JP2017182990A - Positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel and improved positive electrode for a nonaqueous electrolyte secondary battery which enables the improvement in cycle life under a high-temperature, high-voltage condition; and a nonaqueous electrolyte secondary battery.SOLUTION: To solve the above problem, a positive electrode for a nonaqueous electrolyte secondary battery is provided according to an aspect of the present invention. The positive electrode comprises: a positive electrode current collector; a coating layer including graphite, and covering the positive electrode current collector; a positive electrode active material having a composition represented by the chemical formula 1 below; and a conductive assistant of which the BET specific surface area is 35-350 m/g. LiNiMnMO(1). In the chemical formula 1, M represents one or more metal elements selected from a particular transition metal and aluminum, and the particular transition metal is a transition metal other than nickel (Ni) and manganese (Mn); and x, y and z are values in the ranges given by 0.02≤x≤1.10, 0.25≤y≤0.6 and 0.0<z≤0.10 respectively.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries are required to have higher energy density. And as a means for raising the energy density of a nonaqueous electrolyte secondary battery, using the positive electrode active material which has the spinel type crystal structure currently disclosed by patent document 1, for example is proposed. When such a positive electrode active material is used as the positive electrode active material of the nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary battery can be charged / discharged at a voltage of 4.5 V or more, for example.

JP 2014-120331 A

  However, the non-aqueous electrolyte secondary battery using such a positive electrode active material has a problem that the cycle life under a high temperature and a high voltage is remarkably reduced. The present inventor considers this reason as follows. That is, when charging / discharging is performed under high temperature and high voltage, metal ions (ion) are eluted from the positive electrode current collector into the electrolyte solution. For example, when aluminum (Al) is used as the current collector, aluminum ions are eluted in the electrolytic solution. And this metal ion precipitates on a negative electrode, and forms a coating layer on a negative electrode. This coating layer increases battery resistance and reduces cycle life. Alternatively, the aluminum deposited on the negative electrode penetrates the separator and reaches the positive electrode to cause a short circuit, resulting in a decrease in cycle life.

As a technique for suppressing elution of metal ions from the current collector, a technique for forming a passive film on the surface of the current collector has been proposed. For example, when aluminum is used as the current collector, the current collector is covered with an alumina (Al ₂ O ₃ ) film or an aluminum fluoride (AlF ₃ ) film. This technique can achieve a certain effect when charging / discharging under a low voltage (for example, 4.3 V). However, when charging / discharging under the above-described high temperature and high voltage is performed, this technique cannot sufficiently suppress elution of metal ions.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved non-aqueous solution capable of improving the cycle life under high temperature and high voltage. It is providing the positive electrode for electrolyte secondary batteries, and a nonaqueous electrolyte secondary battery.

In order to solve the above problems, according to one aspect of the present invention, a positive electrode current collector, a coating layer containing graphite and covering the positive electrode current collector, and a positive electrode active material having a composition represented by the following chemical formula 1 There is provided a positive electrode for a non-aqueous electrolyte secondary battery, comprising a substance and a conductive additive having a BET specific surface area of 35 to 350 m ² / g.
Li _x Ni _y Mn _2-yz M _z O ₄ (1)
In Chemical Formula 1, M is any one or more metal elements selected from a specific transition metal and aluminum, and the specific transition metal is a transition metal excluding nickel (Ni) and manganese (Mn), x, y and z are values in the ranges of 0.02 ≦ x ≦ 1.10, 0.25 ≦ y ≦ 0.6, and 0.0 <z ≦ 0.10.

  According to this aspect, the positive electrode active material represented by Chemical Formula 1 is used. This positive electrode active material has a so-called spinel crystal structure. For this reason, when a nonaqueous electrolyte secondary battery is produced using the positive electrode for a nonaqueous electrolyte secondary battery according to this aspect, the nonaqueous electrolyte secondary battery can be charged and discharged under a high voltage. For example, the upper limit value of the cut-off voltage for charging can be set to 4.5 V or more. In addition, since the positive electrode current collector is covered with a coating layer containing graphite, it suppresses the elution of metal ions from the positive electrode current collector when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage. can do. Therefore, the cycle life of the nonaqueous electrolyte secondary battery is improved.

  Here, in chemical formula 1, M is aluminum (Al), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), Selected from the group consisting of molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), cerium (Ce) One or more metal elements may be used.

  According to this aspect, the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage can be improved.

  In Chemical Formula 1, y may be a value within the range of 0.40 ≦ y <0.60.

  According to this aspect, the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage can be improved.

The conductive auxiliary agent may have a BET specific surface area of 45 to 350 m ² / g.

  According to this aspect, the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage can be improved.

Moreover, 100-300 m < ² > / g may be sufficient as the BET specific surface area of a conductive support agent.

  According to this aspect, the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage can be improved.

Moreover, 120-220 m < ² > / g may be sufficient as the BET specific surface area of a conductive support agent.

  According to this aspect, the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage can be improved.

  In addition, the conductive auxiliary agent may contain carbon black.

  According to this aspect, the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage can be improved.

  According to another aspect of the present invention, there is provided a nonaqueous electrolyte secondary battery comprising the positive electrode for a nonaqueous electrolyte secondary battery.

  According to this aspect, the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage can be improved.

  Here, as a solvent for the electrolytic solution, at least one fluoro-based nonaqueous solvent may be included.

  According to this aspect, the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at high temperature and high voltage can be improved.

  As described above, according to the present invention, it is possible to improve the cycle life when the nonaqueous electrolyte secondary battery is charged and discharged at a high temperature and a high voltage.

It is explanatory drawing which shows schematic structure of the nonaqueous electrolyte secondary battery which concerns on embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<2. Configuration of non-aqueous electrolyte secondary battery>
Below, with reference to FIG. 1, the specific structure of the nonaqueous electrolyte secondary battery 10 which concerns on one Embodiment of this invention mentioned above is demonstrated. FIG. 1 is an explanatory view illustrating the configuration of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

  As shown in FIG. 1, the nonaqueous electrolyte secondary battery 10 includes a positive electrode 20, a negative electrode 30, and a separator layer 40. The form of the nonaqueous electrolyte secondary battery 10 is not particularly limited. For example, the nonaqueous electrolyte secondary battery 10 may be any one of a cylindrical shape, a rectangular shape, a laminate shape, a button shape, and the like.

