JP2004235144A - Nonaqueous electrolyte secondary battery and negative electrode active substance therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode active substance for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery which have excellent battery characteristics even under more severe service environment. <P>SOLUTION: The negative electrode active substance for the nonaqueous electrolyte secondary battery comprises a lithium/transition metal complex oxide having a spinel structure containing an alkaline metal and/or an alkaline earth metal. The addition of the alkaline metal and/or the alkaline earth metal enables the diffusion resistance of lithium ions to decrease, and will improve the output characteristics. Further, it enables the crystalline structure of the lithium/transition metal complex oxide having the spinel structure to stabilize, and will improve the charge/discharge cycle characteristics. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery and a negative electrode active material for a non-aqueous electrolyte secondary battery (hereinafter, simply referred to as a “negative electrode active material”), which are suitably used for mobile phones, personal computers, electric vehicles, and the like. Also referred to as).

  Non-aqueous electrolyte secondary batteries are characterized by higher operating voltage and higher energy density than conventional nickel cadmium secondary batteries and the like, and are widely used as power supplies for electronic devices. As a negative electrode active material of this nonaqueous electrolyte secondary battery, a carbon material is mainly used because of a small amount of dendrite deposition on the negative electrode surface. Until now, sufficient battery characteristics have been obtained with a nonaqueous electrolyte secondary battery using a carbon material as the negative electrode active material.

  However, at present, mobile devices such as mobile phones, notebook computers, digital cameras, and the like have more severe usage environments due to higher functions such as being provided with various functions and use at high and low temperatures. It has become something. In addition, application to power sources such as batteries for electric vehicles is expected, and non-aqueous electrolyte secondary batteries using a carbon material as the negative electrode active material have not been able to provide sufficient battery characteristics. Is required.

When a carbon material is used as the negative electrode active material, a problem of retention (irreversible capacity) arises in that lithium ions are trapped in the carbon material in the first discharge and do not contribute to the subsequent battery reaction, resulting in a decrease in discharge capacity. Cause. Further, since the oxidation / reduction potential of the carbon material is as low as 0.1 V with respect to the potential of Li / Li ⁺ , the nonaqueous electrolyte is decomposed on the surface of the negative electrode active material, reacts with lithium, and a lithium compound is formed on the surface of the negative electrode active material. As charge / discharge is repeated for the reasons such as generation, lithium contributing to charge / discharge is deactivated, and cycle charge / discharge characteristics deteriorate. Further, dendrites deposited on the surface of the negative electrode may cause an internal short circuit, and cannot be said to have sufficient reliability and safety.

Patent Document 1, the general _{formula Li 4/3 Ti 5/3-x} Fe x O 4 , lithium titanate represented by (0 <x ≦ 0.2) which describes the use as a negative electrode active material I have. Then, it is estimated that by replacing a part of the titanium element with the iron element, the valence of the Ti element in the crystal is changed to improve the conductivity of the active material, and has a high energy density, and No precipitation reaction of lithium occurs, and safety and reliability are improved.
Patent Literature 2 discloses that a general formula Li _x Ti _{5 / 3-y} L _y O ₄ (L is one or more transition metals and elements other than Ti, 4/3 ≦ x ≦ 7/3, 0 ≦ It describes that an oxide fired body having a spinel structure represented by y ≦ 5/3) is used as a main component of the negative electrode active material. Further, it is described that a non-aqueous electrolyte lithium secondary battery having excellent storage characteristics can be obtained because the negative electrode active material hardly causes a side reaction with an electrolyte.

  However, these negative electrode active materials could not improve the cycle characteristics.

JP 2001-185141 A JP 2000-156229 A

  An object of the present invention is to provide a negative electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery having excellent battery characteristics even in a more severe use environment. That is, it is to provide a negative electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery having excellent cycle characteristics (cycle charge / discharge characteristics).

  The negative electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a negative electrode active material for a non-aqueous electrolyte secondary battery having a lithium transition metal composite oxide having a spinel structure containing an alkali metal and / or an alkaline earth metal. Is a substance.

  The transition metal of the lithium transition metal composite oxide is preferably composed of two or more kinds.

  Preferably, the lithium transition metal composite oxide contains aluminum.

  The lithium transition metal composite oxide preferably contains boron.

  The lithium transition metal composite oxide preferably contains at least one selected from the group consisting of fluorine, chlorine, bromine and iodine.

  The lithium transition metal composite oxide preferably contains sulfur.

The number of the lithium transition metal composite oxide is represented by the general formula _{Li a Ti b O 4 + c} (a is a number satisfying 0.8 ≦ a ≦ 1.5, b is satisfying 1.5 ≦ b ≦ 2.2 And c represents a number satisfying -0.5 ≦ c ≦ 0.5).

The lithium transition metal composite oxide is represented by the general formula _{Li a Ti b M d O 4} + c (2 Group wherein, M is one or more transition metals other than titanium, of the periodic table, Group 13 and Group 14 elements, halogen Represents at least one element selected from the group consisting of elements and sulfur, a + d represents a number satisfying 0.8 ≦ a + d ≦ 1.5, and b represents a number satisfying 1.5 ≦ b ≦ 2.2 , D represents a number satisfying 0 ≦ d ≦ 0.1, and c represents a number satisfying −0.5 ≦ c ≦ 0.5).

  It is preferable that the lithium transition metal composite oxide is a particle and has a sulfate group at least on the surface of the particle.

The lithium transition metal composite oxide used for the negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of the present invention may have Al ₂ O ₃ and / or LiTiO ₂ on at least a part of its surface. preferable.

  The non-aqueous electrolyte secondary battery according to the present invention uses the negative electrode active material for a non-aqueous electrolyte secondary battery according to any of the present invention.

  Non-aqueous electrolyte secondary battery described in the present invention is a non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte, for the non-aqueous electrolyte secondary battery according to any of the present invention The negative electrode active material is used as the negative electrode active material of the negative electrode.

The non-aqueous electrolyte secondary battery described in the present invention is a non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte. Used as a negative electrode active material.
I: formula _{Li 1 + e Mn 2-e} O 4 + f (e represents a number satisfying -0.2 ≦ e ≦ 0.2, f is a number satisfying -0.5 ≦ f ≦ 0.5.) ,
Li _g WO _h (W represents Co and / or Mn, g is a number satisfying 0.8 ≦ g ≦ 1.2, h is a number satisfying 1.8 ≦ h ≦ 2.2.) ,
_{Li i Ni j Co k X (} 1-j-k) O l (X is Al or Mn, i represents a number satisfying 0.95 ≦ i ≦ 1.10, j is 0.1 ≦ j ≦ 0. 9 represents a number that satisfies 9, 9 represents a number that satisfies 0.1 ≦ k ≦ 0.9, and 1 represents a number that satisfies 1.8 ≦ l ≦ 2.2.)
The number _{Li m Mn n Y 3-m} -n O 4 + o (Y is at least one selected from the group consisting of Co, Fe, Cu, Cr and Ni, m is satisfying 0.8 ≦ m ≦ 1.2 And n represents a number satisfying 0.5 ≦ n ≦ 1.5, and o represents a number satisfying −0.5 ≦ o ≦ 0.5.)
And Li _p Z _q PO _{4 + r} (Z represents Co and / or Fe, p represents a number satisfying 0.8 ≦ p ≦ 1.2, and q represents a number satisfying 0.9 ≦ q ≦ 1.1. And r represents a number satisfying −0.2 ≦ r ≦ 0.2.)
A positive electrode active material for a non-aqueous electrolyte secondary battery having at least one lithium transition metal composite oxide selected from the group consisting of:
II: The negative electrode active material for a non-aqueous electrolyte secondary battery according to any of the present invention.

