JP2014203589A - Positive electrode active material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material for a nonaqueous electrolyte secondary battery, exhibiting excellent rate characteristics and cycle characteristics, and a nonaqueous electrolyte secondary battery having a positive electrode using the positive electrode active material.SOLUTION: A positive electrode active material for a nonaqueous electrolyte secondary battery contains at least one or more oxides selected from the group consisting of oxides represented by the following formula (I) and oxides represented by the following formula (II), and contains 10 ppm or more and 1,000 ppm or less, per one element, of at least one or more elements selected from the group consisting of Si, Fe and Cr, relative to the mass of the positive electrode active material. (I) LiMO(in the formula (I), M represents one or more metal elements, and x satisfies -0.2<x<0.3.) (II) LiMnM'O(in the formula (II), M' represents one or more metal elements other than Mn, and x and y satisfy -0.2<x<0.3 and 0≤y<2.)

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery having a positive electrode using the same.

  With the recent development of electronic technology and increasing interest in environmental technology, various electrochemical devices are used. In particular, there are many requests for energy saving, and expectations for electrochemical devices that can contribute to energy saving are increasing. Lithium ion secondary batteries, which are representative examples of power storage devices and also representative examples of non-aqueous electrolyte secondary batteries, have been used mainly as rechargeable batteries for portable devices. However, in recent years, batteries for hybrid vehicles and electric vehicles have been used. The use as is expected.

  However, when a lithium ion secondary battery is used in an automotive application, use with a larger current and a longer life are required than when used for a conventional portable device. However, the current nonaqueous electrolyte secondary battery has not yet achieved sufficient characteristics.

  In Patent Document 1, when the total amount of at least one alkaline earth metal selected from Mg, Ca, and Ba is 120 ppm or more and 5000 ppm or less with respect to the entire positive electrode active material, good cycle characteristics can be obtained. It is disclosed.

Japanese Patent No. 3959801

  However, Patent Document 1 does not describe rate characteristics. The rate characteristic is a characteristic that can be used even when the battery is discharged with a large current. For example, the rate characteristic is important in order to achieve the effect of quickly accelerating when starting in an automobile application. At the same time, it is important to have excellent cycle characteristics. Therefore, there is still room for improvement in the prior art.

  The present invention has been made in view of the above problems, and has a positive electrode active material for a non-aqueous electrolyte secondary battery that exhibits excellent rate characteristics and cycle characteristics, and a non-aqueous electrolyte secondary having a positive electrode using the same. Provide batteries.

  As a result of intensive studies to solve the above problems, the present inventors have found that a group consisting of elements such as Si, Fe, and Cr in a positive electrode active material of a lithium composite oxide used in a non-aqueous electrolyte secondary battery. It has been found that the above problems can be solved if the positive electrode active material contains a predetermined amount of at least one element selected from the above, and the present invention has been accomplished.

That is, the present invention is as follows.
[1]
Including at least one oxide selected from the group consisting of an oxide represented by the following formula (I) and an oxide represented by the formula (II),
Containing at least one element selected from the group consisting of Si, Fe, and Cr, in an amount of 10 ppm or more and 1000 ppm or less per element with respect to the mass of the positive electrode active material;
Positive electrode active material for non-aqueous electrolyte secondary battery.
(I) Li1 + xMO2
(In formula (I), M represents one or more metal elements, and x satisfies −0.2 <x <0.3.)
(II) Li1 + xMn2-yM'yO4
(In formula (II), M ′ represents one or more metal elements other than Mn, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <2.)
[2]
An oxide represented by the following formula (III):
Containing at least one element selected from the group consisting of Si and Cr, with respect to the mass of the positive electrode active material, of 10 ppm or more and 1000 ppm or less per element,
Positive electrode active material for non-aqueous electrolyte secondary battery.
(III) Li1 + xFe1-yM''yPO4
(In formula (III), M ″ represents one or more metal elements other than Fe, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <1.)
[3]
Including at least one oxide selected from the group consisting of an oxide represented by the following formula (IV), an oxide represented by the formula (V), and an oxide represented by the formula (IV),
A positive electrode active material for a non-aqueous electrolyte secondary battery containing at least one element selected from the group consisting of Na, K, Cl, and S with respect to the positive electrode active material mass of 10 ppm or more and 2000 ppm or less per element .
(IV) Li1 + xMO2
(In formula (IV), M represents one or more metal elements, and x satisfies −0.2 <x <0.3.)
(V) Li1 + xMn2-yM'yO4
(In Formula (V), M ′ represents one or more metal elements other than Mn, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <2.)
(IV) Li1 + xFe1-yM''yPO4
(In formula (IV), M ″ represents one or more metal elements other than Fe, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <1.)
[4]
A nonaqueous electrolyte secondary battery having a positive electrode comprising the positive electrode active material according to any one of [1] to [3].

  The positive electrode active material for a non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention exhibits excellent rate characteristics and cycle characteristics.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof.