  The positive electrode 20 includes a positive electrode current collector 21, a coating layer 21 a, and a positive electrode active material layer 22. The positive electrode current collector 21 is made of, for example, aluminum. The covering layer 21 a covers one surface of the positive electrode current collector 21. The covering layer 21 a is disposed at the interface between the positive electrode current collector 21 and the positive electrode active material layer 22. Therefore, for example, when the positive electrode active material layers 22 are disposed on both surfaces of the positive electrode current collector 21 (for example, when the nonaqueous electrolyte secondary battery 10 is a wound secondary battery), the positive electrode current collector 21 It is preferable that the coating layer 21a is disposed on both sides of the film. This is for more reliably suppressing elution of metal ions from the positive electrode current collector 21.

  The coating layer 21a contains graphite. As shown in the examples described later, the cycle life was significantly improved by covering the positive electrode current collector 21 with graphite. Therefore, it is estimated that elution of metal ions from the positive electrode current collector 21 was suppressed by graphite.

  Here, the graphite that can be used in the present embodiment is not particularly limited. Examples of graphite include, for example, flake graphite generated by performing pulverization control so as to peel off layers with weak binding force without breaking natural graphite or artificial graphite as much as possible. . Graphite has an advantage that the specific surface area is small as compared with other conductive materials such as carbon black, and the slurry property can be kept good as a coating material. Therefore, the applicability on the current collector is good and defects are hardly generated.

  The coating layer 21a may contain other components such as a binder as long as the effects of the present embodiment are not impaired. Examples of such a binder include a binder used in the positive electrode active material layer 22.

The thickness of the coating layer 21a is not particularly limited, but may be 0.5 to 2 μm, for example. When the thickness of the coating layer 21a is less than 0.5 μm, the opportunity and area where the conductive additive and the positive electrode current collector 21 are in contact with each other is reduced, so that the resistance value may not be sufficiently reduced. Moreover, since the coating of the coating layer 21a may be incomplete, the role of protecting the positive electrode current collector 21, which is the original purpose, from high charging pressure may be impaired. On the other hand, when the thickness of the coating layer 21a exceeds 2 μm, the resistance value increases in proportion to the thickness, so that the resistance value may not decrease. Further, the surface density of graphite is not particularly limited, but is preferably about 0.05 to 0.3 mg / cm ² .

  The coating layer 21a is formed, for example, by applying a slurry obtained by dispersing the material of the coating layer 21a in ion-exchanged water onto the positive electrode current collector 21 and drying it. From the viewpoint of applying a slurry in which the positive electrode active material layer is dispersed in an organic solvent (because the organic solvent may come into contact with the coating layer once dried), the coating layer is It is desirable to apply a material dispersed in ion exchange water.

The positive electrode active material layer 22 includes at least a positive electrode active material and a conductive additive, and may further include a binder. The positive electrode active material has a composition represented by the following chemical formula 1 and has a spinel crystal structure.
Li _x Ni _y Mn _2-yz M _z O ₄ (1)
In chemical formula 1, M is any one or more metal elements selected from a specific transition metal and aluminum. The specific transition metal is a transition metal excluding nickel and manganese. x, y, and z are values within the ranges of 0.02 ≦ x ≦ 1.10, 0.25 ≦ y ≦ 0.6, and 0.0 <z ≦ 0.10.

  In Chemical Formula 1, M is aluminum (Al), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo ), Tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce). Or it is preferable that they are 2 or more types of metal elements.

  In Chemical Formula 1, y is preferably a value within the range of 0.40 ≦ y <0.60. Z may be 0.

  Since the positive electrode active material represented by Chemical Formula 1 has a spinel crystal structure, the nonaqueous electrolyte secondary battery 10 can be charged and discharged under a high voltage. For example, the upper limit value of the cut-off voltage for charging can be set to 4.5V or more, preferably about 4.9V. However, when the nonaqueous electrolyte secondary battery 10 is charged and discharged at a high temperature and under a high voltage, metal ions may be eluted from the positive electrode current collector 21. Therefore, in this embodiment, elution of metal ions is suppressed by covering the positive electrode current collector 21 with the coating layer 21a. The content of the positive electrode active material is not particularly limited, and may be any content as long as it is a content applied to the positive electrode active material layer of the conventional nonaqueous electrolyte secondary battery.

The BET specific surface area of a conductive support agent is 35-350 m < ² > / g. BET specific surface area is preferably 45~350m ² / g, more preferably 100 to 300 m ² / g, more preferably 120~220m ² / g. As will be shown in Examples described later, when the BET specific surface area of the conductive auxiliary agent is a value within these ranges, the cycle life is further improved. A positive electrode active material having a spinel crystal structure has a low powder resistivity at room temperature (for example, about 10 ⁻⁶ to 10 ⁻⁷ Ωcm). For this reason, it is very important to increase the conductivity of the positive electrode active material layer 22 with the conductive assistant. In the present embodiment, by using a conductive additive having such a BET specific surface area, the conductivity of the positive electrode active material layer 22 can be increased, and hence the cycle life of the nonaqueous electrolyte secondary battery 10 can be improved. . The BET specific surface area can be measured by, for example, a high-accuracy and multi-analyte gas adsorption amount measuring apparatus (Autosorb, Canterchrome Instruments). In addition, content in particular of a conductive support agent is not restrict | limited, Any may be sufficient if it is content applied to the positive electrode active material layer of a nonaqueous electrolyte secondary battery.

  Examples of the conductive aid include carbon black such as ketjen black, acetylene black, and furnace black. Among these, any one or more carbon blacks may be contained. Of these carbon blacks, a preferred example is acetylene black. Acetylene black has fewer defects than other carbon blacks. The defective part of carbon black may react with the electrolytic solution when the nonaqueous electrolyte secondary battery 10 is charged and discharged under a high voltage. When the reaction occurs, gas is generated, and the nonaqueous electrolyte secondary battery 10 may expand. From such a viewpoint, the carbon black is preferably acetylene black.

  Examples of the binder include polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butylene rubber, acrylonitrile butadiene rubber, and acrylonitrile butadiene rubber. ), Fluoroelastomer, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, and the like. The binder is not particularly limited as long as it can bind the positive electrode active material and the conductive additive onto the positive electrode current collector 21. Further, the content of the binder is not particularly limited and may be any content as long as it is applied to the positive electrode active material layer of the non-aqueous electrolyte secondary battery.