  It is considered that by containing an alkali metal and / or an alkaline earth metal, the crystal structure of the lithium transition metal composite oxide having a spinel structure is stabilized, and thus the cycle characteristics are improved.

  It is considered that when two or more transition metals are contained, a part of the transition metal of the lithium transition metal composite oxide is always replaced with another transition metal, and the crystal structure is further stabilized and the cycle characteristics are improved.

It is considered that when aluminum is contained, a part of the transition metal of the lithium transition metal composite oxide is replaced by aluminum, whereby the crystal structure is further stabilized and the cycle characteristics are improved.
Further, it is considered that the compound containing aluminum covers the surface of the lithium transition metal particles and suppresses the reaction with the electrolytic solution. Therefore, thermal stability is improved.

It is considered that the inclusion of boron suppresses the reaction with the electrolyte and further improves the cycle characteristics.
In addition, it is considered that the boron-containing compound coats the particle surface of the lithium transition metal composite oxide to reduce the polarization action. Therefore, the insertion / desorption reaction of lithium into / from the particles is smoothly performed, and the load characteristics are improved.

It is considered that by containing at least one halogen element selected from the group consisting of fluorine, chlorine, bromine and iodine, the reaction with the electrolyte is suppressed and the cycle characteristics are further improved.
In addition, it is considered that the compound containing a halogen element covers the particle surface of the lithium transition metal composite oxide, and the polarization action is reduced. Therefore, the insertion / desorption reaction of lithium into / from the particles is smoothly performed, and the load characteristics are improved.

It is considered that by containing sulfur, the reaction with the electrolyte is suppressed, and the cycle characteristics are further improved.
Further, it is considered that the compound containing sulfur covers the surface of the lithium transition metal particles and suppresses the reaction with the electrolytic solution. Therefore, thermal stability is improved.
Further, it is considered that the compound containing sulfur covers the particle surface of the lithium transition metal composite oxide, and the polarization action is reduced. Therefore, the insertion / desorption reaction of lithium into / from the particles is smoothly performed, and the load characteristics are improved.

Formula _{Li a Ti b O 4 + c} (a is a number satisfying 0.8 ≦ a ≦ 1.5, b is a number satisfying 1.5 ≦ b ≦ 2.2, c is -0.5 ≦ The cycle characteristics, safety, and reliability are improved by using lithium titanate represented by the following formula: c ≦ 0.5.

In the general formula _{Li a Ti b M d O 4} + c ( wherein, M is selected from Group 2, Group 13 and Group 14 elements, the group consisting of halogen and sulfur one or more transition metals of the Periodic Table other than titanium A + d represents a number satisfying 0.8 ≦ a + d ≦ 1.5, b represents a number satisfying 1.5 ≦ b ≦ 2.2, and d represents 0 ≦ d ≦ 0. 1 represents a number that satisfies 1 and c represents a number that satisfies −0.5 ≦ c ≦ 0.5.) The cycle characteristics, safety, and reliability are improved by using lithium titanate represented by the formula:

  It is considered that the presence of the sulfate group on the surface of the lithium transition metal composite oxide particles facilitates the passage of electrons around the particles, and further improves the cycle characteristics.

It is considered that by using Al ₂ O ₃ as the coating layer, the mobility of lithium ions is increased, and the load characteristics and output characteristics are improved. It is considered that the use of LiTiO ₂ as the coating layer increases the mobility of lithium ions and improves load characteristics and output characteristics.

  By using the negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of the present invention as a negative electrode active material of a negative electrode, it is possible to obtain a non-aqueous electrolyte secondary battery excellent in cycle characteristics, safety and reliability. it can.

When the positive electrode active material is Li _{1 + e} Mn _2-e O _{4 + f} , the use of the negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention allows the non-aqueous electrolyte to have very excellent cycle characteristics, safety and reliability. The following battery can be obtained.
If the positive electrode active material is a mixture of _Li g CoO _h and _{Li 1 + e Mn 2-e} O 4 + f, the cycle characteristics by using a negative electrode active material for a nonaqueous electrolyte secondary battery according to the present invention, only the safety and reliability In addition, a non-aqueous electrolyte secondary battery having excellent load characteristics and output characteristics can be obtained.
If the positive electrode active material is _{Li i Ni j Co k X (} 1-j-k) O l, cycle characteristics by using a negative electrode active material for a nonaqueous electrolyte secondary battery according to the present invention, only the safety and reliability In addition, a nonaqueous electrolyte secondary battery having excellent discharge capacity, load characteristics, and output characteristics can be obtained.
If the positive electrode active material is _{Li m Mn n Y 3-m} -n O 4 + o, the cycle characteristics by using a negative electrode active material for a nonaqueous electrolyte secondary battery according to the present invention, not only the safety and reliability, high A non-aqueous electrolyte secondary battery with a potential can be obtained.
If the positive electrode active material is _{Li p Z q PO 4 + r} , the cycle characteristics by using a negative electrode active material for a nonaqueous electrolyte secondary battery according to the present invention, not only the safety and reliability, non-aqueous electrolyte of a high potential two The following battery can be obtained.

  Hereinafter, a negative electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery according to the present invention will be described with reference to embodiments, examples, and FIGS. However, the present invention is not limited to the embodiment, the examples, and FIGS.

The negative electrode active material of the present invention has a lithium transition metal composite oxide having a spinel structure. The “spinel structure” is one of typical crystal structure types observed in AB ₂ O ₄ type compounds (A and B are metal elements) as a double oxide.
FIG. 1 is a schematic diagram showing a crystal structure of a lithium transition metal composite oxide having a spinel structure. In FIG. 1, lithium atom 1 occupies the tetrahedral site of the 8a site, oxygen atom 2 occupies the 32e site, and transition metal atom 3 (and possibly excess lithium atom) is the octahedral site of 16d site 3. Occupy.

  Examples of the lithium transition metal composite oxide having a spinel structure include lithium titanate and lithium manganate. Preferred is lithium titanate.

  The alkali metal and / or alkaline earth metal is preferably at least one selected from the group consisting of lithium, sodium, potassium, magnesium and calcium. It is considered that when these elements enter the 16d site, the crystal structure is stabilized and the cycle charge / discharge characteristics are improved. More preferably, it is magnesium and / or calcium.

  In the present invention, the transition metal of the lithium transition metal composite oxide is preferably composed of two or more types. As the two or more transition metals, at least one selected from the group consisting of titanium, iron, cobalt, zirconium, manganese and nickel is preferable. More preferably, it is at least one selected from the group consisting of titanium, iron, zirconium and nickel.

  In the present invention, the combination of an alkali metal and / or an alkaline earth metal and two or more transition metals constituting the lithium transition metal composite oxide includes magnesium and iron and titanium, magnesium and cobalt and titanium, magnesium and zirconium. Preferable examples include titanium, magnesium and manganese and titanium, magnesium and nickel and titanium, calcium and iron and titanium, calcium and cobalt and titanium, calcium and zirconium and titanium, calcium and manganese and titanium, and calcium and nickel and titanium.