[Positive electrode active material for nonaqueous electrolyte secondary battery of first form]
The positive electrode active material for a nonaqueous electrolyte secondary battery according to the first embodiment (hereinafter, also simply referred to as “positive electrode active material”) is
Including at least one oxide selected from the group consisting of an oxide represented by the following formula (I) and an oxide represented by the formula (II),
At least one element selected from the group consisting of Si, Fe, and Cr is included at 10 ppm or more and 1000 ppm or less per element with respect to the mass of the positive electrode active material.
(I) Li _{1 + x} MO ₂
(In formula (I), M represents one or more metal elements, and x satisfies −0.2 <x <0.3.)
(II) Li _{1 + x} Mn _2-y M ′ _y O ₄
(In formula (II), M ′ represents one or more metal elements other than Mn, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <2.)

[Oxide]
The positive electrode active material according to the first embodiment of the present embodiment includes at least one or more kinds selected from the group consisting of an oxide represented by the formula (I) and a spinel oxide represented by the formula (II). Contains oxides. These oxides can electrochemically occlude and release lithium ions.

  M represents one or more metal elements and is not particularly limited. For example, Ni, Mn, Co, Fe, Cr, V, Ti, Cu, Zr, Al, In, Sn, B, Mg, Si, Ge, Ga, Y, La, Ce, Pr, Nd, Sm, Zn, Na, Ca, Nb, Sr, Ba, Cd, and Li are shown. Among these, Ni, Mn, Co, Fe, Cr, V, Ti, Zr, Al, In, Sn, B, Mg, Si, Ge, Ga, Y, Ce, Zn, Na, Ca, Nb, and Li are included. preferable. By using such a metal element, it tends to exhibit more excellent rate characteristics and cycle characteristics.

  M ′ represents one or more metal elements other than Mn and is not particularly limited. For example, Ni, Co, Fe, Cr, V, Ti, Cu, Zr, Al, In, Sn, B, Mg, Si, Ge , Ga, Y, La, Ce, Pr, Nd, Sm, Zn, Na, Ca, Nb, Sr, Ba, Cd, Li are shown. Among these, Ni, Co, Fe, Cr, V, Ti, Zr, Al, In, Sn, B, Mg, Si, Ge, Ga, Y, Ce, Zn, Na, Ca, Nb, and Li are preferable. By using such a metal element, it tends to exhibit more excellent rate characteristics and cycle characteristics.

[Additive elements]
In the first embodiment of the positive electrode active material according to the present embodiment, at least one element selected from the group consisting of Si, Fe, and Cr is 10 ppm or more and 1000 ppm per element with respect to the mass of the positive electrode active material. It is preferably contained in an amount of 10 ppm or more and 800 ppm or less per element, more preferably 20 ppm or more and 800 ppm or less per element. By including at least one element selected from the group consisting of Si, Fe, and Cr within the above range, more excellent rate characteristics and cycle characteristics are exhibited.

  In the positive electrode active material of the first form according to the present embodiment, in addition to the above elements, at least one element selected from the group consisting of Na, K, Cl, and S is included in the positive electrode active material mass. It is preferable to contain 10 ppm or more and 2000 ppm or less per element, more preferably 10 ppm or more and 1500 ppm or less per element, and further preferably 20 ppm or more and 1500 ppm or less per element. By including at least one element selected from the group consisting of Na, K, Cl, and S within the above range, it tends to exhibit more excellent rate characteristics and cycle characteristics.

  At least one element selected from the group consisting of Si, Fe, and Cr, or in addition to the element, at least one element selected from the group consisting of Na, K, Cl, and S Is not particularly limited, and any known method can be used. For example, by using at least one or more selected from the group consisting of the element itself and a gas, liquid, or solid compound containing the element, a positive electrode manufactured or added to a raw material or a firing atmosphere when manufacturing a positive electrode active material It can be included by adding to the active material later.

  The reason why the nonaqueous electrolyte secondary battery using the positive electrode active material according to the first embodiment of the present embodiment has excellent rate characteristics and cycle characteristics is unknown in detail. However, excellent rate characteristics and cycle characteristics can be achieved by improving the conductivity by doping the positive electrode active material with the above elements and reducing the side reaction of the electrolytic solution by covering the surface of the positive electrode active material with the above elements. It is thought that it is demonstrated.

  If the above element exceeds the upper limit of the content, the rate characteristics and the cycle characteristics deteriorate. The reason for this is unknown in detail, but it is thought that the battery characteristics deteriorate due to segregation at the crystal interface or the occurrence of a heterogeneous phase in the positive electrode active material to become a resistance component.

In addition to the oxide, the positive electrode active material of the first form according to the present embodiment can include known materials that can electrochemically occlude and release lithium ions. Among these, as the positive electrode active material, a material containing lithium is preferable. Although it does not specifically limit as such a material, For example, it is complex oxide of the oxide represented by following formula (7), and the oxide represented by following formula (8), Comprising: ) Or a compound represented by the following formula (10). These compounds may be used alone or in combination of two or more.
Li ₂ MaO ₃ (7)
(In the formula, Ma represents at least one element selected from the group consisting of transition metal elements.)
LiMbO ₂ (8)
(In the formula, Mb represents at least one element selected from the group consisting of transition metal elements.)
_{zLi 2 MaO 3 - (1-} z) LiMbO 2 (9)
(In the formula, Ma and Mb are synonymous with those in the above formulas (7) and (8), respectively, and 0.1 ≦ z ≦ 0.9.)
Li ₂ McPO ₄ F (10)
(In the formula, Mc represents at least one element selected from the group consisting of transition metal elements.)