  The positive electrode active material layer 22 is, for example, a slurry in which a positive electrode active material, a conductive aid, and a binder are dispersed in a suitable organic solvent (for example, N-methyl-2-pyrrolidone). (Slurry) is coated on the coating layer 21a, dried and rolled.

  The negative electrode 30 includes a negative electrode current collector 31 and a negative electrode active material layer 32. The negative electrode current collector 31 is made of, for example, copper, nickel, or the like.

The negative electrode active material layer 32 may be any material as long as it is used as a negative electrode active material layer of a nonaqueous electrolyte secondary battery. For example, the negative electrode active material layer 32 includes a negative electrode active material, and may further include a binder. Examples of the negative electrode active material include graphite active materials (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, etc.), silicon (Si), tin (Sn), or oxides thereof. A mixture of fine particles of graphite and a graphite active material, fine particles of silicon or tin, alloys based on silicon or tin, and titanium oxide (TiO _x ) compounds such as Li ₄ Ti ₅ O ₁₂ can be used. . Note that the oxide of silicon is represented by SiO _x (0 ≦ x ≦ 2). In addition to these, for example, metallic lithium can be used as the negative electrode active material.

  As the binder, for example, styrene butadiene rubber (SBR) is used. The mass ratio between the negative electrode active material and the binder is not particularly limited, and the mass ratio employed in the conventional non-aqueous electrolyte secondary battery can also be applied in the present invention.

  Separator layer 40 includes a separator and an electrolytic solution.

  The separator according to one embodiment of the present invention is not particularly limited. Any separator body according to an embodiment of the present invention can be used as long as it is used as a separator for a non-aqueous electrolyte secondary battery. For example, as the separator, it is preferable to use a porous film or a non-woven fabric exhibiting excellent high rate discharge performance alone or in combination. Examples of the material constituting the separator include, for example, polyolefin resins represented by polyethylene, polypropylene, and the like, polyethylene terephthalate, and polybutylene terephthalate. Polyester resin, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluorovinylether (perfluorovinylether) Polymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoro Acetone (hexafluoroacetone) copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride- Tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-ethylene-teto It can be used fluoroethylene copolymer. In addition, the porosity of the separator is not particularly limited, and the porosity of the separator of the nonaqueous electrolyte secondary battery can be arbitrarily applied.

Moreover, the separator may have a coating layer containing an inorganic filler. Specifically, the coating layer may contain at least one of Mg (OH) _{2 and} Al ₂ O ₃ as an inorganic filler. According to such a configuration, the coating layer containing the inorganic filler prevents the direct contact between the positive electrode and the separator, thereby preventing the oxidation and decomposition of the electrolytic solution generated on the surface of the positive electrode during high temperature storage, and the decomposition generation of the electrolytic solution. It is possible to suppress the generation of gas that is a product.

  Here, the coating layer containing an inorganic filler may be formed on both surfaces of the separator, or may be formed only on one surface of the separator on the positive electrode side. If the coating layer containing an inorganic filler is formed at least on the positive electrode side, direct contact between the positive electrode and the electrolytic solution can be prevented.

  The present invention is not limited to the above examples. For example, the coating layer containing an inorganic filler may be formed on the positive electrode instead of on the separator. In such a case, the coating layer containing the inorganic filler can be formed on both surfaces of the positive electrode, thereby preventing direct contact between the positive electrode and the separator. Needless to say, the coating layer containing the inorganic filler may be formed on both the positive electrode and the separator.

  The electrolytic solution contains various non-aqueous solvents used for lithium ion secondary batteries. It is particularly preferable that the solvent contains at least one fluoro nonaqueous solvent such as hydrofluoroether (HFE) and fluorocarbonate (fluoroethylene carbonate or the like). The solvent may further contain a chain carbonate ester.

Hydrofluoroethers have improved oxidation resistance by substituting some of the ether hydrogens with fluorine. Examples of such hydrofluoroethers include 2,2,2-trifluoroethyl methyl ether (CF ₃ CH ₂ OCH ₃ ), 2,2,2- Trifluoroethyl difluoromethyl ether (CF ₃ CH ₂ OCHF ₂ ), 2,2,3,3,3-pentafluoropropyl methyl ether (CF ₃ CF ₂ CH ₂ OCH ₃ ), _{2, 2, 3} , ₃ , ₃ - pentafluoropropyl difluoromethyl ether _{(CF 3 CF 2 CH 2 OCHF} 2), 2,2,3,3,3- pentafluoro-propyl-1,1,2,2-tetrafluoroethyl ether _(CF 3 CF 2 CH _{2 OCF 2 CF 2 H),} 1,1,2,2- tetrafluoroethyl methyl ether _(HCF 2 _CF 2 OC _3), 1,1,2,2-tetrafluoroethyl ethyl ether _{(HCF 2 CF 2 OCH 2 CH} 3), 1,1,2,2- tetrafluoroethyl propyl ether _{(HCF 2 CF 2 OC 3 H} 7) 1,1,2,2-tetrafluoroethyl butyl ether (HCF ₂ CF ₂ OC ₄ H ₉ ), 1,1,2,2-tetrafluoroethyl isobutyl ether (HCF ₂ CF ₂ OCH ₂ CH (CH ₃ ) ₂ ), 1,1,2,2-tetrafluoroethyl isopentyl ether (HCF ₂ CF ₂ OCH ₂ C (CH ₃ ) ₃ ), 1,1,2,2-tetrafluoroethyl-2,2,2-tri trifluoroethyl ether _{(HCF 2 CF 2 OCH 2 CF} 3), 1,1,2,2- tetrafluoroethyl-2,2,3,3-tetrafluoro-flop Pill ether _{(HCF 2 CF 2 OCH 2 CF} 2 CF 2 H), hexafluoroisopropyl ether _{((CF 3) 2 CHOCH 3} ), 1,1,3,3,3- pentafluoro-2-trifluoromethyl-propyl Methyl ether ((CF ₃ ) ₂ CHCF ₂ OCH ₃ ), 1,1,2,3,3,3-hexafluoropropyl methyl ether (CF ₃ CHFCF ₂ OCH ₃ ), 1,1,2,3,3 Examples include 3-hexafluoropropyl ethyl ether (CF ₃ CHFCF ₂ OCH ₂ CH ₃ ) and 2,2,3,4,4,4-hexafluorobutyl difluoromethyl ether (CF ₃ CHFCF ₂ CH ₂ OCHF ₂ ). .