  In the present invention, the alkali metal and / or alkaline earth metal constituting the lithium transition metal composite oxide, the combination of two or more transition metals and aluminum include magnesium, iron and titanium, aluminum, magnesium, cobalt and titanium. Aluminum, magnesium and zirconium and titanium and aluminum, magnesium and manganese and titanium and aluminum, magnesium and nickel and titanium and aluminum, calcium and iron and titanium and aluminum, calcium and cobalt and titanium and aluminum, calcium and zirconium and titanium and aluminum, Preferable examples include calcium, manganese, titanium, and aluminum, and calcium, nickel, titanium, and aluminum.

  In the present invention, the alkali metal and / or alkaline earth metal constituting the lithium transition metal composite oxide, the combination of two or more transition metals and boron include magnesium, iron, titanium, and boron, magnesium, cobalt, and titanium. Boron, magnesium, zirconium, titanium, boron, magnesium, manganese, titanium, boron, magnesium, nickel, titanium, boron, calcium, iron, titanium, boron, calcium, cobalt, titanium, boron, calcium, zirconium, titanium, boron, Preferable examples include calcium, manganese, titanium, and boron, and calcium, nickel, titanium, and boron.

In the present invention, the lithium transition metal composite oxide preferably has boron at least on the surface of the particle. By having boron on the surface of the particles, the reaction with the electrolyte can be further suppressed, and the cycle characteristics are improved. In the present invention, the effects of the present invention are exhibited regardless of the form of boron present on the surface of the particles of the lithium transition metal composite oxide.
For example, even when boron is coated on the entire surface of the particles of the lithium transition metal composite oxide, boron is coated on a part of the surface of the particles of the lithium transition metal composite oxide. Even so, cycle characteristics and load characteristics are improved. Further, boron only needs to be present at least on the surface of the particles. Therefore, some of the boron may be present inside the particles.

  Whether boron is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, analysis can be performed by Auger Electron Spectroscopy (AES) or X-ray Photoelectron Spectroscopy (XPS).

  In the present invention, the lithium transition metal composite oxide preferably further contains at least one selected from the group consisting of fluorine, chlorine, bromine and iodine. As at least one selected from fluorine, chlorine, bromine and iodine, at least one selected from the group consisting of fluorine, chlorine and iodine is preferable. More preferably, it is fluorine.

  In the present invention, the alkali metal and / or alkaline earth metal constituting the lithium transition metal composite oxide, two or more transition metals, and at least one combination selected from the group consisting of fluorine, chlorine, bromine and iodine are as follows. Magnesium, iron, titanium, fluorine, magnesium, cobalt, titanium, fluorine, magnesium, zirconium, titanium, fluorine, magnesium, manganese, titanium, fluorine, magnesium, nickel, titanium, fluorine, calcium, iron, titanium, fluorine, calcium And cobalt and titanium and fluorine, calcium and zirconium and titanium and fluorine, calcium and manganese and titanium and fluorine, and calcium and nickel and titanium and fluorine.

  In the present invention, the lithium transition metal composite oxide preferably has at least one selected from the group consisting of fluorine, chlorine, bromine and iodine on at least the surface of the particles. By having at least one selected from the group consisting of fluorine, chlorine, bromine and iodine on the surface of the particles, the reaction with the electrolyte can be further suppressed and the cycle characteristics are improved. In the present invention, at least one selected from the group consisting of fluorine, chlorine, bromine, and iodine exerts the effects of the present invention regardless of the form present on the surface of the lithium transition metal composite oxide particles. For example, even when at least one selected from the group consisting of fluorine, chlorine, bromine and iodine is coated on the entire surface of the particles of the lithium transition metal composite oxide, fluorine, chlorine, bromine and iodine Even when at least one selected from the group is coated on a part of the surface of the lithium transition metal composite oxide particles, the cycle characteristics and the load characteristics are improved. At least one selected from the group consisting of fluorine, chlorine, bromine and iodine may be present at least on the surface of the particles. Therefore, at least one part selected from the group consisting of fluorine, chlorine, bromine and iodine may be present inside the particles.

  Whether or not at least one selected from the group consisting of fluorine, chlorine, bromine and iodine is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, it can be analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).

  In the present invention, the alkali metal and / or alkaline earth metal constituting the lithium transition metal composite oxide, the combination of two or more transition metals and sulfur include magnesium, iron, titanium, and sulfur, magnesium, cobalt, and titanium. Sulfur, magnesium and zirconium and titanium and sulfur, magnesium and manganese and titanium and sulfur, magnesium and nickel and titanium and sulfur, calcium and iron and titanium and sulfur, calcium and cobalt and titanium and sulfur, calcium and zirconium and titanium and sulfur, Preferable examples include calcium, manganese, titanium, and sulfur, and calcium, nickel, titanium, and sulfur.

  In the present invention, as a combination of elements constituting the lithium transition metal composite oxide, magnesium, iron, titanium, sulfur and aluminum, magnesium and iron and titanium and sulfur and boron, magnesium and iron and titanium and sulfur and fluorine, magnesium And cobalt and titanium and sulfur and aluminum; magnesium and cobalt and titanium and sulfur and boron; magnesium and cobalt and titanium and sulfur and fluorine; magnesium and zirconium and titanium and sulfur and aluminum; magnesium and zirconium and titanium and sulfur and boron and magnesium. And zirconium and titanium and sulfur and fluorine, magnesium and manganese and titanium and sulfur and aluminum, magnesium and manganese and titanium and sulfur and boron, magnesium and manganese and titanium and sulfur and fluorine, magnesium and nickel Metal, titanium, sulfur, aluminum, magnesium, nickel, titanium, sulfur, boron, magnesium, nickel, titanium, sulfur, fluorine, calcium, iron, titanium, sulfur, aluminum, calcium, iron, titanium, sulfur, boron, calcium, Iron and titanium and sulfur and sulfur, calcium and cobalt and titanium and sulfur and aluminum, calcium and cobalt and titanium and sulfur and boron, calcium and cobalt and titanium and sulfur and fluorine, calcium and zirconium and titanium and sulfur and aluminum, calcium and Zirconium and titanium and sulfur and boron, calcium and zirconium and titanium and sulfur and fluorine, calcium and manganese and titanium and sulfur and aluminum, calcium and manganese and titanium and sulfur and boron, calcium and manganese and titanium and sulfur and fluorine. , Calcium and nickel, titanium and sulfur and aluminum, calcium and nickel, titanium, sulfur and boron, calcium, nickel, and titanium and sulfur and fluorine are preferably exemplified.

In the present invention, a lithium transition metal composite oxide is represented by the general formula _{Li a Ti b O 4 + c} (a is a number satisfying 0.8 ≦ a ≦ 1.5, b is a 1.5 ≦ b ≦ 2.2 Represents a number that satisfies, and c represents a number that satisfies −0.5 ≦ c ≦ 0.5.)
a is preferably 1.0 or more, and more preferably 1.4 or less. b is preferably 1.6 or more, and more preferably 2.0 or less.

In the present invention, the lithium transition metal composite oxide is a compound represented by the general formula Li _x Ti _y M _z O _{4 + w} (wherein M is one or more transition metals other than titanium, and a group 2 or 13 or 14 group of the periodic table). Represents at least one selected from the group consisting of an element and a halogen element, x + z represents a number satisfying 0.8 ≦ x + z ≦ 1.5, y represents a number satisfying 1.5 ≦ y ≦ 2.2, z represents a number satisfying 0 <z ≦ 0.1, and w represents a number satisfying −0.5 ≦ w ≦ 0.5).
x + z is preferably 1.0 or more, and more preferably 1.4 or less. y is preferably 1.6 or more, and more preferably 2.0 or less.

