q _y O ₂
(M is at least one of Co and Mn, and Q is Al, Sr, Y, Zr, Ta, Mg, Ti, Zn, B, Ca, Cr, Si, Ga, Sn, P, V, Sb. And a compound represented by 0.1 ≦ x ≦ 1, 0 ≦ y ≦ 0.1), which is at least one selected from the group consisting of Nb, Mo, W, and Fe. Non-aqueous electrolyte secondary battery.   The nonaqueous electrolyte secondary battery according to claim 2, wherein the element Q is at least one selected from the group consisting of Al, Sr, Y, Zr, and Ta.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the polymer is polytetrafluoroethylene.   The non-aqueous electrolyte 2 according to any one of claims 1 to 3, wherein the layer containing the inorganic oxide contains at least one selected from the group consisting of a polymer containing an acrylonitrile unit, polyvinylidene fluoride, and polyethersulfone. Next battery.   The nonaqueous electrolyte secondary battery according to claim 1, wherein a reduction-resistant film is provided between the separator and the negative electrode.   The nonaqueous electrolyte secondary battery according to claim 6, wherein the reduction-resistant film includes a polyolefin.   The nonaqueous electrolyte secondary battery according to claim 7, wherein the polyolefin is polyethylene or polypropylene.   A non-aqueous electrolyte secondary battery according to any one of claims 1 to 8 and a charger for charging the non-aqueous electrolyte secondary battery, wherein a charge end voltage in the charger is 4.3 to 4. System set to 6V.

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