Examples of the electrolyte salt include LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO _4. , Inorganic ion salts containing one of lithium (Li), sodium (Na) or potassium (K), such as KSCN, LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NC _{lO 4, (n-C 4} H 9) 4 NI, (C 2 H 5) 4 N-maleate, (C 2 H 5) 4 N-benzoate, (C 2 H 5) 4 N-phtalate, stearyl acid Organic ion salts such as lithium (lithium stearyl sulfate), lithium octyl sulfonate (lithium octyl sulfate), lithium dodecylbenzene sulfonate (lithium dodecylbenzene sulfate), and the like can be used. These ionic compounds can be used alone or in admixture of two or more. Further, the concentration of the electrolyte salt may be the same as that of the nonaqueous electrolytic solution used in the conventional lithium secondary battery, and is not particularly limited. In the present invention, an electrolytic solution containing an appropriate lithium compound (electrolyte salt) at a concentration of about 0.5 to 2.0 mol / L can be used.

<3. Manufacturing method of non-aqueous electrolyte secondary battery>
(3-1. Method for producing positive electrode active material)
First, the manufacturing method of a positive electrode active material is demonstrated. Although the manufacturing method in particular of a positive electrode active material is not restrict | limited, For example, a coprecipitation method can be used. Below, an example is given and demonstrated about the manufacturing method of the positive electrode active material using this coprecipitation method.

First, nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O), manganese sulfate pentahydrate (MnSO ₄ · 5H ₂ O), and a compound containing a metal element M are dissolved in ion-exchanged water to obtain a mixed aqueous solution. Manufacturing. Here, the total mass of the compound containing nickel sulfate hexahydrate, manganese sulfate pentahydrate, and metal element M may be, for example, about 20% by mass with respect to the total mass of the mixed aqueous solution. Further, the nickel sulfate hexahydrate, manganese sulfate pentahydrate, and the compound containing the metal element M are mixed so that the mole ratio of each element of Ni, Mn, and M becomes a desired value. . In addition, although the molar ratio of each element is determined according to the composition of the positive electrode active material to be manufactured, for example, when manufacturing LiNi _0.5 Mn _1.45 Al _0.05 O ₄ , the mole of each element. The ratio Ni: Mn: Al is 50: 145: 5.

  The metal element M includes aluminum (Al), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo ), Tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce). Or it is preferable that they are 2 or more types of metal elements. Examples of the compound containing the metal element M include various salts such as sulfate and nitrate of the metal element M, oxides, hydroxides, and the like.

  In addition, a predetermined amount (for example, 500 ml) of ion exchange water is added to the reaction layer, and the temperature of this ion exchange water is maintained at 50 ° C. Hereinafter, the aqueous solution in the reaction layer is referred to as a reaction layer aqueous solution. Next, dissolved oxygen is removed by bubbling ion exchange water with an inert gas such as nitrogen.

Subsequently, the ion-exchanged water in the reaction layer is stirred, and the above-described mixed aqueous solution is dropped into the ion-exchanged water while maintaining the temperature of the ion-exchanged water at 50 ° C. Further, an excessive amount of saturated aqueous NaCO ₃ solution is dropped into ion-exchanged water with respect to Ni, Mn, and M of the mixed aqueous solution. During dropping, the pH of the aqueous reaction layer solution is maintained at 11.5 and the temperature is maintained at 50 ° C. The dropping speed of the mixed aqueous solution and the saturated NaCO ₃ aqueous solution is not particularly limited, but if it is too fast, a uniform precursor (coprecipitated hydroxide salt) may not be obtained. For example, the dropping speed may be about 3 ml / min. The mixed aqueous solution and the saturated aqueous NaCO ₃ solution are dropped in a predetermined time, for example, about 10 hours. Thereby, the hydroxide salt of each metal element co-precipitates.

  Subsequently, solid-liquid separation (for example, suction filtration) is performed, the coprecipitated hydroxide salt is taken out from the aqueous reaction layer solution, and the taken out coprecipitated hydroxide salt is washed with ion-exchanged water. Further, the coprecipitated hydroxide salt is vacuum dried. The temperature at this time may be about 100 ° C., for example, and the drying time may be about 10 hours, for example.

Next, the dried coprecipitated hydroxide salt is pulverized for several minutes in a mortar to obtain a dry powder. Then, a dry powder, by mixing a lithium carbonate _(Li 2 CO _3), to produce a mixed powder. Here, the molar ratio between Li and Ni + Mn + M (= Me) is determined according to the composition of the positive electrode active material. For example, when producing LiNi _0.5 Mn _1.45 Al _0.05 O ₄ , the molar ratio Li: Me between Li and Me is 1.0: 2.0.

  Further, the mixed powder is fired. In addition, you may perform baking in air | atmosphere. Further, the firing time and firing temperature may be adjusted arbitrarily. The firing temperature may be, for example, about 900 to 1100 ° C., and the firing time may be, for example, about 6 hours. Through the above steps, a positive electrode active material is produced.

(3-2. Manufacturing method of non-aqueous electrolyte secondary battery)
Then, an example of the manufacturing method of the nonaqueous electrolyte secondary battery 10 is demonstrated. In addition, the manufacturing method demonstrated below is an example to the last, and, of course, the nonaqueous electrolyte secondary battery 10 can be manufactured by another method.

  The positive electrode 20 is manufactured as follows. First, the coating layer 21 a is formed on the positive electrode current collector 21. Specifically, the material constituting the coating layer 21a (for example, natural graphite and binder described above) is styrene butadiene rubber (SBR), and CMC is in a desired mass ratio (for example, 1: 1: 1) ( A slurry is formed by dispersing what is weighed in (mass ratio) in ion-exchanged water. Next, the slurry is applied on the positive electrode current collector 21 and dried to form a coating layer 21 a on the positive electrode current collector 21. The coating method is not particularly limited, and for example, a knife coater method, a gravure coater method, or the like may be used. The following coating steps are also performed by the same method.