  In the present invention, the lithium transition metal composite oxide exists in the form of particles. Specifically, the lithium transition metal composite oxide exists in the form of particles composed of one or both of primary particles and secondary particles that are aggregates thereof. That is, the lithium transition metal composite oxide exists in the form of particles, and the particles may be composed of only primary particles, or may be composed of only secondary particles that are aggregates of primary particles. It may be composed of both particles and secondary particles.

  In the present invention, the lithium transition metal composite oxide preferably has a sulfate group at least on the surface of the particle. In the present invention, the effect of the present invention is exhibited regardless of the form of the sulfate group on the surface of the particles of the lithium transition metal composite oxide. For example, even when the sulfate is coated on the entire surface of the particles of the lithium transition metal composite oxide, when the sulfate is coated on a part of the surface of the particles of the lithium transition metal composite oxide. However, the cycle characteristics are further improved. Further, the sulfate group may be present at least on the surface of the particles. Therefore, some of the sulfate groups may be present inside the particles.

  Whether or not sulfate is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, it can be analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).

The sulfate group used in the present invention is preferably based on at least one selected from the group consisting of alkali metal sulfate, alkaline earth metal sulfate, transition metal sulfate and organic compound sulfate.
In particular, it is preferably based on at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferably based on alkali metal sulfates. This is because these are chemically stable because they consist of a strong acid-strong base bond.
Specifically, examples of the inorganic salt include iron sulfate, cobalt sulfate, nickel sulfate, zinc sulfate, copper sulfate, lithium sulfate, and potassium sulfate. Among them, lithium sulfate, sodium sulfate, magnesium sulfate and calcium sulfate are preferred, and lithium sulfate and sodium sulfate are more preferred.
Examples of the organic salt include tetrabutylammonium hydrogen sulfate, trifluoromethanesulfonic acid, 1-naphthylamine-2-sulfonic acid, and 6-disulfonic acid.
These sulfates may be anhydrous or hydrated.

In the present invention, the lithium transition metal composite oxide used for the negative electrode active material for a non-aqueous electrolyte secondary battery preferably has Al ₂ O ₃ and / or LiTiO ₂ on at least a part of its surface. Al ₂ O ₃ and / or LiTiO ₂ exert the effects of the present invention regardless of the form of the particles on the surface of the lithium transition metal composite oxide particles. For example, even when Al ₂ O ₃ and / or LiTiO ₂ is coated on the entire surface of the particles of the lithium transition metal composite oxide, the Al ₂ O ₃ and / or LiTiO ₂ are converted to the lithium transition metal composite oxide. The cycle charge / discharge characteristics, storage characteristics, and safety are improved even when a part of the particles of the substance are coated. Further, Al ₂ O ₃ and / or LiTiO ₂ may be present at least on the surface of the particles. Therefore, part of Al ₂ O ₃ and / or LiTiO ₂ may be present inside the powder body.

Whether Al ₂ O ₃ and / or LiTiO ₂ is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, it can be analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).

Al ₂ O ₃ is not particularly limited, and examples thereof include aluminum oxide, low-temperature alumina, and high-temperature alumina.
The LiTiO ₂ is not particularly limited, and includes LiTiO ₂ belonging to the space group Fm3m, layered LiTiO _{2, and the} like. Among them, LiTiO ₂ belonging to the space group Fm3m is preferable. Among various lithium titanates, when LiTiO ₂ belonging to the space group Fm3m is used, an effect of improving load characteristics is realized.

The size of Al ₂ O ₃ is not particularly limited, but the center particle diameter is preferably 0.3 μm or less, more preferably 0.1 μm or less. If the size is too large, the coated portion becomes uneven and the effect cannot be exhibited.
The size of LiTiO ₂ is not particularly limited, but the central particle diameter is preferably 3 μm or less, more preferably 1 μm or less. This is because a lithium transition metal composite oxide can be easily coated in this range, and a discharge capacity lowers if it is too large. The shape of Al ₂ O ₃ and / or LiTiO ₂ is not limited to the spherical shape of the powder.

The method for producing Al ₂ O ₃ is not particularly limited, but for example, a Bayer method can be used. Bauxite is used as a raw material, crushed and treated with a hot solution of sodium hydroxide to elute sodium aluminate. The sodium aluminate solution is diluted appropriately, and the cast of gibbsite is added at an appropriate temperature and stirred to precipitate gibbsite. After filtration, washing and drying, the Gibbs stone is calcined in a rotary kiln to obtain Al ₂ O ₃ .

The method for producing LiTiO ₂ is not particularly limited. For example, when Li ₂ CO ₃ and TiO ₂ are used as raw materials and they are mixed and fired in a slight reducing atmosphere, Ti is present in a trivalent state. And LiTiO ₂ can be obtained.

The method for coating the powder main body with Al ₂ O ₃ and / or LiTiO ₂ is not particularly limited, and a commonly used mixer can be used. Among them, a high-speed flow mixer with high speed and high shearing property is preferable for adding a small amount.

  Although the production method of the negative electrode active material of the present invention is not particularly limited, it can be produced, for example, as in the following (1) and (2).

(1) Preparation of Raw Material Mixture Compounds described below are mixed so that each constituent element has a predetermined composition ratio, to obtain a raw material mixture. The compound used in the raw material mixture is selected according to the elements constituting the desired composition.
The method of mixing is not particularly limited. For example, a method in which a powdery compound is directly mixed to form a raw material mixture; mixed in a slurry using water and / or an organic solvent, and then dried to obtain a raw material mixture. Method: a method in which an aqueous solution of the above-described compound is mixed and precipitated, and the obtained precipitate is dried to form a raw material mixture;

Hereinafter, the compounds used in the raw material mixture will be exemplified.
Although the lithium compound is not particularly limited, for example, Li ₂ CO ₃ , LiOH, LiOH.H ₂ O, Li ₂ O, LiCl, LiNO ₃ , Li ₂ SO ₄ , LiHCO ₃ , Li (CH ₃ COO), fluoride Lithium, lithium bromide, lithium iodide, and lithium peroxide. Among them, Li ₂ CO ₃ , LiOH, LiOH · H ₂ O, Li ₂ O, LiNO ₃ , LiHCO ₃ , and Li (CH ₃ COO) are preferable.

Although the titanium compound is not particularly limited, for example, TiO, TiO ₂ , Ti ₂ O ₃ , TiCl ₂ , Ti (SO ₄ ) ₂ , titanium fluoride, titanium chloride, titanium bromide, titanium iodide, titanium oxide, sulfide Titanium and titanium sulfate are exemplified. Among them, TiO, TiO ₂ , Ti ₂ O ₃ , TiCl ₂ , and Ti (SO ₄ ) ₂ are preferable.

Although the magnesium compound is not particularly limited, for example, MgO, MgCO ₃ , Mg (OH) ₂ , MgCl ₂ , MgSO ₄ , Mg (NO ₃ ) ₂ , Mg (CH ₃ COO) ₂ , magnesium fluoride, magnesium chloride, odor Magnesium oxide, magnesium oxide, magnesium hydroxide, magnesium carbonate, and magnesium hydroxide. Among them, MgO, MgCO ₃ , Mg (OH) ₂ , MgCl ₂ , MgSO ₄ , Mg (NO ₃ ) ₂ , and Mg (CH ₃ COO) ₂ are preferable.

