JP2005071680A - Positive electrode active material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material for a nonaqueous electrolyte secondary battery and the nonaqueous electrolyte secondary battery having battery property excellent under severer use environment. <P>SOLUTION: This positive electrode active material for nonaqueous electrolyte secondary batteries has at least a lithium transition-metal composite oxide of a spinel structure. The lithium transition-metals composite oxide is represented by general formula Li<SB>1+a</SB>Mg<SB>b</SB>Ti<SB>c</SB>Mn<SB>2-a-b-c</SB>O<SB>4+e</SB>(where a is a number satisfying -0.2≤a≤0.2, b is a number satisfying 0.005≤b≤0.10, c is a number satisfying 0.005≤c≤0.05 and e is a number satisfying -0.5≤e≤0.5), the lithium transition-metal composite oxide is a particle. The Mn/Mg molar ratio of the surface on the particle is less than (2-a-b-c)/b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery (hereinafter also simply referred to as “positive electrode active material”) and a non-aqueous electrolyte secondary battery. Specifically, the present invention relates to a lithium transition metal composite oxide having a spinel structure in which battery characteristics are greatly improved.

Non-aqueous electrolyte secondary batteries are characterized by higher operating voltage and higher energy density than conventional nickel cadmium secondary batteries, and are widely used as power sources for mobile electronic devices. As the positive electrode active material of this non-aqueous electrolyte secondary battery, lithium transition metal composite oxides typified by LiCoO ₂ , LiNiO ₂ and LiMn ₂ O ₄ are used.

  However, at present, mobile devices such as mobile phones, notebook computers, and digital cameras have a more severe usage environment due to high functionality such as the addition of various functions and use at high and low temperatures. It has become a thing. In addition, application to power sources such as batteries for electric vehicles is expected. Conventional non-aqueous electrolyte secondary batteries cannot obtain sufficient battery characteristics, and further improvements are required.

In Patent Document 1, a part of the transition element Me in the lithium transition element composite oxide LiMe _x O _y is Li, Fe, Mn, Ni, Mg, Zn, B, Al, Co, Cr, Si, Ti, LiM _z Me _x-z O _y formed by substitution with two or more elements selected from Sn, P, V, Sb, Nb, Ta, Mo, W (where M is a substitution element and M ≠ Me , Z represents a substitution amount.) As a positive electrode active material. This positive electrode active material improves the electron conductivity of the positive electrode active material itself and reduces the internal resistance of the battery. At the same time, LiMn ₂ O ₄ has a reversible crystal structure with respect to insertion / extraction of Li ^+. Therefore, it is described that the cycle characteristics as a battery are improved. In addition, when at least Ti is included as the substitution element M, the effect of improving the electron conductivity is remarkably obtained, and it is preferable that Ti can be effectively used for preventing the decrease in the positive electrode capacity, and it is preferable. ing.

  However, with this positive electrode active material, battery characteristics at a sufficiently high temperature under a more severe use environment could not be obtained. Further, sufficient charge / discharge capacity could not be obtained, and sufficient cycle characteristics and load characteristics at room temperature could not be obtained.

JP 2000-90933 A

  An object of the present invention is to provide a positive 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.

The positive electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure, and the lithium transition metal The composite oxide is represented by the general formula Li _{1 + a} Mg _b Ti _c Mn _2-a-b-c O _{4 + e} (a is a number satisfying −0.2 ≦ a ≦ 0.2, and b is 0.005 ≦ b ≦ 0.10 represents a number satisfying 0.10, c represents a number satisfying 0.005 ≦ c ≦ 0.05, e represents a number satisfying −0.5 ≦ e ≦ 0.5), and The lithium transition metal composite oxide is a particle and has a Mn / Mg molar ratio of less than (2-abc) / b on the surface of the particle.

  The positive electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure, and the lithium transition metal The composite oxide is a particle, and the concentration of boron present on the surface of the particle is greater than the concentration of boron present inside the particle, and the concentration of magnesium present on the surface of the particle is The concentration of magnesium present inside the particles is greater than the concentration of titanium present in the particles, and the concentration of magnesium present in the particles is greater than the concentration of boron present in the particles. Greater than the concentration of boron present inside.

  The positive electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure, and the lithium transition metal The composite oxide is a lithium transition metal composite oxide which is a particle and has boron and magnesium and titanium at least on the surface of the particle.