  Next, a slurry is formed by dispersing materials (for example, a positive electrode active material, a conductive additive, and a binder) constituting the positive electrode active material layer 22 in an organic solvent (for example, N-methyl-2-pyrrolidone). . Next, the positive electrode active material layer 22 is formed by applying the slurry onto the coating layer 21a and drying the slurry. Furthermore, the positive electrode active material layer 22 is compressed to a desired thickness by a compressor. Thereby, the positive electrode 20 is manufactured. Here, the thickness of the positive electrode active material layer 22 is not particularly limited as long as the positive electrode active material layer of the nonaqueous electrolyte secondary battery has a thickness. Note that the step of applying the positive electrode active material to the current collector may be performed in a dry environment.

  First, the negative electrode 30 is prepared by mixing a negative electrode active material, carboxymethyl cellulose (CMC), and a conductive additive at a desired ratio, adding a predetermined amount of ion-exchanged water, and kneading and mixing. Thereafter, ion exchange water is further added to adjust the viscosity, and a styrene butadiene rubber (SBR) binder is added to form a negative electrode slurry. Next, the negative electrode active material layer 32 is formed by applying the slurry onto the negative electrode current collector 31 and drying the slurry. Further, the negative electrode active material layer 32 is compressed to a desired thickness by a compressor. Thereby, the negative electrode 30 is manufactured. Here, the thickness of the negative electrode active material layer 32 is not particularly limited as long as the negative electrode active material layer of the nonaqueous electrolyte secondary battery has a thickness. In addition, when metal lithium is used for the negative electrode active material layer 32, a metal lithium foil may be stacked on the negative electrode current collector 31.

  Subsequently, the electrode structure is manufactured by sandwiching the separator between the positive electrode 20 and the negative electrode 30. Next, the electrode structure is processed into a desired shape (for example, a cylindrical shape, a square shape, a laminate shape, a button shape, etc.) and inserted into a container of the shape. Furthermore, by injecting an electrolytic solution having a desired composition into the container, each pore in the separator is impregnated with the electrolytic solution. Thereby, the nonaqueous electrolyte secondary battery 10 is manufactured.

<1. Example 1>
Below, the Example which concerns on this embodiment is described.
(1-1. Preparation of positive electrode active material)
First, nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and manganese sulfate pentahydrate (MnSO ₄ · 5H ₂ O) were dissolved in ion-exchanged water to produce a mixed aqueous solution. Here, the total mass of nickel sulfate hexahydrate and manganese sulfate pentahydrate was about 20 mass% with respect to the total mass of the mixed aqueous solution. The molar ratio Ni: Mn of each element was 5:15.

  On the other hand, 500 ml of ion exchange water was added to the reaction layer, and the temperature of this ion exchange water was maintained at 50 ° C. Next, dissolved oxygen was removed by bubbling ion-exchanged water with an inert gas (gas) such as nitrogen.

Subsequently, the ion exchange water in the reaction layer was stirred, and the above-mentioned mixed aqueous solution was dropped into the ion exchange water while maintaining the temperature of the ion exchange water at 50 ° C. Furthermore, an excessive amount of saturated aqueous NaCO ₃ solution was dropped into ion-exchanged water with respect to Ni and Mn of the mixed aqueous solution. During the dropwise addition, the pH of the aqueous reaction layer solution was maintained at 11.5 and the temperature was maintained at 50 ° C. The dropping rate of the mixed aqueous solution and the saturated aqueous NaCO ₃ solution was about 3 ml / min. The mixed aqueous solution and saturated aqueous NaCO ₃ solution were added dropwise over 10 hours. Thereby, the hydroxide salt of each metal element coprecipitated.

  Subsequently, solid-liquid separation (for example, suction filtration) was performed, the coprecipitated hydroxide salt was taken out from the aqueous reaction layer solution, and the taken out coprecipitated hydroxide salt was washed with ion-exchanged water. Further, the coprecipitated hydroxide salt was vacuum dried. The drying temperature was about 100 ° C., and the drying time was about 10 hours.

Next, the dried coprecipitated hydroxide salt was pulverized for several minutes in a mortar to obtain a dry powder. Then, a dry powder, by mixing a lithium carbonate _(Li 2 CO _3), to produce a mixed powder. Here, the molar ratio Li: Me between Li and Ni + Mn (= Me) was 1.0: 2.0.

Further, the mixed powder was fired in the air. The firing temperature was maintained at a temperature in the range of 900 to 1100 ° C., and the firing time was about 6 hours. The positive electrode active material was produced through the above steps. In Example 1, the composition of the positive electrode active material is LiNi _0.5 Mn _1.5 O ₄ . The average particle diameter of the positive electrode active material (arithmetic average value of the equivalent sphere diameter) was calculated by analyzing the SEM image. That is, the sphere equivalent diameters of a plurality of positive electrode active materials were calculated based on SEM images, and the arithmetic average value thereof was taken as the average particle diameter. As a result, the average particle size was 7 μm.

(1-2. Production of coin half cell)
A coin half cell was manufactured by the following process. First, natural graphite (manufactured by Nippon Graphite Industry Co., Ltd.), styrene butadiene rubber (SBR), and CMC weighed at a mass ratio of 1: 1: 1 were dispersed in ion-exchanged water to form a slurry. Subsequently, this slurry was applied onto an aluminum foil to be the positive electrode current collector 21, and dried to form a coating layer 21a on the aluminum foil. Here, the density | concentration and coating amount of the natural graphite in a slurry were adjusted so that the surface density of the natural graphite in the coating layer 21a might be 0.07 mg / cm < ² >. The thickness of the coating layer 21a was 0.5 μm.

Subsequently, the positive electrode active material, acetylene black (manufactured by Denka) having a BET specific surface area of 133 m ² / g, and polyvinylidene fluoride were mixed at a mass ratio of 95: 2: 3. The BET specific surface area was measured with a high-accuracy and multi-analyte gas adsorption amount measuring apparatus (Aotosorb, Canterchrome Instruments). This mixture (positive electrode mixture) was dispersed in N-methyl-2-pyrrolidone to form a slurry. The positive electrode active material layer 22 was formed by applying the slurry onto the coating layer 21a and drying the slurry. And the positive electrode 20 was produced by rolling so that the thickness of the positive electrode active material layer 22 might be set to 50 micrometers.