[Positive electrode active material for nonaqueous electrolyte secondary battery of second form]
Further, the positive electrode active material for a nonaqueous electrolyte secondary battery according to the second embodiment (hereinafter also simply referred to as “positive electrode active material”) includes an oxide represented by the following formula (III). And at least one element selected from the group consisting of Si, Cr and 10 ppm or more and 1000 ppm or less per element with respect to the mass of the positive electrode active material.
(III) Li _{1 + x} Fe _1-y M ″ _y PO ₄
(In formula (III), M ″ represents one or more metal elements other than Fe, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <1.)

[Oxide]
The positive electrode active material of the 2nd form which concerns on this embodiment contains the olivine type oxide represented by Formula (III). The oxide is capable of electrochemically inserting and extracting lithium ions.

  M ″ represents one or more metal elements other than Fe, and is not particularly limited. For example, Ni, Mn, Co, Cr, V, Ti, Cu, Zr, Al, In, Sn, B, Mg, Si , Ge, Ga, Y, La, Ce, Pr, Nd, Sm, Zn, Na, Ca, Nb, Sr, Ba, Cd, Li are shown. Among these, Ni, Mn, Co, Cr, V, Ti, Zr, Al, In, Sn, B, Mg, Si, Ge, Ga, Y, Ce, Zn, Na, Ca, Nb, and Li are preferable. By using such a metal element, it tends to exhibit more excellent rate characteristics and cycle characteristics.

[Additive elements]
The positive electrode active material according to the second embodiment of the present embodiment includes at least one element selected from the group consisting of Si and Cr, in an amount of 10 ppm or more and 1000 ppm or less per element with respect to the mass of the positive electrode active material. It is preferably 10 ppm or more and 800 ppm or less per element, and more preferably 20 ppm or more and 800 ppm or less per element. By including at least one element selected from the group consisting of Si and Cr within the above range, more excellent rate characteristics and cycle characteristics are exhibited.

  In the positive electrode active material according to the second embodiment of the present embodiment, in addition to the above elements, at least one element selected from the group consisting of Na, K, Cl, and S is added to the positive electrode active material mass. It is preferable to contain 10 ppm or more and 2000 ppm or less per element, more preferably 10 ppm or more and 1500 ppm or less per element, and further preferably 20 ppm or more and 1500 ppm or less per element. By including at least one element selected from the group consisting of Na, K, Cl, and S within the above range, it tends to exhibit more excellent rate characteristics and cycle characteristics.

  At least one element selected from the group consisting of Si and Cr, or in addition to the element, at least one element selected from the group consisting of Na, K, Cl, and S, It does not specifically limit as a method to include in a positive electrode active material, All the well-known methods can be used. For example, by using at least one or more selected from the group consisting of the element itself and a gas, liquid, or solid compound containing the element, a positive electrode manufactured or added to a raw material or a firing atmosphere when manufacturing a positive electrode active material It can be included by adding to the active material later.

  The reason why the nonaqueous electrolyte secondary battery using the positive electrode active material according to the second embodiment of the present embodiment has excellent rate characteristics and cycle characteristics is unknown in detail. However, excellent rate characteristics and cycle characteristics can be achieved by improving the conductivity by doping the positive electrode active material with the above elements and reducing the side reaction of the electrolytic solution by covering the surface of the positive electrode active material with the above elements. It is thought that it is demonstrated.

  If the above element exceeds the upper limit of the content, the rate characteristics and the cycle characteristics deteriorate. The reason for this is unknown in detail, but it is thought that the battery characteristics deteriorate due to segregation at the crystal interface or the occurrence of a heterogeneous phase in the positive electrode active material to become a resistance component.

  In addition to the above oxide, the positive electrode active material of the second form according to the present embodiment can include other known materials that can electrochemically occlude and release lithium ions. Among these, as the positive electrode active material, a material containing lithium is preferable. Although it does not specifically limit as such a material, For example, the compound represented by Formula (9) and (10) is mentioned.

[Positive electrode active material for nonaqueous electrolyte secondary battery of third form]
Furthermore, the positive electrode active material for a nonaqueous electrolyte secondary battery according to the third embodiment of the present embodiment includes an oxide represented by the following formula (IV), an oxide represented by the formula (V), and a formula ( IV) at least one oxide selected from the group consisting of oxides represented by
At least one element selected from the group consisting of Na, K, Cl, and S is contained at 10 ppm or more and 2000 ppm or less per element with respect to the mass of the positive electrode active material.
(IV) Li _{1 + x} MO ₂
(In formula (IV), M represents one or more metal elements, and x satisfies −0.2 <x <0.3.)
(V) Li _{1 + x} Mn _2-y M ′ _y O ₄
(In Formula (V), M ′ represents one or more metal elements other than Mn, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <2.)
(IV) Li _{1 + x} Fe _1-y M ″ _y PO ₄
(In formula (IV), M ″ represents one or more metal elements other than Fe, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <1.)