The zirconium compound is not particularly limited, for _{example, ZrF 2, ZrCl, ZrCl 2} , ZrBr 2, ZrI 2, ZrO, ZrO 2, ZrS 2, Zr (OH) 3, zirconium fluoride, zirconium chloride, zirconium bromide , Zirconium iodide, zirconium oxide, zirconium sulfide, and zirconium carbonate. Among them, ZrF ₂ , ZrCl, ZrCl ₂ , ZrBr ₂ , ZrI ₂ , ZrO, ZrO ₂ , ZrS ₂ , and Zr (OH) ₃ are preferable.

The aluminum compound is not particularly limited, but for example, Al ₂ O ₃ , Al (NO ₃ ) ₃ , Al ₂ (SO ₄ ) ₃ , Al ₂ (CO ₃ ) ₃ , Al (CH ₃ COO) ₃ , fluoride Examples include aluminum, aluminum chloride, aluminum oxide, aluminum hydroxide, aluminate, aluminum carbonate, and aluminum silicate. Among them, Al ₂ O ₃ , Al (NO ₃ ) ₃ , Al ₂ (SO ₄ ) ₃ , Al ₂ (CO ₃ ) ₃ , and Al (CH ₃ COO) ₃ are preferable.

The boron compound is not particularly limited, for _{example, B 2 O 3, H 3} BO 3, LiBO 2, borides, boron oxide, boron phosphate, and lithium borate. Among them, B ₂ O ₃ , H ₃ BO ₃ , and LiBO ₂ are preferable.

The compound containing a halogen element is not particularly limited, but for example, NH ₄ F, NH ₄ Cl, NH ₄ Br, NH ₄ I, LiF, LiCl, LiBr, LiI, MnF ₂ , MnCl ₂ , MnBr ₂ , MnI ₂ , Examples include hydrogen fluoride, oxygen fluoride, hydrofluoric acid, hydrogen chloride, hydrochloric acid, chlorine oxide, chlorine fluoride oxide, bromine oxide, bromine fluorosulfate, hydrogen iodide, iodine oxide, and periodic acid. Among them, NH ₄ F, NH ₄ Cl, NH ₄ Br, NH ₄ I, LiF, LiCl, LiBr, LiI, MnF ₂ , MnCl ₂ , MnBr ₂ , and MnI ₂ are preferable.

Although the sulfur-containing compound is not particularly limited, for example, Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , MgSO ₄ , sulfide, sulfur iodide, hydrogen sulfide, and sulfuric acid And salts thereof and nitrogen sulfide. Among them, Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , and MgSO ₄ are preferable.
Further, a compound containing two or more of the above-described elements may be used.

(2) Firing and grinding the raw material mixture Next, the raw material mixture is fired. The firing temperature, time, atmosphere, and the like are not particularly limited, and can be appropriately determined depending on the purpose.
The firing temperature is preferably at least 650 ° C, more preferably at least 750 ° C. If the firing temperature is too low, unreacted raw materials remain in the negative electrode active material, and the original characteristics of the negative electrode active material may not be utilized. Further, the firing temperature is preferably 960 ° C or lower, more preferably 940 ° C or lower. If the firing temperature is too high, it is not preferable because phase transition occurs and ramsteride-type Li ₂ Ti ₃ O ₇ or the like is generated. This causes a decrease in discharge capacity per unit weight, a decrease in cycle characteristics, and a decrease in operating voltage.
Generally, the firing time is preferably from 1 to 24 hours, and more preferably from 6 to 12 hours. If the firing time is too short, the diffusion reaction between the raw material particles does not proceed. If the firing time is too long, coarse particles are formed by sintering, which is not preferable.

  The firing atmosphere includes, for example, air, oxygen gas, a mixed gas thereof with an inert gas such as nitrogen gas and argon gas, an atmosphere in which the oxygen concentration (oxygen partial pressure) is controlled, and a weakly oxidizing atmosphere.

  After firing, if desired, the powder can be pulverized using a mortar, ball mill, vibration mill, pin mill, jet mill, or the like to obtain a powder having a desired particle size.

  Hereinafter, a preferred method for obtaining the negative electrode active material will be specifically described.

A lithium compound, a titanium compound, and a magnesium compound are mixed so that each constituent element has a predetermined composition ratio.
Next, the raw material mixture is fired in air or a weakly oxidizing atmosphere at a temperature of 810 ° C. for 12 hours to synthesize a lithium transition metal composite oxide according to the present invention.
A predetermined amount of sulfate is added to the obtained fired product. According to this method, a sulfate group can be easily present on the surface of the particle. A commercially available mixer can be used for the addition of sulfate.
Alternatively, a predetermined amount of sulfate may be added at the time of mixing the raw materials, and then the raw material mixture containing the sulfate may be fired.
By using the above production method, the non-aqueous electrolyte having a sulfate group of 0.03 mol% with respect to the lithium transition metal composite oxide on the surface of the particles of Li _1.28 Ti _1.7 Mg _0.02 O ₄ is obtained. A negative electrode active material for a secondary battery can be obtained.

  The negative electrode active material of the present invention can be obtained by the above-described manufacturing method.

The negative electrode active material of the present invention is suitably used for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery and a lithium ion polymer secondary battery.
That is, the nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery using the negative electrode active material of the present invention. The nonaqueous electrolyte secondary battery of the present invention may use the negative electrode active material of the present invention as at least a part of the negative electrode active material.

A preferred method for producing the negative electrode used in the nonaqueous electrolyte secondary battery of the present invention will be described below.
The negative electrode used in the non-aqueous electrolyte secondary battery of the present invention is obtained by mixing a powder of the negative electrode active material of the present invention, a conductive agent, a binder and a dispersant to form a slurry, and forming the slurry into a copper foil or the like. Of the negative electrode active material layer formed on the current collector.
FIG. 2 is a schematic sectional view of the negative electrode. As shown in FIG. 2, the negative electrode 13 has the negative electrode active material 5 held on the current collector 12 by the binder 4.

  Examples of the conductive agent used for the negative electrode plate include graphites such as natural graphite, flaky graphite, artificial graphite, and expanded graphite; carbon blacks such as acetylene black and Ketjen black; conductive fibers such as carbon fibers. Can be used alone or as a mixture thereof.

Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyamide, and acrylic resin.
Among them, polyvinylidene fluoride is preferable. The negative electrode active material of the present invention is easily compatible with polyvinylidene fluoride and has excellent slurry properties. Therefore, when polyvinylidene fluoride is used as a binder, cycle characteristics are further improved.
Note that a binder in a solvent may be used instead of the binder and the dispersant.

Since the negative electrode active material of the present invention has good miscibility with the conductive agent, the non-aqueous electrolyte secondary battery of the present invention is considered to have low internal resistance of the battery. This is considered to improve cycle characteristics and load characteristics, particularly load characteristics.
Further, the negative electrode active material of the present invention also has excellent slurry properties when mixed with a binder. Furthermore, when the negative electrode active material of the present invention does not contain coarse particles, the surface of the coating surface of the obtained negative electrode has excellent smoothness. For this reason, lithium ions enter and exit uniformly on the surface of the coating film surface due to charge and discharge, so that the cycle characteristics are extremely excellent.