  The boron content is 0.4 to 55.6% by weight based on the total of boron, titanium, and magnesium, and the magnesium content is 3. It is 7-97.0 weight%, and it is preferable that content of the said titanium is 2.1-95.2 weight% with respect to the sum total of boron, titanium, and magnesium.

  The (400) crystallite diameter of the lithium transition metal composite oxide is preferably 700 to 1100 mm.

  The non-aqueous electrolyte secondary battery described in the present invention has a positive electrode active material layer using the positive electrode active material for a non-aqueous electrolyte secondary battery according to any of the present invention as a positive electrode active material. And a negative electrode active material layer using a metal lithium, lithium alloy, or a compound capable of occluding and releasing lithium ions as a negative electrode active material on each side of the band negative electrode current collector. A strip-shaped negative electrode configured by forming a strip-shaped separator, and the strip-shaped positive electrode and the strip-shaped negative electrode are wound a plurality of times in a state where the strip-shaped positive electrode and the strip-shaped negative electrode are stacked via the strip-shaped separator. A spiral wound body in which the belt-like separator is interposed therebetween.

In the present invention, the distribution state of Mg and Ti in the lithium manganate crystal is controlled.
When Mg is dissolved in lithium manganate, the high-temperature cycle characteristics are improved, but + trivalent manganese ions are decreased, so that the charge / discharge capacity is decreased. Therefore, in the present invention, the Mg concentration is inclined on the surface and inside of the lithium manganate particles.
That is, by setting the Mn / Mg molar ratio of the surface of the lithium transition metal composite oxide particles to less than (2-abc) / b, the reduction in charge / discharge capacity due to Mg solid solution is within a practical level. And elution of Mn ions into the electrolytic solution can be suppressed. This improves the high temperature cycle characteristics.
However, it is difficult to obtain sufficient load characteristics and cycle characteristics, although the high-temperature cycle characteristics are improved only by inclining the Mg concentration on the surface and inside of the particles.
Therefore, in the present invention, Ti is dissolved in lithium manganate. By dissolving Ti, the lattice constant of lithium manganate can be increased. Thus, it is considered that the load characteristics are improved because the diffusibility of Li ions in the lithium manganate crystal is improved without impairing the improvement of the high-temperature cycle characteristics. In addition, the improvement in the diffusibility of Li ions is considered to suppress the distortion of the lithium manganate crystal due to the charge / discharge cycle, so that the cycle characteristics are also improved.

The concentration of boron present on the surface of lithium transition metal composite oxide particles (hereinafter also simply referred to as “particles”) is greater than the concentration of boron present inside the particles, so that the primary particles of the particles can be effectively obtained. Diameter can be grown. Thereby, the packing property of particle | grains can be improved and an electrode plate density can be improved. Therefore, the charge / discharge capacity per unit volume of the battery is improved.
The concentration of magnesium present on the surface of the particles is greater than the concentration of magnesium present inside the particles, limiting the decrease in charge / discharge capacity to a practical level, and elution of transition metal ions into the electrolyte. It is thought that it can be suppressed. Thereby, the high-temperature cycle characteristics are improved.
Since the concentration of titanium existing inside the particles is larger than the concentration of boron existing inside the particles, the lattice constant of the lithium transition metal composite oxide can be increased without impairing the growth of the primary particle diameter. . Thereby, load characteristics and cycle characteristics are improved.
Suppressing elution of transition metal ions into the electrolyte without impairing the growth of the primary particle size because the concentration of magnesium present inside the particles is greater than the concentration of boron present inside the particles. Can do. Thereby, the improvement of an electrode plate density and the improvement of a high temperature cycling characteristic can be aimed at.

By having boron on the surface of the particles, the primary particle diameter can be effectively grown.
In addition, by containing magnesium and titanium, it is possible to suppress the elution of transition metal ions into the electrolyte without impairing the growth of the primary particle diameter, and to increase the lattice constant of the lithium transition metal composite oxide. Can do.
Thereby, an electrode plate density can be improved and a high temperature cycling characteristic, a load characteristic, and cycling characteristics can be improved.

  The boron content is 0.4 to 55.6% by weight with respect to the total of boron, titanium, and magnesium, and the magnesium content is 3.7 to 0.7% with respect to the total of boron, titanium, and magnesium. 97.0% by weight, and the content of titanium is 2.1 to 95.2% by weight based on the total of boron, titanium, and magnesium. Both improvement in cycle characteristics and load characteristics can be achieved. Moreover, it is thought that when the titanium content is in the above range, the diffusibility of lithium ions is further improved, and the internal resistance in the positive electrode active material can be reduced. This improves the average potential.