  The negative electrode 30 was produced by placing a metal lithium foil on a copper foil as the negative electrode current collector 31. Then, a porous polypropylene film having a thickness of 12 μm as a separator (magnesium hydroxide coating on both sides; manufactured by Teijin Ltd.) is prepared, and the separator is disposed between the positive electrode 20 and the negative electrode 30 to form an electrode. A structure was produced. Next, the electrode structure was processed into the size of a coin half cell and stored in a coin half cell container.

Next, lithium hexafluorophosphate (LiPF ₆ ) is added to a non-aqueous solvent in which fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), and hydrofluoroether (HFE) are mixed at a volume ratio of 2: 3: 5. An electrolytic solution was produced by dissolving at a concentration of 15M.

(1-3. Charge / discharge treatment)
The half cells were charged / discharged at the charge / discharge rate shown in Table 1 below. CC-CV means constant current and constant voltage, and CC means constant current. The temperature during charging and discharging was 45 ° C. The cut-off voltage was 3.0 to 4.9 V (Li / Li ⁺ ). However, charging at the 63rd cycle was cut off at 1/20 * C.

  The discharge capacity at the second cycle was taken as the discharge capacity of Example 1. A value obtained by dividing the discharge capacity at the sixth cycle by the discharge capacity at the third cycle (5 C / 0.5 C) was defined as the discharge load characteristic. A value (5C / 0.5C) obtained by dividing the charge capacity at the 11th cycle by the charge capacity at the 8th cycle was defined as the charge load characteristic. A value obtained by dividing the discharge capacity at the 63rd cycle by the discharge capacity at the 14th cycle was defined as a cycle life (so-called capacity maintenance ratio). The results are summarized in Table 2.

<2. Example 2>
The same treatment as in Example 1 was performed except that the conductive auxiliary was acetylene black (manufactured by Denka) having a BET specific surface area of 125 m ² / g. The results are summarized in Table 2.

<3. Example 3>
The same treatment as in Example 1 was performed except that the conductive auxiliary was acetylene black (manufactured by Denka) having a BET specific surface area of 39 m ² / g. The results are summarized in Table 2.

<4. Example 4>
In addition to nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and manganese sulfate pentahydrate (MnSO ₄ · 5H ₂ O), aluminum sulfate 16 hydrate (Al ₂ (SO ₄ ) ₃ · 16H ₂ O ) other using, by performing the same process as in example ₁ to prepare a cathode active material represented by _{Li 1.03 Ni 0.5 Mn 1.45 Al 0.05} O 4. Further, acetylene black (manufactured by Denka) having a BET specific surface area of 125 m ² / g was used as a conductive aid. The other processes were the same as in Example 1. The results are summarized in Table 2.

<5. Example 5>
In addition to nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and manganese sulfate pentahydrate (MnSO ₄ · 5H ₂ O), aluminum sulfate 16 hydrate (Al ₂ (SO ₄ ) ₃ · 16H ₂ O ) other using, by performing the same process as in example ₁ to prepare a cathode active material represented by _{Li 1.03 Ni 0.5 Mn 1.49 Al 0.01} O 4. Further, acetylene black (manufactured by Denka) having a BET specific surface area of 125 m ² / g was used as a conductive aid. The other processes were the same as in Example 1. The results are summarized in Table 2.

<6. Example 6>
In addition to nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and manganese sulfate pentahydrate (MnSO ₄ · 5H ₂ O), copper sulfate pentahydrate (CuSO ₄ · 5H ₂ O) was used. , by performing the same process as in example ₁ to prepare a cathode active material represented by _{Li 1.03 Ni 0.5 Mn 1.45 Cu 0.01} O 4. Further, acetylene black (manufactured by Denka) having a BET specific surface area of 125 m ² / g was used as a conductive aid. The other processes were the same as in Example 1. The results are summarized in Table 2.

<7. Example 7>
In addition to nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and manganese sulfate pentahydrate (MnSO ₄ · 5H ₂ O), zinc sulfate heptahydrate (ZnSO ₄ · 7H ₂ O) was used. , by performing the same process as in example ₁ to prepare a cathode active material represented by _{Li 1.03 Ni 0.5 Mn 1.49 Zn 0.02} O 4. Further, acetylene black (manufactured by Denka) having a BET specific surface area of 125 m ² / g was used as a conductive aid. The other processes were the same as in Example 1. The results are summarized in Table 2.

<8. Example 8>
In addition to nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and manganese sulfate pentahydrate (MnSO ₄ · 5H ₂ O), zinc sulfate heptahydrate (ZnSO ₄ · 7H ₂ O) was used. , by performing the same process as in example ₁ to prepare a cathode active material represented by _{Li 1.03 Ni 0.5 Mn 1.49 Zn 0.01} O 4. Further, acetylene black (manufactured by Denka) having a BET specific surface area of 125 m ² / g was used as a conductive aid. The other processes were the same as in Example 1. The results are summarized in Table 2.

<9. Example 9>
The same treatment as in Example 1 was performed except that the conductive auxiliary was acetylene black (manufactured by Denka) having a BET specific surface area of 206 m ² / g. The results are summarized in Table 2.

<10. Example 10>
The same treatment as in Example 1 was performed except that the conductive auxiliary was acetylene black (manufactured by Denka) having a BET specific surface area of 215 m ² / g. The results are summarized in Table 2.

<11. Comparative Example 1>
The same treatment as in Example 1 was performed except that the coating layer 21a was not provided. The results are summarized in Table 2.

<12. Comparative Example 2>
The same treatment as in Example 2 was performed except that the coating layer 21a was not provided. The results are summarized in Table 2.

<13. Comparative Example 3>
The same treatment as in Example 4 was performed except that the coating layer 21a was not provided. The results are summarized in Table 2.

<14. Comparative Example 4>
The same treatment as in Example 6 was performed except that the coating layer 21a was not provided. The results are summarized in Table 2.

<15. Comparative Example 5>
The same treatment as in Example 7 was performed except that the coating layer 21a was not provided. The results are summarized in Table 2.

<16. Comparative Example 6>
The same treatment as in Example 8 was performed except that the coating layer 21a was not provided. The results are summarized in Table 2.