[Oxide]
The positive electrode active material according to the third embodiment of the present embodiment includes an oxide represented by the formula (IV), an oxide represented by the formula (V), and an oxide represented by the formula (IV). It contains at least one oxide selected from the group. As these oxides, oxides represented by the formula (I), oxides represented by the formula (II), and oxides represented by the formula (III) can be used.

[Additive elements]
The positive electrode active material according to the third embodiment of the present embodiment includes at least one element selected from the group consisting of Na, K, Cl, and S at least 10 ppm per element with respect to the positive electrode active material mass. , 2000 ppm or less, preferably 10 ppm or more and 1500 ppm or less per element, more preferably 20 ppm or more and 1500 ppm or less per element. By including at least one element selected from the group consisting of Na, K, Cl and S within the above range, more excellent rate characteristics and cycle characteristics are exhibited.

  The method for including at least one element selected from the group consisting of Na, K, Cl, and S in the positive electrode active material is not particularly limited, and all known methods can be used. For example, by using at least one or more selected from the group consisting of the element itself and a gas, liquid, or solid compound containing the element, a positive electrode manufactured or added to a raw material or a firing atmosphere when manufacturing a positive electrode active material It can be included by adding to the active material later.

  The reason why the nonaqueous electrolyte secondary battery using the positive electrode active material according to the third embodiment of the present embodiment has excellent rate characteristics and cycle characteristics is unknown in detail. However, excellent rate characteristics and cycle characteristics can be achieved by improving the conductivity by doping the positive electrode active material with the above elements and reducing the side reaction of the electrolytic solution by covering the surface of the positive electrode active material with the above elements. It is thought that it is demonstrated.

  If the above element exceeds the upper limit of the content, the rate characteristics and the cycle characteristics deteriorate. The reason for this is unknown in detail, but it is thought that the battery characteristics deteriorate due to segregation at the crystal interface or the occurrence of a heterogeneous phase in the positive electrode active material to become a resistance component.

  In addition to the oxide, the positive electrode active material of the third mode according to the present embodiment can include other known materials that can electrochemically occlude and release lithium ions. Among these, as the positive electrode active material, a material containing lithium is preferable. Although it does not specifically limit as such a material, For example, the compound represented by Formula (9) and (10) is mentioned.

[Nonaqueous electrolyte secondary battery]
The nonaqueous electrolyte secondary battery according to this embodiment has a positive electrode containing the positive electrode active material. In addition, the nonaqueous electrolyte secondary battery may have a negative electrode, a nonaqueous electrolyte, a separator, an exterior body, and the like. Such a nonaqueous electrolyte secondary battery has excellent rate characteristics and cycle characteristics.

[Positive electrode]
The positive electrode used for the nonaqueous electrolyte secondary battery according to the present embodiment preferably includes the positive electrode active material, a conductive material, a binder (binder), and a current collector.

(Conductive material)
As the conductive material that can be included in the positive electrode, a known material that can conduct electrons can be used. Among them, the conductive material is not particularly limited. For example, non-graphitic carbonaceous materials such as activated carbon, various cokes, carbon black, and acetylene black; and metal powders such as graphite, aluminum, titanium, and stainless steel are preferable. These may be used alone or in combination of two or more.

(Binder (binder))
As a binder (binder) that can be included in the positive electrode, a known material that can bind at least two selected from the group consisting of a positive electrode active material, a conductive material that can be included in the positive electrode, and a current collector that can be included in the positive electrode. Things can be used. Such a binder is not particularly limited, but for example, polyvinylidene fluoride and fluororubber are preferable. A binder may be used individually by 1 type, or may be used together 2 or more types.

  The solvent for dissolving the binder (binder) is not particularly limited. For example, any known solvent can be used as long as the solvent dissolves the binder (binder). Among these, N-methyl-2-pyrrolidone, ethyl acetate, ethyl cellosolve and the like are preferable. The solvent for dissolving the binder (binder) may be used alone or in combination of two or more.

(Current collector)
Although it does not specifically limit as a collector which can be contained in a positive electrode, For example, metal foil, such as aluminum, titanium, stainless steel; Expand metal, punch metal, foam metal, carbon cloth, and carbon paper are mentioned. These may be used alone or in combination of two or more.

[Negative electrode]
The negative electrode that can be used in the nonaqueous electrolyte secondary battery according to the present embodiment preferably includes a negative electrode active material, a binder (binder), and a current collector.

(Negative electrode active material)
As the negative electrode active material that can be contained in the negative electrode, a known material that can electrochemically occlude and release lithium ions can be used. Among them, the negative electrode active material is not particularly limited, but for example, carbon materials such as graphite powder, mesophase carbon fiber, and mesophase microspheres; and metals, alloys, oxides, and nitrides are preferable. These may be used alone or in combination of two or more.