  When the (400) crystallite diameter of the lithium transition metal composite oxide is 700 to 980 mm, cycle characteristics and load characteristics can be further improved.

  A strip-shaped positive electrode configured by forming a positive electrode active material layer using the positive electrode active material for a non-aqueous electrolyte secondary battery according to any of the present invention as a positive electrode active material on both surfaces of the strip-shaped positive electrode current collector, Constructed by forming negative electrode active material layers using metallic lithium, lithium alloy, carbon material capable of occluding and releasing lithium ions, or compounds capable of occluding and releasing lithium ions as negative electrode active materials on both sides of the strip-shaped negative electrode current collector, respectively. The strip-shaped negative electrode and the strip-shaped separator are wound, and the strip-shaped positive electrode and the strip-shaped negative electrode are wound a plurality of times in a state of being laminated via the strip-shaped separator, and the band-shaped positive electrode and the strip-shaped negative electrode are By constructing a spiral wound body with a strip separator interposed therebetween, the manufacturing process is simplified, and cracks in the positive electrode active material layer and the negative electrode active material layer can be obtained. It is less likely to occur in the peeling. Thereby, battery capacity and energy density can be improved. In addition, since the adhesion between the positive electrode and the negative electrode is improved, the nonaqueous electrolyte secondary battery is further excellent in high-temperature cycle characteristics, cycle characteristics, and load characteristics.

  Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery and the 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 this embodiment, examples, and FIGS.

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

  Examples of the spinel structure lithium transition metal composite oxide include lithium manganese composite oxide and lithium titanium composite oxide. Among these, lithium manganese composite oxide is preferable.

  In the positive electrode active material of the present invention, the lithium transition metal composite oxide is present in the form of particles. Specifically, the lithium transition metal composite oxide is present 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 only of primary particles, or may be composed only of secondary particles that are aggregates of primary particles. It may consist of both particles and secondary particles.

In the present invention, the concentrations of boron, magnesium, and titanium present on the surface and inside of the particles can be analyzed by various methods. For example, it can analyze by Auger Electron Spectroscopy (AES: Auger Electron Spectroscopy).
For example, it can be quantified by combining Auger electron spectroscopy, inductively coupled plasma (ICP) spectroscopy, and titration.

In the present invention, a lithium transition metal composite oxide having boron at least on the surface of the particles is preferable.
Boron exhibits the effects of the present invention regardless of the form of boron present on the surface of the lithium transition metal composite oxide particles. For example, even when boron covers the entire particle surface or boron covers a part of the particle surface, the electrode plate density can be improved.
Further, boron may be present at least on the surface of the particle. Therefore, a part of boron may be present inside the particles. The presence state of boron on the surface of the particle is not particularly limited. It may exist in the state of a boron compound. As the boron compound, lithium borate is preferable.
Whether boron is present on the surface of the particle can be analyzed by various methods. For example, it can be analyzed by Auger Electron Spectroscopy (AES) or X-ray Photoelectron Spectroscopy (XPS).

  In the present invention, it suffices to have titanium, and it may be present on the surface of the particle or may be dissolved in the particle. The presence state of titanium on the surface of the particle is not particularly limited. It may exist in the state of a titanium compound. As the titanium compound, titanium oxide and lithium titanate are preferable.

  In this invention, it is preferable to have magnesium. Magnesium may be present on the surface of the particle or may be dissolved in the particle. The presence state of magnesium on the surface of the particle is not particularly limited. It may exist in the state of a magnesium compound. As a magnesium compound, magnesium oxide, magnesium carbonate, and magnesium hydroxide are preferable.

  In the present invention, the “surface of the lithium transition metal composite oxide particle” means a depth of 0 μm or more and 0.1 μm or less from the surface of the lithium transition metal composite oxide particle.

In the present invention, the boron content is preferably 1.0% by weight or more, more preferably 2.0% by weight or more with respect to the total of boron, titanium and magnesium, and 16.0%. It is preferably no more than wt%, more preferably no more than 8.0 wt%.
When there is too much content of boron, initial capacity will fall. In addition, the elution of transition metal ions increases, causing gas generation, resulting in deterioration of high temperature characteristics. If the boron content is too small, the primary particle size will not grow, and the particle packing property will not be improved.