<17. Comparative Example 7>
The same treatment as in Example 1 was performed except that the conductive auxiliary was Furnace Black (manufactured by Lion Specialty Chemicals) with a BET specific surface area of 377 m ² / g. The results are summarized in Table 2.

<18. Comparative Example 8>
The same treatment as in Example 1 was performed except that the conductive auxiliary was furnace black (manufactured by Lion Specialty Chemicals) with a BET specific surface area of 800 m ² / g. The results are summarized in Table 2.

<19. Comparative Example 9>
In Comparative Example 9, a positive electrode active material was prepared by the following process. First, cobalt sulfate pentahydrate was dissolved in ion exchange water to produce a mixed aqueous solution. Here, the mass of cobalt sulfate pentahydrate was 20 mass% with respect to the total mass of the mixed aqueous solution.

  Moreover, 500 ml of ion exchange water was added to the reaction layer, and the temperature of this ion exchange water was maintained at 50 ° C. And 40 mass% NaOH aqueous solution was dripped at ion-exchange water, and pH of reaction layer aqueous solution was adjusted to 11.5. Next, dissolved oxygen was removed by bubbling ion exchange water with nitrogen gas.

  Then, while stirring the reaction layer aqueous solution and maintaining the temperature of the reaction layer aqueous solution at 50 ° C., the above-described mixed aqueous solution was dropped into the reaction layer aqueous solution at a rate of 3 ml / min.

In addition to the mixed aqueous solution, a 40% by mass NaOH aqueous solution and a 10% by mass NH ₃ aqueous solution were dropped into the reaction tank aqueous solution to maintain the pH of the aqueous reaction layer solution at 11.5. Here, the stirring speed was 4 to 5 m / s in peripheral speed, and the stirring time was 10 hours. Thereby, cobalt hydroxide precipitated.

  Subsequently, cobalt hydroxide was taken out from the aqueous reaction layer solution by suction filtration, and the cobalt hydroxide was washed with ion-exchanged water. And cobalt hydroxide was vacuum-dried. The temperature for vacuum drying was 100 ° C., and the drying time was 10 hours.

Next, the dried cobalt hydroxide was pulverized in a mortar for several minutes to obtain a dry powder. And dry powder, lithium carbonate (Li ₂ CO ₃ ), aluminum nitrate nonahydrate (Al (NO ₃ ) ₃ .9H ₂ O), magnesium nitrate hexahydrate (Mg (NO ₃ ) ₂ .6H ₂ O) was mixed to produce a mixed powder. Here, the molar ratio of Li, Co, Al, and Mg was 1.03: 0.98: 0.01: 0.01.

Further, this mixed powder was fired at 970 ° C. for 10 hours. Through the above steps, a positive electrode active material according to Comparative Example 9 was produced. The composition of the positive electrode active material is Li _1.03 Co _0.98 Al _0.01 Mg _0.01 O ₂ . Therefore, the positive electrode active material becomes a lithium cobaltate-based positive electrode active material. Since this positive electrode active material does not have a spinel crystal structure, charging and discharging under a high voltage cannot be performed. It was 13 micrometers when the average particle diameter (arithmetic mean value of the sphere equivalent diameter) of the positive electrode active material was measured by the method described above. The same treatment as in Example 2 was performed except that this positive electrode active material was used. However, the cut-off voltage was set to 3.0 to 4.6 V (Li / Li ⁺ ). The results are summarized in Table 2.

<20. Comparative Example 10>
The same treatment as in Comparative Example 9 was performed except that the coating layer 21a was not provided. The results are summarized in Table 2.

<21. Comparative Example 11>
In Comparative Example 11, a positive electrode active material was produced by the following process. First, nickel sulfate hexahydrate, manganese sulfate heptahydrate, and cobalt sulfate pentahydrate were dissolved in ion-exchanged water to produce a mixed aqueous solution. Here, the total mass of nickel sulfate hexahydrate, manganese sulfate heptahydrate, and cobalt sulfate pentahydrate was 20 mass% with respect to the total mass of the mixed aqueous solution. In addition, nickel sulfate hexahydrate, manganese sulfate heptahydrate, and cobalt sulfate pentahydrate have a molar ratio Ni: Co: Mn of Ni, Co, and Mn of 20:20:60. Mixed.

  Moreover, 500 ml of ion exchange water was added to the reaction layer, and the temperature of this ion exchange water was maintained at 50 ° C. And 40 mass% NaOH aqueous solution was dripped at ion-exchange water, and pH of reaction layer aqueous solution was adjusted to 11.5. Next, dissolved oxygen was removed by bubbling ion exchange water with nitrogen gas.

  Then, while stirring the reaction layer aqueous solution and maintaining the temperature of the reaction layer aqueous solution at 50 ° C., the above-described mixed aqueous solution was dropped into the reaction layer aqueous solution at a rate of 3 ml / min.

In addition to the mixed aqueous solution, a 40% by mass NaOH aqueous solution and a 10% by mass NH ₃ aqueous solution were dropped into the reaction tank aqueous solution to maintain the pH of the aqueous reaction layer solution at 11.5. Here, the stirring speed was 4 to 5 m / s in peripheral speed, and the stirring time was 10 hours. Thereby, the hydroxide of each metal element coprecipitated.

  Subsequently, the coprecipitated hydroxide was taken out from the reaction layer aqueous solution by suction filtration, and the coprecipitated hydroxide was washed with ion-exchanged water. The coprecipitated hydroxide was vacuum dried. The temperature for vacuum drying was 100 ° C., and the drying time was 10 hours.

Next, the dried coprecipitated hydroxide was pulverized for several minutes in a mortar to obtain a dry powder. Then, a dry powder, by mixing a lithium carbonate _(Li 2 CO _3), to produce a mixed powder. Here, the molar ratio between Li and M (= Ni + Mn + Co) was 1.4: 1.

Further, this mixed powder was fired at 800 ° C. for 10 hours. Through the above steps, the positive electrode active material according to Comparative Example 11 was produced. The composition of the positive electrode active material is 0.4Li ₂ MnO ₃ —0.6Li (Ni _0.33 Co _0.33 Mn _0.33 ) O ₂ . Therefore, the positive electrode active material becomes a solid solution type positive electrode active material. Since this positive electrode active material does not have a spinel crystal structure, charging and discharging under a high voltage cannot be performed. The average particle diameter (arithmetic average value of equivalent sphere diameters) of the positive electrode active material was measured by the method described above, and it was 7 μm. The same treatment as in Example 2 was performed except that this positive electrode active material was used. However, the cut-off voltage was 2.5 to 4.6 V (Li / Li ⁺ ). The results are summarized in Table 2.