(Binder (binder))
The binder (binder) that can be included in the negative electrode is a known material that can bind at least two selected from the group consisting of a negative electrode active material, a conductive material that can be included in the negative electrode, and a current collector that can be included in the negative electrode. Things can be used. The binder (binder) is not particularly limited, and for example, carboxymethyl cellulose, styrene-butadiene cross-linked rubber latex, acrylic latex and polyvinylidene fluoride are preferable. These may be used alone or in combination of two or more.

(Current collector)
Although it does not specifically limit as a collector which can be contained in a negative electrode, For example, metal foil, such as copper, nickel, and stainless steel; Expand metal, punch metal, foam metal, carbon cloth, and carbon paper are mentioned. These may be used alone or in combination of two or more.

[Non-aqueous electrolyte]
The electrolyte (salt) contained in the non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery according to this embodiment is not particularly limited, and a conventionally known one can be used. The electrolyte is not particularly limited, for example, LiPF ₆ (lithium _{hexafluorophosphate), LiCIO 4, LiAsF 6,} Li 2 SiF 6, LiOSO 2 C k F 2k + 1 [k is an integer of 1 to 8] _{, LiN (SO 2 C k F} 2k + 1) 2 [k is an integer of 1 to _{8], LiCF 3 SO 3, LiC 4} F 9 SO 3, Li (CF 3 SO 2) 3 C, LiBF 4, LiBF 3 (C ₂ F ₅ ), LiB (C ₆ F ₅ ) ₄ , LiB (C ₂ O ₄ ) ₂ , LiB (C ₆ H ₅ ) ₄ , LiPF _n (C _k F _{2k + 1} ) _6-n [n is 1 to 5 , K is an integer of 1 to 8], LiPF ₄ (C ₂ O ₄ ), and LiPF ₂ (C ₂ O ₄ ) ₂ . These electrolytes may be used alone or in combination of two or more. Among these, LiPF ₆ is preferable because excellent rate characteristics and cycle characteristics tend to be more excellent.

(Non-aqueous solvent)
It does not specifically limit as a non-aqueous solvent contained in a non-aqueous electrolyte, A conventionally well-known thing can be used. Although it does not specifically limit as a non-aqueous solvent, For example, an aprotic polar solvent is preferable. Although it does not specifically limit as an aprotic polar solvent, Specifically, ethylene carbonate, propylene carbonate, 1, 2- butylene carbonate, 2, 3- butylene carbonate, 1, 2- pentylene carbonate, 2, 3 -Cyclic carbonates such as pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene carbonate and 4,5-difluoroethylene carbonate; Lactones such as γ-ptyrolactone and γ-valerolactone; Cyclic sulfones such as sulfolane; Cyclic ethers such as tetrahydrofuran and dioxane Ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate -Chain carbonates such as boronate, dibutyl carbonate, ethylpropyl carbonate and methyl trifluoroethyl carbonate; Nitriles such as acetonitrile; Chain ethers such as dimethyl ether; Chain carboxylic acid esters such as methyl propionate; Chain ethers such as dimethoxyethane A carbonate compound is mentioned. These may be used alone or in combination of two or more.

  Note that the nonaqueous electrolyte of the present embodiment may be a liquid electrolyte or a solid electrolyte.

〔separator〕
The separator that can be used in the nonaqueous electrolyte secondary battery according to the present embodiment is not particularly limited, and conventionally known separators used in nonaqueous electrolyte secondary batteries can be used. The separator is not particularly limited, but for example, a microporous film of polyolefin resin such as polyethylene and polypropylene; a resin such as cellulose, aromatic polyamide, fluororesin and polyolefin; and one or two inorganic substances such as alumina and silica Structures such as non-woven fabric, papermaking, porous membrane and the like containing at least seeds; solid electrolyte films. Any separator may be used as long as it has a high ion permeability and has a function of electrically isolating the positive electrode and the negative electrode.

[Exterior body]
A conventionally well-known thing can be used for the exterior body used for this embodiment. Although it does not specifically limit as a material of an exterior body, For example, the laminate film which coat | covered metal, such as stainless steel, iron, and aluminum, and the surface of the metal with resin.

  The nonaqueous electrolyte secondary battery according to the present embodiment may have the same configuration as that of a conventionally known one except that it has the above-described configuration. Examples of the nonaqueous electrolyte secondary battery according to this embodiment include a lithium ion secondary battery and a lithium ion capacitor.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Example 1]
(Manufacture of positive electrode)
After mixing nickel hydroxide, manganese hydroxide and cobalt hydroxide as the positive electrode active material so that the molar ratio of metal elements is 1: 1: 1, iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) While being immersed in a 1 mol / L aqueous solution, the mixture was heated in air at a temperature of 150 ° C. for 1 hour, and further heated at a temperature of 350 ° C. for 1 hour to obtain a powder. The obtained powder and lithium hydroxide were mixed, heated at a temperature of 800 ° C. for 8 hours and then cooled to synthesize Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ . The synthesized powder was classified to obtain Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ having an average particle diameter of 15 μm. When the amount of Fe of the obtained Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ was determined by ICP analysis (manufactured by PerkinElmer, product name Optima 8300), it was 900 ppm. The results are shown in Table 1.