In the present invention, the magnesium content is preferably 8.0% by weight or more, more preferably 30.0% by weight or more based on the total of boron, titanium and magnesium, and 83.0%. It is preferably no more than wt%, more preferably no more than 75.0 wt%.
If the magnesium content is too high, the amount of magnesium that cannot be completely dissolved in the transition metal site increases, and the initial capacity decreases. If the magnesium content is too low, the elution of transition metal ions increases and causes gas generation, which deteriorates the high temperature characteristics.

In the present invention, the titanium content is preferably 8.0% by weight or more, more preferably 20.0% by weight or more based on the total of boron, titanium and magnesium, and 90.0%. It is preferably not more than wt%, more preferably not more than 55.0 wt%.
When there is too much content of titanium, a charge / discharge high rate will fall. If the titanium content is too small, sufficient load characteristics and cycle characteristics cannot be obtained.

  In the present invention, various methods can be used for determination of boron, magnesium and titanium. For example, it can be quantified by inductively coupled plasma (ICP) spectroscopy or titration.

  In the positive electrode active material of the present invention, the transition metal is preferably manganese. When the transition metal is manganese, the non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention has excellent cycle characteristics, high-temperature cycle characteristics, and load characteristics. It can be particularly preferably used. Moreover, since it becomes the thing excellent also in the output characteristic, it can use especially suitably also for the use of an electric vehicle.

The positive electrode active material of the present invention is preferably a lithium manganese composite oxide, and when the composition ratio of Li, Mn and O of the lithium manganese composite oxide is represented by the general formula Li _{1 + a} Mn _2−a O _{4 + d} , It is preferable that a represents a number satisfying −0.2 ≦ a ≦ 0.2, and d represents a number satisfying −0.5 ≦ d ≦ 0.5.
a is preferably larger than 0, and is preferably 0.15 or less. It is considered that the cycle characteristics are further improved by substituting a part of manganese with lithium.

  In the positive electrode active material of the present invention, the following (i) to (iv) are mentioned as preferred embodiments of the lithium transition metal composite oxide.

(I) the general formula _{Li 1 + a Mg b Ti c} Mn 2-a-b-c B d O 4 + e (a represents a number satisfying -0.2 ≦ a ≦ 0.2, b is 0.005 ≦ b ≦ 0.10 represents a number satisfying 0.10, c represents a number satisfying 0.005 ≦ c ≦ 0.05, d represents a number satisfying 0.002 ≦ d ≦ 0.02, and e represents −0.5 ≦ e represents a number satisfying e ≦ 0.5.)

Aspect (i) is excellent in cycle characteristics, high temperature cycle characteristics and load characteristics.
In embodiment (i), a is preferably greater than 0. It is considered that the cycle characteristics are improved by substituting a part of manganese with lithium.
In the embodiment (i), b is preferably 0.01 or more, more preferably 0.02 or more, and preferably 0.08 or less, and 0.07 or less. More preferred. If b is too large, + 3-valent manganese ions decrease, and the charge / discharge capacity decreases. If b is too small, elution of transition metal ions increases and gas generation occurs, so that the high temperature characteristics deteriorate.
In the embodiment (i), c is preferably 0.01 or more, more preferably 0.02 or more, and preferably 0.08 or less, and 0.07 or less. More preferred. When c is too large, the charge / discharge rate decreases. If c is too small, sufficient load characteristics and cycle characteristics cannot be obtained.
In the embodiment (i), d is preferably 0.003 or more, and is preferably 0.008 or less. If d is too large, the initial capacity decreases. In addition, the elution of transition metal ions increases, causing gas generation, resulting in deterioration of high temperature characteristics. If d is too small, the primary particle size does not grow, and the particle packing property is not improved.

  (Ii) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium.

  By having at least one selected from the group consisting of titanium, zirconium, and hafnium, the lattice constant of the unit cell of the lithium manganese composite oxide particle increases, the mobility of lithium ions in the particle increases, and the impedance decreases. I think it can be done. For this reason, it is thought that output characteristics improve, without impairing improvement of cycling characteristics and high temperature cycling characteristics.

  In the embodiment (ii), it is preferable that the lithium transition metal composite oxide has zirconium at least on the surface of the particles. Presence of zirconium on the surface of the particles is considered to reduce interface resistance and improve load characteristics and low temperature characteristics. Further, it is considered that the generation of gas during charging and storage during charging can be suppressed and dry out can be prevented, so that cycle characteristics are improved.

(Iii) The aspect in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium and sulfur.