  The nonaqueous electrolyte secondary battery of the present invention may use the negative electrode active material of the present invention as a negative electrode active material in a conventionally known nonaqueous electrolyte secondary battery, and other configurations are not particularly limited.

As the positive electrode active material, lithium cobaltate, lithium manganate, lithium nickelate, lithium cobalt manganate, lithium nickel manganate, nickel cobalt lithium aluminate, nickel cobalt lithium manganate and the like can be used. The general formula is represented as I above. LiCoO ₂ for lithium cobaltate, LiMn ₂ O ₄ for lithium manganate, LiNiO ₂ for lithium nickelate, LiCoMnO _{4 for} lithium cobalt manganate, Li ₂ NiMn ₃ O _{8 for} lithium nickel manganate, nickel cobalt Examples of the lithium aluminate include LiNi _0.65 Co _0.2 Al _0.15 O ₂ , and examples of the lithium nickel cobalt manganate include LiNi _1/3 Co _1/3 Mn _1/3 O ₂ .

  The positive electrode active material is preferably a positive electrode active material for a nonaqueous electrolyte secondary battery having at least a lithium transition metal composite oxide (hereinafter, also simply referred to as “positive electrode active material”). Preferred embodiments of the lithium transition metal composite oxide include the following (i) to (v).

(I) a lithium transition metal composite oxide represented by the general formula _{^{Li v Co 1-x M 1}} w M 2 x O y S z (M 1 represents Al or Ti, ^{M 2} represents Mg and / or Ba, v is a number satisfying 0.95 ≦ v ≦ 1.05, w is 0 or 0 <w ≦ 0.10 when M ¹ is Al, and 0 <w ≦ 0 when M ¹ is Ti. X represents a number satisfying 0 <x ≦ 0.10, y represents a number satisfying 1 ≦ y ≦ 2.5, and z represents a number satisfying 0 <z ≦ 0.015. Represents an aspect.).

  By combining the positive electrode active material having the lithium transition metal composite oxide with the negative electrode active material of the present invention, cycle characteristics can be further improved, and gas generation of the battery can be reduced.

At least (ii) the lithium-transition metal composite oxide represented by the general formula _{Li a Co 1-b M b} O c X d S e (M is Ti, Al, V, Zr, Mg, selected from the group consisting of Ca and Sr Represents one kind, X represents at least one kind selected from halogen elements, a represents a number satisfying 0.95 ≦ a ≦ 1.05, b represents a number satisfying 0 <b ≦ 0.10, c represents a number satisfying 1 ≦ c ≦ 2.5, d represents a number satisfying 0 <d ≦ 0.1, and e represents a number satisfying 0 <e ≦ 0.015.) Aspects.

  By combining the positive electrode active material having the lithium transition metal composite oxide with the negative electrode active material of the present invention, cycle characteristics can be further improved, and gas generation of the battery can be reduced.

  (Iii) the lithium transition metal composite oxide is at least one member selected from the group consisting of lithium cobaltate, lithium nickel cobaltate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate; The embodiment in which the proportion of zirconium present on the surface of is 20% or more.

  By combining the positive electrode active material having the lithium transition metal composite oxide with the negative electrode active material of the present invention, cycle characteristics can be further improved, and load characteristics and low-temperature characteristics can be improved.

In the positive electrode active material, the proportion of zirconium on the surface of the particles is 20% or more. The details will be described below.
In the present invention, “the existing ratio of zirconium on the surface of the lithium transition metal composite oxide particles” is determined as follows.
First, the presence of zirconium on the surface of particles of a lithium transition metal composite oxide is observed by an electron beam microanalyzer (EPMA) equipped with a wavelength dispersive X-ray spectrometer (WDX). Then, in the observation visual field, a portion having the largest zirconium amount per unit area (a portion having a large zirconium peak) is selected, and line analysis is performed along a line segment passing through this portion (for example, a line segment having a length of 300 μm). I do. In the line analysis, the quotient obtained by dividing the sum of the lengths of the portions where the peak was 4% or more when the value of the peak in the portion having the largest amount of zirconium per unit area as 100% was divided by the length of the line segment. Is defined as “the abundance ratio of zirconium on the surface of the lithium transition metal composite oxide particles”. In addition, it is preferable to use the average value of “the presence ratio of zirconium on the surface of the lithium transition metal composite oxide particles” by performing the line analysis a plurality of times (for example, 10 times).
In the above method, a portion where the peak of zirconium is less than 4% has a large difference from a portion where the amount of zirconium is the largest, and is regarded as a portion where zirconium does not exist.

  The above-mentioned “amount of zirconium present on the surface of the lithium transition metal composite oxide particles” indicates whether zirconium is present uniformly or unevenly on the surface of the lithium transition metal composite oxide particles. be able to.

  (Iv) An embodiment in which the lithium transition metal composite oxide is spinel-structured lithium manganate and contains aluminum and / or magnesium, and titanium and / or zirconium.

  By combining the positive electrode active material having the lithium transition metal composite oxide with the negative electrode active material of the present invention, cycle characteristics can be further improved, and gas generation of the battery can be reduced.

  (V) An embodiment in which the lithium transition metal composite oxide is spinel-structured lithium manganate, is a particle, and has a magnesium content of 20% or more on the surface of the particle.

  By combining the positive electrode active material having the lithium transition metal composite oxide with the negative electrode active material of the present invention, the cycle characteristics can be further improved, and the storage characteristics can be improved.

In the positive electrode active material, the proportion of magnesium on the surface of the particles is 20% or more. The details will be described below.
In the present invention, the “magnesium content on the surface of the lithium transition metal composite oxide particles” is determined as follows.
First, the presence state of magnesium on the surface of particles of a lithium transition metal composite oxide is observed using an electron beam microanalyzer (EPMA) equipped with a wavelength dispersive X-ray spectrometer (WDX). Then, in the observation visual field, a portion having the largest amount of magnesium per unit area (a portion having a large magnesium peak) is selected, and line analysis is performed along a line segment (for example, a line segment having a length of 300 μm) passing through this portion. I do. In the line analysis, the quotient obtained by dividing the total length of the portion where the peak was 4% or more when the value of the peak in the portion having the largest amount of magnesium per unit area as 100% was divided by the length of the line segment. Is defined as “the ratio of magnesium present on the surface of the lithium transition metal composite oxide particles”. Note that it is preferable to use the average value of “the ratio of magnesium present on the surface of the lithium transition metal composite oxide particles” by performing the line analysis a plurality of times (for example, 10 times).
In the above method, a portion where the peak of magnesium is less than 4% has a large difference from a portion where the amount of magnesium is the largest, and thus is regarded as a portion where magnesium does not exist.

  The above-mentioned “magnesium abundance ratio on the surface of the lithium transition metal composite oxide particles” indicates whether magnesium is uniformly present or unevenly present on the surface of the lithium transition metal composite oxide particles. be able to.

The positive electrode using the positive electrode active material containing the lithium transition metal composite oxide of I as a main component is preferably produced as follows.
The powder of the lithium transition metal composite oxide of the above I, a conductive agent, a binder and a dispersant are mixed to form a slurry, and the slurry is applied to a current collector such as an aluminum foil or supported. And press-rolling to form a positive electrode active material layer on the current collector.