  For 100 parts by mass of the positive electrode active material obtained as described above, 2 parts by mass of graphite powder having an average particle size of 3.3 μm and 4 parts by mass of non-graphitic carbon powder having an average particle size of 0.04 μm are used as the conductive material. Combined to make a compound.

  This compound is dispersed in an N-methyl-2-pyrrolidone (hereinafter also referred to as “NMP”) solution containing 6 parts by mass of polyvinylidene fluoride with respect to the compound, and a dispersion is prepared so that the solid content is 60% by mass. did.

This dispersion was coated on a 15 μm thick aluminum foil to a uniform thickness, and dried twice for each application. Thereafter, roll pressing was performed to produce a positive electrode. The coating amount of the obtained positive electrode was 490 g / m ^{2 on} both sides, and the bulk density of the active material was 2.4 g / cm ³ .

(Manufacture of negative electrode)
Next, natural graphite having an average particle diameter of 10 μm and artificial graphite having an average particle diameter of 5 μm were used as the negative electrode material. 1. 100 parts by mass of 90 parts by weight of natural graphite having an average particle diameter of 10 μm and 10 parts by weight of artificial graphite having an average particle diameter of 5 μm, 1.4 parts by weight of carboxymethylcellulose, and styrene / butadiene latex as a solid content. 8 parts by mass of each was mixed to form a dispersion using water as a dispersion medium. At this time, the solid content concentration of the dispersion was 50% by mass. This was coated on a copper foil having a thickness of 12 μm to a uniform thickness, and the drying process was carried out twice to apply both sides. Thereafter, roll pressing was performed to prepare a negative electrode. The coating amount of the obtained negative electrode was 210 g / m ^{2 on} both sides, and the bulk density of the active material was 1.5 g / cm ³ .

Subsequently, a separator made of a polyethylene microporous film having a thickness of about 55 mm and a length of 80 cm and having a thickness of 18 μm (porosity of 50%, pore diameter of 0.1 μm to 1 μm) was prepared as described above. Was wound in a roll shape with a diameter of about 17 mm. The wound coil is put into an iron cylindrical can having a diameter of about 18 mm and a length of 65 mm, and about 5 g of an electrolyte solution having a 1: 3 volume ratio of ethylene carbonate and ethylmethyl carbonate in which 1 mol / l of LiPF ₆ is dissolved. The cylindrical battery was manufactured by sealing.

(Rate characteristics evaluation)
The cylindrical battery obtained as described above was charged in a constant temperature bath at a constant temperature of 20 ° C. for 8 hours at a constant voltage of 4.2 V (positive electrode-negative electrode potential) with a constant current of 0.3 C in the first cycle. The battery was discharged to a potential of 3.0 V with a 3C constant current (product name: ACD-01, manufactured by Asuka Electronics Co., Ltd.). Here, “1.0 C” is a current value at which a fully charged battery can discharge electricity in one hour, and 1.0 C of this battery corresponds to 2000 mA. After the first charge / discharge, the battery was charged for 5 hours in a constant temperature and constant voltage system of 0.5C and 4.2V in a constant temperature bath at 20 ° C, and then discharged to 3V at 3.0C. At this time, the rate characteristic of 3C represented by the following formula was 80%. The results are shown in Table 2.
3C rate characteristic (%) = [(3C discharge amount) / (0.3C discharge amount)] × 100

(Cycle characteristic evaluation)
The cylindrical battery obtained as described above was charged in a constant temperature bath at a constant temperature of 20 ° C. for 8 hours at a constant voltage of 4.2 V (positive electrode-negative electrode potential) with a constant current of 0.3 C in the first cycle. The battery was discharged to a potential of 3.0 V with a 3C constant current (product name: ACD-01, manufactured by Asuka Electronics Co., Ltd.). After the first charge / discharge, after charging for 3 hours in a constant temperature constant voltage system of 1.0C and 4.2V in a constant temperature bath at 20 ° C, 300 cycles of discharging to 3.0V at 1.0C Repeated. At this time, the 300 cycle discharge amount retention rate (cycle characteristic) represented by the following formula was 90%. The results are shown in Table 2.
300 cycle discharge amount maintenance rate (%) = [(discharge amount at the 300th cycle) / (discharge amount at the second cycle)] × 100

[Example 2]
Instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L, iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 0.1 mol / L A positive electrode active material of Example 2 was obtained in the same manner as in Example 1, except that an aqueous solution of was used. The results of ICP analysis of the obtained positive electrode active material are shown in Table 1. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 2.

Example 3
Instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L, an aqueous solution of chromium nitrate nonahydrate (Cr (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L A positive electrode active material of Example 3 was obtained in the same manner as in Example 1 except that was used. Table 1 shows the results of ICP analysis of the Cr content of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 3.