In the embodiment (iii), it is considered that the cycle characteristics and the load characteristics are further improved since the passage of electrons is improved by the presence of sulfur.
The sulfur content is preferably 0.03 to 0.3% by weight based on the total of the lithium transition metal composite oxide and sulfur. If it is less than 0.03% by weight, it may be difficult to reduce the resistance to movement of electrons. If it exceeds 0.3% by weight, the battery may swell due to moisture adsorption.

Sulfur may be present in any form. For example, it may exist in the form of sulfate radicals.
The sulfate radical includes sulfate ions, a group of atoms obtained by removing the charge from sulfate ions, and sulfo groups. It is preferably based on at least one selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, organic sulfates and organic sulfonic acids and salts thereof.
Among them, it is preferable to use at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferable to use alkali metal sulfates. This is because these are chemically stable because they are composed of strong acid strong base bonds.

In aspect (iii), the reason for containing elements other than sulfur is the same as in aspect (ii).
In the embodiment (iii), by containing each of the above elements, a positive electrode plate having a high charge / discharge capacity and excellent binding properties and surface smoothness can be obtained due to the synergistic effect of each element. .

The lithium transition metal composite oxide may have a sulfate group at least on the surface of the particle.
The presence of the sulfate radical on the surface of the lithium transition metal composite oxide particle makes the electron transfer resistance around the particle extremely small, and as a result, the ease of passing electrons is improved, and the cycle characteristics and load characteristics are improved. It is thought to improve.
In addition, when the positive electrode active material of the present invention is used to form a high voltage battery (for example, a battery using LiMn _1.5 Ni _0.5 O ₄ as a lithium transition metal composite oxide), there is a problem in the conventional high voltage battery. The decomposition of the electrolyte during charging was suppressed, and as a result, the cycle characteristics were improved. The decomposition reaction of the electrolytic solution is thought to occur as a catalyst at the interface between the lithium transition metal composite oxide particles and the electrolytic solution, but the sulfate radical has no function of decomposing the electrolytic solution. Thus, it is considered that the entire surface or part of the surface of the lithium transition metal composite oxide particles reduces the contact area between the electrolytic solution and the catalyst and suppresses the reaction.

  In the present invention, the sulfate group exhibits the effect of the present invention regardless of the form of the sulfate group present on the surface of the lithium transition metal composite oxide particles. For example, even when the sulfate radical covers the entire particle surface of the lithium transition metal composite oxide, the sulfate radical covers a part of the particle surface of the lithium transition metal composite oxide. However, cycle characteristics and load characteristics are improved.

Moreover, the sulfate radical should just exist in the surface of particle | grains at least. Therefore, a part of the sulfate radical may exist inside the particle.
Whether or not the sulfate radical 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 or X-ray photoelectron spectroscopy.
Moreover, various methods can be used for the determination of sulfate radicals. For example, it can be quantified by ICP emission spectrometry or titration.

  (Iv) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium, sulfur, sodium and / or calcium.

In the embodiment (iv), by containing sodium and / or calcium, elution of manganese ions can be further suppressed by a synergistic effect with boron (preferably boron and sulfur), and the practical level is excellent. Cycle characteristics can be realized.
In embodiment (iv), the reason for containing an element other than sodium and / or calcium is the same as in embodiment (ii) and (iii).

  The lithium transition metal composite oxide preferably has an iron content of 25 ppm or less, more preferably 20 ppm or less, and even more preferably 18 ppm or less. If the iron content is too high, it may cause an internal short circuit of the battery.

  In the positive electrode active material of the present invention, the (400) crystallite diameter is preferably 720 mm or more, more preferably 750 mm or more, and preferably 1000 mm or less, more preferably 950 mm or less. preferable. If the (400) crystallite diameter is too large, the lithium ion diffusion path from the inside of the crystal of the lithium transition metal composite oxide particle to the surface of the particle becomes long, so that the internal resistance of the particle increases. In addition, the expansion and contraction of the lithium transition metal composite oxide particles accompanying charging / discharging increase, and the contact with the conductive agent may deteriorate, or the lithium transition metal composite oxide particles themselves may collapse. It is not preferable. When the (400) crystallite size is too small, the cycle characteristics deteriorate because the crystal of the lithium transition metal composite oxide particles collapses every time the charge / discharge cycle is repeated.

Here, “crystallite” means the maximum aggregate that can be considered as a single crystal, and “crystallite diameter” means the size of the crystallite.
Therefore, the larger the crystallite diameter, the better the crystallinity and the less the distortion of the crystal structure. In the lithium transition metal composite oxide having a spinel structure as used in the present invention, the degree of regularity of unit cell arrangement can be shown by the following (400) crystallite diameter.