<22. Comparative Example 12>
The same treatment as in Comparative Example 11 was performed except that the coating layer 21a was not provided. The results are summarized in Table 2.

<23. Contrast>
First, when Examples 1 to 10 and Comparative Examples 1 to 6 were compared, the cycle life of Examples 1 to 10 was significantly improved as compared with Comparative Examples 1 to 6. Rather, in Comparative Examples 1 to 6, the cycle life deteriorated rapidly, so that a significant value could not be obtained. In Comparative Examples 1 to 6, since the positive electrode current collector 21 is not covered with the coating layer 21a, it is considered that aluminum ions were eluted from the positive electrode current collector 21 during charging and discharging. In Comparative Examples 1 to 6, it is presumed that a passive film is formed on the positive electrode current collector 21 by charge and discharge in the first cycle, but aluminum ions are also eluted by such a passive film. It became clear that it could not be suppressed. And it is thought that this aluminum ion precipitated on the negative electrode and deteriorated cycle life remarkably. On the other hand, in Examples 1-10, since the positive electrode electrical power collector 21 was covered with the coating layer 21a, it is thought that the elution of aluminum ion could be suppressed. Therefore, by combining the positive electrode active material having a spinel crystal structure and the positive electrode current collector 21 covered with the coating layer 21a, a high energy density can be realized and the cycle life is greatly improved.

Next, when Examples 1, 2, 4 to 10 were compared with Example 3, Examples 1, 2, 4 to 10 were superior in cycle life to Example 3. Examples 1, 2, 4 to 10 and Example 3 differ in the BET specific surface area of the conductive additive. Further, when Examples 1 to 10 and Comparative Examples 7 and 8 are compared, Examples 1 to 10 and Comparative Examples 7 and 8 have different BET specific surface areas of the conductive assistant. Therefore, the BET specific surface area of the conductive auxiliary agent needs to be 35 to 350 m ² / g. BET specific surface area is preferably 45~350m ² / g, more preferably 100 to 300 m ² / g, more preferably 120~220m ² / g.

  Next, focusing on Comparative Examples 9 and 10, in Comparative Examples 9 and 10, the cycle life was greatly deteriorated as compared with Examples 1-10. Since the positive electrode active materials of Comparative Examples 9 and 10 are not suitable for use under high voltage, it is considered that the cycle life is greatly deteriorated. If the charge / discharge voltage is set to the same level as in Examples 1 to 10, it can be easily estimated that the cycle life is further deteriorated. For this reason, in Comparative Examples 9 and 10, since it is necessary to perform charging and discharging under a low voltage as compared with Examples 1 to 10, the energy density is reduced. In Comparative Examples 9 and 10, no change in the cycle life due to the presence or absence of the coating layer 21a was observed. In Comparative Examples 9 and 10, since charging / discharging is performed under a lower voltage than in Examples 1 to 10, it is presumed that the elution of aluminum ions did not increase so much. Thus, the coating layer 21a can obtain a remarkable effect when combined with the positive electrode active material having a spinel crystal structure.

  Next, focusing on Comparative Examples 11 and 12, the cycle life of Comparative Examples 11 and 12 was better than Comparative Examples 9 and 10. However, the cycle life of Comparative Examples 11 and 12 was deteriorated as compared with Examples 1-10. Since the positive electrode active materials of Comparative Examples 11 and 12 are not suitable for use under a high voltage, it is considered that the cycle life is deteriorated. If the charge / discharge voltage is set to the same level as in Examples 1 to 10, it can be easily estimated that the cycle life is further deteriorated. For this reason, in Comparative Examples 11 and 12, since it is necessary to perform charging and discharging under a low voltage as compared with Examples 1 to 10, the energy density is reduced. In Comparative Examples 11 and 12, no change in cycle life due to the presence or absence of the coating layer 21a was observed. In Comparative Examples 11 and 12, since charging / discharging was performed under a lower voltage than in Examples 1 to 10, it is estimated that the elution of aluminum ions did not increase so much. Thus, the coating layer 21a can obtain a remarkable effect when combined with the positive electrode active material having a spinel crystal structure.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery 20 Positive electrode 21 Positive electrode collector 21a Coating layer 22 Positive electrode active material layer 30 Negative electrode 31 Negative electrode collector 32 Negative electrode active material layer 40 Separator layer

Claims (9)

A positive electrode current collector;
A coating layer containing graphite and covering the positive electrode current collector;
A positive electrode active material having a composition represented by the following chemical formula 1;
And a conductive additive having a BET specific surface area of 35 to 350 m ² / g.
Li _x Ni _y Mn _2-yz M _z O ₄ (1)
In the chemical formula 1, M is any one or more metal elements selected from a specific transition metal and aluminum,
The specific transition metal is a transition metal excluding nickel and manganese,
x, y, and z are values within the ranges of 0.02 ≦ x ≦ 1.10, 0.25 ≦ y ≦ 0.6, and 0.0 <z ≦ 0.10.   In Formula 1, M is aluminum (Al), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum ( 1 selected from the group consisting of Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce). The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode is a seed or two or more metal elements.   3. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein y in the chemical formula 1 is a value within a range of 0.40 ≦ y <0.60. BET specific surface area of the conductive additive is characterized in that it is a 45~350m 2 / ^g, the non-aqueous electrolyte secondary battery positive electrode according to any one of claims 1-3. 5. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the conductive auxiliary agent has a BET specific surface area of 100 to 300 m ² / g. 6. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the conductive auxiliary agent has a BET specific surface area of 120 to 220 m ² / g.   The positive electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the conductive auxiliary agent contains carbon black.   A nonaqueous electrolyte secondary battery comprising the positive electrode for a nonaqueous electrolyte secondary battery according to claim 1.   9. The nonaqueous electrolyte secondary battery according to claim 8, comprising at least one fluoro nonaqueous solvent as a solvent for the electrolytic solution.

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