Example 4
Except for using an aqueous solution of sodium silicate (Na ₂ SiO ₃ ) 0.1 mol / L instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L, The positive electrode active material of Example 4 was obtained by the same operation as in Example 1. Table 1 shows the results of ICP analysis of the Si content and Na content of the positive electrode active material obtained. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 4.

Example 5
Except for using an aqueous solution of potassium silicate (K ₂ SiO ₃ ) 0.1 mol / L instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L, The positive electrode active material of Example 5 was obtained by the same operation as in Example 1. Table 1 shows the results of ICP analysis of the Si content and the K content of the positive electrode active material obtained. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 5.

Example 6
Example 1 except that an aqueous solution of iron chloride (FeCl ₃ ) 1 mol / L was used instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ .9H ₂ O) 1 mol / L Thus, a positive electrode active material of Example 6 was obtained. Table 1 shows the results of ICP analysis of Fe amount and Cl amount of the positive electrode active material obtained. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 6.

Example 7
In place of an aqueous solution of iron nitrate (Fe ₂ (SO ₄ ) ₃ ) 1 mol / L instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ .9H ₂ O) 1 mol / L, 150 A positive electrode active material of Example 7 was obtained in the same manner as in Example 1, except that the powder was obtained by heating at a temperature of 1C for 1 hour and further heating at a temperature of 550C for 1 hour. Table 1 shows the results of ICP analysis of Fe amount and S amount of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 7.

Example 8
As a positive electrode active material, manganese hydroxide was immersed in an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ .9H ₂ O) 1 mol / L and heated in air at a temperature of 150 ° C. for 1 hour. Furthermore, it heated at the temperature of 350 degreeC for 1 hour, and obtained the powder. The obtained powder and lithium hydroxide were mixed, heated at a temperature of 900 ° C. for 8 hours, and then cooled to obtain LiMn ₂ O ₄ . Table 1 shows the results of ICP analysis of the amount of Fe of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 8.

Example 9
Instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L, an aqueous solution of potassium carbonate (K ₂ CO ₃ ) 1 mol / L was used, and the temperature was 150 ° C. in the atmosphere. The positive electrode active material of Example 8 was obtained in the same manner as in Example 8, except that the powder was obtained by heating at 700 ° C. for 1 hour and then heating at 700 ° C. for 1 hour. Table 1 shows the result of ICP analysis of the K amount of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 9.

Example 10
As a positive electrode active material, iron oxalate dihydrate (FeC ₂ O ₄ .2H ₂ O) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) are set to have a molar ratio of Fe to P of 1: 1. And then heated in air at a temperature of 150 ° C. for 1 hour while immersed in a 1 mol / L aqueous solution of chromium nitrate nonahydrate (Cr (NO ₃ ) ₂ · 9H ₂ O), and then at a temperature of 350 ° C. And heated for 1 hour to obtain a powder. The obtained powder and lithium carbonate (Li ₂ CO ₃ ) are mixed, heated in a nitrogen gas stream at a temperature of 500 ° C. for 1 hour, further heated at a temperature of 800 ° C. for 15 hours, and then cooled to obtain LiFePO ₄ . It was. Table 1 shows the results of ICP analysis of the Cr content of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 10. However, in Example 10, the charge voltage for rate characteristic evaluation and cycle characteristic evaluation was 3.8 V, and the discharge voltage was 2.5 V.

Example 11
Example 10 except that an aqueous solution of potassium carbonate (K ₂ CO ₃ ) 1 mol / L was used instead of an aqueous solution of chromium nitrate nonahydrate (Cr (NO ₃ ) ₂ .9H ₂ O) 1 mol / L The positive electrode active material of Example 11 was obtained by the same operation as in Example 11. Table 1 shows the result of ICP analysis of the K amount of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 11. However, in the case of Example 11, the charge voltage for rate characteristic evaluation and cycle characteristic evaluation was 3.8 V, and the discharge voltage was 2.5 V.

Example 12
In place of an aqueous solution of sodium nitrate (Na ₂ CO ₃ ) 1 mol / L instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L, a temperature of 150 ° C. in the atmosphere The positive electrode active material of Example 12 was obtained in the same manner as in Example 1 except that the powder was obtained by heating at 700 ° C. for 1 hour and then heating at 700 ° C. for 1 hour. Table 1 shows the results of ICP analysis of the amount of Na of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Example 12.

[Comparative Example 1]
As a positive electrode active material, nickel hydroxide, manganese hydroxide, and cobalt hydroxide were mixed so that the molar ratio of metal elements was 1: 1: 1, heated at a temperature of 800 ° C. for 8 hours, cooled, and Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ was synthesized. The synthesized powder was classified to obtain Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ having an average particle diameter of 15 μm. Table 1 shows the results of ICP analysis of the Si amount, Fe amount, Cr amount, Na amount, K amount, Cl amount, and S amount of the obtained Li (Ni _1/3 Mn _1/3 Co _1/3 ) O _2. Shown in Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Comparative Example 1.