  The (400) crystallite diameter of the lithium transition metal composite oxide can be determined, for example, by an X-ray diffraction method. The X-ray diffraction method can be performed, for example, under conditions of a tube current of 100 mA and a tube voltage of 40 kV. From the diffraction peak derived from the (400) plane determined by the X-ray diffraction method, the crystallite diameter is calculated by the Scherrer equation represented by the following equation (1).

  D = Kλ / (βcos θ) (1)

  In the above formula, D represents the crystallite size (Å), K represents the Scherrer constant (1.05 when β is calculated from the integral width), and λ represents the wavelength of the X-ray source (in the case of CuKα1). Represents 1.540562Å), β represents the width of the diffraction line spread depending on the crystallite size (radian), and θ represents the diffraction angle (degree).

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

(1) Preparation of raw material mixture The compounds described later are mixed so that each constituent element has a predetermined composition ratio to obtain a raw material mixture. The compound used for the raw material mixture is selected according to the elements constituting the target composition.
The mixing method is not particularly limited, for example, a method of mixing powdery compounds as they are to obtain a raw material mixture; mixing in a slurry form using water and / or an organic solvent, and then drying to obtain a raw material mixture Method: A method in which an aqueous solution of the above-mentioned compound is mixed and precipitated, and the resulting precipitate is dried to obtain a raw material mixture; a method in which these are used in combination.

Below, the compound used for a raw material mixture is illustrated.
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 Examples include lithium, lithium bromide, lithium iodide, and lithium peroxide. Among these, Li ₂ CO ₃ , LiOH, LiOH · H ₂ O, Li ₂ O, LiCl, LiNO ₃ , Li ₂ SO ₄ , LiHCO ₃ , and Li (CH ₃ COO) are preferable.

The manganese compound is not particularly limited. For example, manganese metal, oxide (eg, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ ), hydroxide, nitrate, carbonate (MnCO ₃ ), chloride salt, Examples thereof include manganese iodide, manganese sulfate, and manganese nitrate. Among these, manganese metal, MnCO ₃ , MnSO ₄ , and MnCl ₂ are preferable.

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 iodide, perchlorate Examples include magnesium. Among these, MgSO ₄ and Mg (NO ₃ ) ₂ are preferable.

The titanium compound is not particularly limited. Examples thereof include titanium fluoride, titanium chloride, titanium bromide, titanium iodide, titanium oxide, titanium sulfide, and titanium sulfate. Of these, TiO, TiO ₂ , Ti ₂ O ₃ , TiCl ₂ , and Ti (SO ₄ ) ₂ are preferable.

The boron compound is not particularly limited. For example, B ₂ O ₃ (melting point: 460 ° C.), H ₃ BO ₃ (decomposition temperature: 173 ° C.), lithium boron composite oxide, orthoboric acid, boron oxide, boron phosphate, etc. are used. It is done. Among these, H ₃ BO ₃ and B ₂ O ₃ are preferable.

The zirconium compound is not particularly limited. Examples thereof include zirconium fluoride, zirconium chloride, zirconium bromide, zirconium iodide, zirconium oxide, zirconium sulfide, zirconium carbonate and the like. Of these, ZrF ₂ , ZrCl, ZrCl ₂ , ZrBr ₂ , ZrI ₂ , ZrO, ZrO ₂ , ZrS ₂ , Zr (OH) _{3 and the} like are preferable.

The hafnium compound is not particularly limited. Examples thereof include hafnium fluoride, hafnium chloride, hafnium bromide, hafnium iodide, hafnium oxide, and hafnium carbonate. Among these, HfF ₄ , HfCl ₂ , HfBr ₂ , HfO ₂ , Hf (OH) ₄ , Hf ₂ S and the like are preferable.

The sulfur 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, sulfuric acid and The salt and nitrogen sulfide are mentioned. Among these, Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , and MgSO ₄ are preferable.

Sodium compound is not particularly limited, for _{example, Na 2 CO 3, NaOH,} Na 2 O, NaCl, NaNO 3, Na 2 SO 4, NaHCO 3, CH 3 CONa the like.

Calcium compound is not particularly limited, for _{example, CaO, CaCO 3, Ca (} OH) 2, CaCl 2, CaSO 4, Ca (NO 3) 2, Ca (CH 3 COO) 2 and the like.
Moreover, you may use the compound containing 2 or more types of each element mentioned above.