The electrolyte is not particularly limited as long as it is a compound that does not deteriorate or decompose at the operating voltage.
Examples of the solvent include organic solvents such as dimethoxyethane, diethoxyethane, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, γ-butyrolactone, 2-methyltetrahydrofuran, dimethyl sulfoxide, and sulfolane. Is mentioned. These can be used alone or in combination of two or more.
Among them, ethylene carbonate and propylene carbonate are preferable as the high boiling point solvent, and dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferable as the low boiling point solvent. Particularly, a combination of ethylene carbonate and at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate is preferred. In this case, the weight ratio is preferably (ethylene carbonate) / (at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate) = 20/80 to 40/60.

Examples of the electrolyte include lithium salts such as lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium trifluoromethane.
Among them, lithium hexafluorophosphate is preferable.

In the negative electrode active material of the present invention, the decomposition of the electrolyte is suppressed, and as a result, the cycle characteristics are excellent.
When the nonaqueous electrolyte secondary battery of the present invention uses a mixture of ethylene carbonate and dimethyl carbonate as a solvent, and an electrolyte using lithium hexafluorophosphate as an electrolyte, it has excellent load characteristics and storage characteristics. Become.

  The above-mentioned solvent and electrolyte are mixed to form an electrolyte. Here, a gelling agent or the like may be added and used as a gel. Further, it may be used after being absorbed by a hygroscopic polymer. Further, a solid electrolyte having inorganic or organic lithium ion conductivity may be used.

  Examples of the separator include a porous film made of polyethylene or polypropylene. Among them, a porous film made of polyethylene is preferable.

If necessary, a non-aqueous electrolyte secondary battery is formed using components such as terminals and insulating plates.
The nonaqueous electrolyte secondary battery of the present invention can be obtained according to a standard method using the negative electrode active material of the present invention, the above-described negative electrode active material, electrolyte, separator and binder. Thereby, excellent battery characteristics that could not be achieved conventionally are realized.

As a preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, a band-shaped negative electrode constituted by forming a negative electrode active material layer using the negative electrode active material of the present invention as a negative electrode active material on both surfaces of a band-shaped negative electrode current collector, respectively. And a band-shaped positive electrode formed by forming a positive electrode active material layer using the positive electrode active material of I as a positive electrode active material on both surfaces of a band-shaped positive electrode current collector, and a band-shaped separator, and the band-shaped negative electrode, The band-shaped positive electrode is wound a plurality of times in a stacked state with the band-shaped separator interposed therebetween to form a spiral wound body in which the band-shaped separator is interposed between the band-shaped negative electrode and the band-shaped positive electrode. Non-aqueous electrolyte secondary batteries.
Such a non-aqueous electrolyte secondary battery has a simple manufacturing process and is less likely to crack the negative electrode active material layer and the positive electrode active material layer and to be separated from the strip separator. Also, the battery capacity is large and the energy density is high.

The shape of the nonaqueous electrolyte secondary battery may be a cylindrical shape, a coin shape, a square shape, or the like.
FIG. 3 is a schematic sectional view of a cylindrical battery. As shown in FIG. 3, in the cylindrical battery 20, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12 and the negative electrode 11 in which the negative electrode active material layer is formed on the current collector 12 Are repeatedly laminated via the separator 14.
FIG. 4 is a schematic partial cross-sectional view of the coin-type battery. As shown in FIG. 4, in the coin-type battery 30, a positive electrode 13 in which a positive electrode active material layer is formed on a current collector 12 and a negative electrode 11 are stacked via a separator 14.
FIG. 5 is a schematic perspective view of a prismatic battery. As shown in FIG. 5, in the prismatic battery 40, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12, and the negative electrode 11 in which the negative electrode active material layer is formed on the current collector 12 Are repeatedly laminated via the separator 14.

The use of the nonaqueous electrolyte secondary battery using the negative electrode active material of the present invention is not particularly limited. For example, notebook PC, pen input PC, pocket PC, notebook type word processor, pocket word processor, e-book player, mobile phone, cordless phone handset, electronic notebook, calculator, LCD TV, electric shaver, electric tool, electronic translator, car phone , Portable printer, transceiver, pager, handy terminal, portable copy, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, handy cleaner, portable compact disc (CD) player, video movie, navigation system, etc. It can be used as a power source for equipment.
In addition, lighting equipment, air conditioners, TVs, stereos, water heaters, refrigerators, microwave ovens, dishwashers, washing machines, dryers, game machines, toys, road conditioners, medical equipment, automobiles, electric vehicles, golf carts, It can be used as a power source for electric carts, power storage systems, and the like.
Further, the application is not limited to civilian use, but may also be for military use or space use.
The non-aqueous electrolyte secondary battery of the present invention is particularly excellent as a power source for electric vehicles and hybrid cars, and at this time, exhibits excellent cycle characteristics and safety.
In electric vehicles and hybrid cars, there is a danger that not only the engine or the motor will heat up and the battery will ignite, but also the battery will ignite when it becomes hot due to outside air. Such a danger can be avoided by using the non-aqueous electrolyte secondary battery of the present invention.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

1. Preparation of negative electrode active material [Example 1]
A lithium compound, a titanium compound, and a magnesium compound were mixed such that each constituent element had a predetermined composition ratio. The obtained mixture was calcined at 810 ° C. for 12 hours in the atmosphere. Thus, a negative electrode active material was obtained.
The composition of the obtained negative electrode active material determined by ICP spectroscopy was Li _1.26 Ti _1.72 Mg _0.02 O ₄ .

[Example 2]
A lithium compound, a titanium compound, a magnesium compound, and an aluminum compound were mixed such that each constituent element had a predetermined composition ratio. The obtained mixture was calcined at 810 ° C. for 12 hours in the atmosphere. Thus, a negative electrode active material was obtained.
Composition by ICP spectrometry of the negative electrode active material thus obtained was _{Li 1.26 Ti 1.73 Mg 0.02 Al 0.011} O 4.

[Example 3]
A lithium compound, a titanium compound, a magnesium compound, and a boron compound were mixed such that each constituent element had a predetermined composition ratio. The obtained mixture was calcined at 810 ° C. for 12 hours in the atmosphere. Thus, a negative electrode active material was obtained.
The composition of the obtained negative electrode active material determined by ICP spectroscopy was Li _1.20 Ti _1.58 Mg _0.02 B _0.004 O ₄ .

[Example 4]
A lithium compound, a titanium compound, a magnesium compound, and a fluorine compound were mixed so that each constituent element had a predetermined composition ratio. The obtained mixture was calcined at 810 ° C. for 12 hours in the atmosphere. Thus, a negative electrode active material was obtained.
The composition of the obtained negative electrode active material determined by ICP spectroscopy was Li _1.29 Ti _1.80 Mg _0.02 F _0.006 O ₄ .

[Example 5]
A lithium compound, a titanium compound, a magnesium compound, and a sulfur compound were mixed so that each constituent element had a predetermined composition ratio. The obtained mixture was calcined at 810 ° C. for 12 hours in the atmosphere. Thus, a negative electrode active material was obtained.
The composition of the obtained negative electrode active material by ICP spectroscopy was Li _1.27 Ti _1.81 Mg _0.02 S _0.014 O ₄ .

[Example 6]
A lithium compound, a titanium compound, a magnesium compound, and a zirconium compound were mixed such that each constituent element had a predetermined composition ratio. The obtained mixture was calcined at 810 ° C. for 12 hours in the atmosphere. Thus, a negative electrode active material was obtained.
The composition of the obtained negative electrode active material was Li _1.17 Ti _1.66 Mg _0.02 Zr _0.008 O ₄ .