[Comparative Example 2]
Instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L, iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1.5 mol / L A positive electrode active material of Comparative Example 2 was obtained in the same manner as in Example 1, except that an aqueous solution of was used. Table 1 shows the results of ICP analysis of the amount of Fe of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Comparative Example 2.

[Comparative Example 3]
Instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ · 9H ₂ O) 1 mol / L, chromium nitrate nonahydrate (Cr (NO ₃ ) ₂ · 9H ₂ O) 1.5 mol / L A positive electrode active material of Comparative Example 3 was obtained in the same manner as in Example 1 except that the aqueous solution was used. Table 1 shows the results of ICP analysis of the Cr content of the obtained positive electrode active material. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Comparative Example 3.

[Comparative Example 4]
Except for using an aqueous solution of sodium silicate (Na ₂ SiO ₃ ) 0.3 mol / L instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ .9H ₂ O) 1 mol / L, A positive electrode active material of Comparative Example 4 was obtained by the same operation as in Example 1. Table 1 shows the results of ICP analysis of the Si content and Na content of the positive electrode active material obtained. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Comparative Example 4.

[Comparative Example 5]
Except for using an aqueous solution of potassium silicate (K ₂ SiO ₃ ) 0.25 mol / L instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ .9H ₂ O) 1 mol / L, A positive electrode active material of Comparative Example 5 was obtained in the same manner as in Example 1. Table 1 shows the results of ICP analysis of the Si content and the K content of the positive electrode active material obtained. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Comparative Example 5.

[Comparative Example 6]
Example 1 except that an aqueous solution of iron chloride (FeCl ₃ ) 2 mol / L was used instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ .9H ₂ O) 1 mol / L As a result, the positive electrode active material of Comparative Example 6 was obtained. Table 1 shows the results of ICP analysis of Fe amount and Cl amount of the positive electrode active material obtained. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Comparative Example 6.

[Comparative Example 7]
Instead of an aqueous solution of iron nitrate nonahydrate (Fe (NO ₃ ) ₂ .9H ₂ O) of 1 mol / L, an aqueous solution of iron sulfate (Fe ₂ (SO ₄ ) ₃ ) of 2 mol / L is used. A positive electrode active material of Example 7 was obtained in the same manner as in Example 1, except that the powder was obtained by heating at a temperature of 1C for 1 hour and further heating at a temperature of 550C for 1 hour. Table 1 shows the results of ICP analysis of Fe amount and Cl amount of the positive electrode active material obtained. Table 2 shows the results of rate characteristic evaluation and cycle characteristic evaluation using the positive electrode active material of Comparative Example 7.

  From Table 2, it was shown that Examples 1-7 have rate characteristics and cycle characteristics superior to those of Comparative Examples 1-7.

  The positive electrode active material for nonaqueous electrolyte secondary batteries according to the present invention has industrial applicability as a positive electrode active material for nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries and lithium ion capacitors.

Claims (4)

Including at least one oxide selected from the group consisting of an oxide represented by the following formula (I) and an oxide represented by the formula (II),
Containing at least one element selected from the group consisting of Si, Fe, and Cr, in an amount of 10 ppm or more and 1000 ppm or less per element with respect to the mass of the positive electrode active material;
Positive electrode active material for non-aqueous electrolyte secondary battery.
(I) Li _{1 + x} MO ₂
(In formula (I), M represents one or more metal elements, and x satisfies −0.2 <x <0.3.)
(II) Li _{1 + x} Mn _2-y M ′ _y O ₄
(In formula (II), M ′ represents one or more metal elements other than Mn, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <2.) An oxide represented by the following formula (III):
Containing at least one element selected from the group consisting of Si and Cr, with respect to the mass of the positive electrode active material, of 10 ppm or more and 1000 ppm or less per element,
Positive electrode active material for non-aqueous electrolyte secondary battery.
(III) Li _{1 + x} Fe _1-y M ″ _y PO ₄
(In formula (III), M ″ represents one or more metal elements other than Fe, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <1.) Including at least one oxide selected from the group consisting of an oxide represented by the following formula (IV), an oxide represented by the formula (V), and an oxide represented by the formula (IV),
A positive electrode active material for a non-aqueous electrolyte secondary battery containing at least one element selected from the group consisting of Na, K, Cl, and S with respect to the positive electrode active material mass of 10 ppm or more and 2000 ppm or less per element .
(IV) Li _{1 + x} MO ₂
(In formula (IV), M represents one or more metal elements, and x satisfies −0.2 <x <0.3.)
(V) Li _{1 + x} Mn _2-y M ′ _y O ₄
(In Formula (V), M ′ represents one or more metal elements other than Mn, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <2.)
(IV) Li _{1 + x} Fe _1-y M ″ _y PO ₄
(In formula (IV), M ″ represents one or more metal elements other than Fe, and x and y satisfy −0.2 <x <0.3 and 0 ≦ y <1.)   The nonaqueous electrolyte secondary battery which has a positive electrode containing the positive electrode active material of any one of Claims 1-3.