Hereinafter, a preferred method for obtaining the raw material mixture will be specifically described by taking as an example a positive electrode active material in which the lithium transition metal composite oxide is a lithium manganese composite oxide having magnesium, titanium, and boron.
An aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio prepared from the above-described manganese compound and magnesium compound is dropped into pure water being stirred.
Next, an aqueous ammonium hydrogen carbonate solution is added dropwise to precipitate manganese and magnesium to obtain manganese and magnesium salts. In place of the ammonium hydrogen carbonate aqueous solution, an alkali solution such as a sodium hydroxide aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution, or a lithium hydroxide aqueous solution can also be used.

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound, titanium compound and boron compound to obtain a raw material mixture.

(2) Firing and grinding of 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 according to the purpose.
The firing temperature is preferably 650 ° C. or higher, and more preferably 700 ° C. or higher. If the firing temperature is too low, unreacted raw materials may remain in the positive electrode active material, and the original characteristics of the positive electrode active material may not be utilized. The firing temperature is preferably 1100 ° C. or lower, and more preferably 950 ° C. or lower. If the firing temperature is too high, the particle size of the positive electrode active material may become too large, and the battery characteristics may deteriorate. In addition, by-products such as Li ₂ MnO ₃ and LiMnO ₂ are likely to be generated, which may lead to a decrease in discharge capacity per unit weight, a decrease in cycle characteristics, and a decrease in operating voltage.
In general, the firing time is preferably 1 to 24 hours, and more preferably 6 to 12 hours. When the firing time is too short, the diffusion reaction between the raw material particles does not proceed. If the firing time is too long, firing after the diffusion reaction is almost completed is wasted, and coarse particles may be formed by sintering.

  The firing may be divided into a plurality of firing steps. For example, a 1st baking process can be performed at 350-550 degreeC for 1 to 24 hours, and a 2nd baking process can be performed at 650-1000 degreeC for 1 to 24 hours.

  Examples of the firing atmosphere include air, oxygen gas, a mixed gas of these 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 weak oxidizing atmosphere. Among these, an atmosphere in which the oxygen concentration is controlled is preferable.

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

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

The positive electrode active material of the present invention is suitably used for non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries and lithium ion polymer secondary batteries.
That is, the non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention. The non-aqueous electrolyte secondary battery of the present invention only needs to use the positive electrode active material of the present invention as at least a part of the positive electrode active material.
Hereinafter, a lithium ion secondary battery will be described as an example.

  As the negative electrode active material, metallic lithium, a lithium alloy, or a compound capable of occluding and releasing lithium ions can be used. Examples of the lithium alloy include a LiAl alloy, a LiSn alloy, and a LiPb alloy. Examples of the carbon material capable of occluding and releasing lithium ions include carbon materials such as graphite and graphite. Examples of the compound capable of occluding and releasing lithium ions include oxides such as tin oxide and titanium oxide.

The electrolyte solution is not particularly limited as long as it is a compound that does not change or decompose with 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 admixture of two or more.

Examples of the electrolyte include lithium salts such as lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium trifluoromethanoate.
The above-described solvent and electrolyte are mixed to obtain an electrolytic solution. Here, a gelling agent or the like may be added and used as a gel. Moreover, you may make it absorb and use for the polymer which has liquid absorptivity. Further, a solid electrolyte having conductivity of inorganic or organic lithium ions may be used.

  Examples of the separator include a porous film made of polyethylene or polypropylene.

  Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyamide acrylic resin, and the like.

Using the positive electrode active material of the present invention and the above-described negative electrode active material, electrolytic solution, separator, and binder, a lithium ion secondary battery can be obtained according to a conventional method.
Thereby, the outstanding battery characteristic which was not able to be achieved conventionally is realizable.

  As the positive electrode active material, lithium cobaltate and / or lithium nickelate can be used together with the positive electrode active material of the present invention. As a result, a non-aqueous electrolyte secondary battery having high charge / discharge capacity and excellent cycle characteristics, load characteristics and output characteristics can be obtained.

Lithium cobaltate represented by the general formula Li _{1 + x} CoO ₂ (x represents a number satisfying −0.5 ≦ x ≦ 0.5) is preferable. The lithium cobaltate is at least a part selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum and tin. It may be substituted with one kind.

Lithium nickelate represented by the general formula Li _{1 + x} NiO ₂ (x represents a number satisfying −0.5 ≦ x ≦ 0.5) is preferable. The lithium nickelate is at least a part selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum and tin. It may be substituted with one kind.