[Comparative Example 1]
A lithium compound and a titanium compound were mixed such that each constituent element had a predetermined composition ratio. The obtained mixture was calcined at 810 ° C. for 12 hours in the atmosphere. Thus, a negative electrode active material was obtained.
The composition of the obtained negative electrode active material was Li _1.27 Ti _1.58 O ₄ .

2. Evaluation of Negative Electrode Active Material Using each of the negative electrode active materials obtained above, a test secondary battery was prepared and evaluated as follows.
The test secondary battery was manufactured as follows.
A paste was prepared by kneading 90 parts by weight of the negative electrode active material powder, 5 parts by weight of carbon powder to be a conductive agent, and a normal methylpyrrolidone solution of polyvinylidene fluoride (5 parts by weight as polyvinylidene fluoride amount). Was applied to a current collector and dried to obtain an electrode plate. Using the obtained electrode plate, a test secondary battery whose counter electrode was lithium was produced.
In the evaluation of the present invention, the reaction of inserting lithium into the negative electrode active material was defined as charging, and the reaction of desorbing lithium was defined as discharging.

(1) Load Discharge Capacity Under the conditions of a charge potential of 1.0 V, a discharge potential of 3.0 V, and a discharge load of 2.0 C, a test secondary battery whose negative electrode was lithium metal was discharged. The discharge capacity at this time was defined as a load discharge capacity. The higher the value, the better the load characteristics.

(2) Heating start temperature Charging / discharging with a constant current was carried out to make it fit. Thereafter, the test secondary battery was charged under a constant current until the battery voltage reached 1.0 V. After the charging was completed, the positive electrode was taken out of the test secondary battery, washed and dried, and the negative electrode active material was scraped off from the negative electrode. About 2 mg of ethylene carbonate used for the electrolyte and about 5 mg of a positive electrode active material scraped from the positive electrode were weighed in an Al cell, and the differential scanning calorimetry was measured.
Differential scanning calorimetry is a method of measuring the difference between the energy input of a substance and a reference substance as a function of the temperature while changing the temperature of the substance and the reference substance according to a program. Although the calorific value does not change, the differential scanning calorific value greatly increases at a certain temperature or higher. The temperature at this time is defined as the heat generation start temperature, and the higher the temperature, the better the thermal stability.

The results are shown in Table 1. In the table, "-" indicates that the corresponding item was not measured.
As is clear from Table 1, the negative electrode active materials obtained in Example 3, Example 4, Example 5, and Example 6 were excellent in load characteristics. Further, the negative electrode active materials obtained in Example 1 and Example 5 were excellent in thermal stability.
Further, the negative electrode active material of the present invention has excellent cycle characteristics.

The negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention can be used for a non-aqueous electrolyte secondary battery.
The non-aqueous electrolyte secondary battery of the present invention can be used as a power source for mobile devices such as mobile phones, notebook computers, digital cameras, and the like, and for batteries for electric vehicles and the like.

FIG. 1 is a schematic diagram showing a crystal structure of a lithium transition metal composite oxide having a spinel structure. FIG. 2 is a schematic sectional view of the negative electrode. FIG. 3 is a schematic sectional view of a cylindrical battery. FIG. 4 is a schematic partial cross-sectional view of the coin-type battery. FIG. 5 is a schematic perspective sectional view of a prismatic battery.

Explanation of reference numerals

1 8a site 2 32e site 3 16d site 4 Binder 5 Negative electrode active material 11 Negative electrode 12 Current collector 13 Positive electrode 14 Separator 20 Cylindrical battery 30 Coin battery 40 Square battery

Claims (12)

A negative electrode active material for a non-aqueous electrolyte secondary battery having a lithium transition metal composite oxide having a spinel structure containing an alkali metal and / or an alkaline earth metal. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the transition metal of the lithium transition metal composite oxide comprises two or more types. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium transition metal composite oxide contains aluminum. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium transition metal composite oxide contains boron. The negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the lithium transition metal composite oxide includes at least one selected from the group consisting of fluorine, chlorine, bromine, and iodine. The negative electrode active material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the lithium transition metal composite oxide contains sulfur. The number of the lithium transition metal composite oxide is represented by the general formula _{Li a Ti b O 4 + c} (a is a number satisfying 0.8 ≦ a ≦ 1.5, b is satisfying 1.5 ≦ b ≦ 2.2 And c represents a number satisfying -0.5 ≦ c ≦ 0.5.) The negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6. The lithium transition metal composite oxide is represented by the general formula _{Li a Ti b M d O 4} + c (2 Group wherein, M is one or more transition metals other than titanium, of the periodic table, Group 13 and Group 14 elements, halogen Represents at least one element selected from the group consisting of elements and sulfur, a + d represents a number satisfying 0.8 ≦ a + d ≦ 1.5, and b represents a number satisfying 1.5 ≦ b ≦ 2.2 , D represents a number that satisfies 0 ≦ d ≦ 0.1, and c represents a number that satisfies −0.5 ≦ c ≦ 0.5.) Negative electrode active material for non-aqueous electrolyte secondary batteries. The negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 8, wherein the lithium transition metal composite oxide is a particle and has a sulfate group on at least the surface of the particle. The lithium transition metal composite oxide used for the negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 9,
A negative electrode active material for a non-aqueous electrolyte secondary battery having Al ₂ O ₃ and / or LiTiO ₂ on at least a part of its surface. A non-aqueous electrolyte secondary battery using the negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1. A non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the following I is used as a positive electrode active material of the positive electrode, and the following II is used as a negative electrode active material of the negative electrode.
I: formula _{Li 1 + e Mn 2-e} O 4 + f (e represents a number satisfying -0.2 ≦ e ≦ 0.2, f is a number satisfying -0.5 ≦ f ≦ 0.5.) ,
Li _g WO _h (W represents Co and / or Mn, g is a number satisfying 0.8 ≦ g ≦ 1.2, h is a number satisfying 1.8 ≦ h ≦ 2.2.) ,
_{Li i Ni j Co k X (} 1-j-k) O l (X is Al or Mn, i represents a number satisfying 0.95 ≦ i ≦ 1.10, j is 0.1 ≦ j ≦ 0. 9 represents a number that satisfies 9, 9 represents a number that satisfies 0.1 ≦ k ≦ 0.9, and 1 represents a number that satisfies 1.8 ≦ l ≦ 2.2.)
The number _{Li m Mn n Y 3-m} -n O 4 + o (Y is at least one selected from the group consisting of Co, Fe, Cu, Cr and Ni, m is satisfying 0.8 ≦ m ≦ 1.2 And n represents a number satisfying 0.5 ≦ n ≦ 1.5, and o represents a number satisfying −0.5 ≦ o ≦ 0.5.)
And Li _p Z _q PO _{4 + r} (Z represents Co and / or Fe, p represents a number satisfying 0.8 ≦ p ≦ 1.2, and q represents a number satisfying 0.9 ≦ q ≦ 1.1. And r represents a number satisfying −0.2 ≦ r ≦ 0.2.)
A positive electrode active material for a non-aqueous electrolyte secondary battery having at least one lithium transition metal composite oxide selected from the group consisting of:
II: The negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 10.

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