  The lithium cobaltate and / or lithium nickelate used together with the positive electrode active material of the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide. The following (i)-(iii) are mentioned as a suitable aspect of this lithium transition metal complex oxide.

(I) the lithium transition metal composite oxide has a 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 represents a number satisfying 0.95 ≦ v ≦ 1.05, w satisfies 0 <w ≦ 0.10 when 0 or M ¹ is Al, and 0 <w ≦ 0 when M ¹ is Ti. .05 represents a number satisfying 0 <x ≦ 0.10, y represents a number satisfying 1 ≦ y ≦ 2.5, and z satisfying 0 <z ≦ 0.015 The aspect represented by this.

  By combining the positive electrode active material having this lithium transition metal composite oxide and the positive electrode active material of the present invention, a battery having not only excellent high-temperature cycle characteristics, load characteristics and cycle characteristics but also high capacity and safety can be obtained. Can be obtained.

(Ii) The lithium transition metal composite oxide is at least selected from the group consisting of Li _a Co _{1- b} MbO _{c Xd} S _e (M is Ti, Al, V, Zr, Mg, Ca and Sr) 1 represents at least one 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). Aspect.

  By combining the positive electrode active material having this lithium transition metal composite oxide and the positive electrode active material of the present invention, a battery having not only excellent high-temperature cycle characteristics, load characteristics and cycle characteristics but also high capacity and safety can be obtained. Can be obtained.

  (Iii) The lithium transition metal composite oxide is at least one selected from the group consisting of lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate, and nickel cobalt lithium manganate, and is a particle. A mode in which the abundance ratio of zirconium on the surface is 20% or more.

  By combining the positive electrode active material having this lithium transition metal composite oxide and the positive electrode active material of the present invention, not only is it excellent in high temperature cycle characteristics, load characteristics and cycle characteristics, but also low temperature characteristics, high capacity and safety are excellent. A battery can be obtained.

In this positive electrode active material, the proportion of zirconium present on the surface of the particles is 20% or more. Details will be described below.
In the present invention, the “ratio of zirconium present on the surface of the lithium transition metal composite oxide particles” is determined as follows.
First, the presence state of zirconium on the surface of the particles of the lithium transition metal composite oxide particles is observed with an electron beam microanalyzer (EPMA) equipped with a wavelength dispersive X-ray spectrometer (WDX). Next, in the observation field of view, select the part with the largest amount of zirconium per unit area (the part where the zirconium peak is large), and perform line analysis along the line segment that passes through this part (for example, the line segment with a length of 300 μm). I do. In line analysis, the quotient obtained by dividing the total length of the portions where the peak is 4% or more when the peak value in the portion having the largest amount of zirconium per unit area is 100% by the length of the line segment. Is the “ratio of zirconium present on the surface of the lithium transition metal composite oxide particles”. In addition, it is preferable to use the average value of “the zirconium abundance ratio 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, the portion where the peak of zirconium is less than 4% has a large difference from the portion where the amount of zirconium is the largest, and therefore is regarded as a portion where zirconium does not exist.

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

A preferred method for producing a positive electrode using the positive electrode active material of the present invention will be described below.
A positive electrode mixture is prepared by mixing the positive electrode active material powder of the present invention with a carbon-based conductive agent such as acetylene black and graphite, a binder, and a binder solvent or dispersion medium. The obtained positive electrode mixture is made into a slurry or a kneaded product, applied to or supported on a current collector such as an aluminum foil, and press-rolled to form a positive electrode active material layer on the current collector.
FIG. 2 is a schematic cross-sectional view of the positive electrode. As shown in FIG. 2, the positive electrode 13 is obtained by holding the positive electrode active material 5 on the current collector 12 with the binder 4.

It is considered that the positive electrode active material of the present invention is excellent in mixing with the conductive agent powder and has a low internal resistance of the battery. Accordingly, the charge / discharge characteristics, particularly the discharge capacity, are excellent.
In addition, the positive electrode active material of the present invention is excellent in fluidity when kneaded with a binder, and is easily entangled with a polymer of the binder and has excellent binding properties.
Furthermore, since the positive electrode active material of the present invention does not contain coarse particles and is spherical, the surface of the coating film surface of the produced positive electrode has excellent smoothness. For this reason, the coating film surface of a positive electrode plate is excellent in binding property, and becomes difficult to peel off. In addition, since the surface is smooth and lithium ions are uniformly introduced and exited on the surface of the coating film accompanying charging / discharging, the cycle characteristics are remarkably improved.

The shape of the lithium ion secondary battery is not particularly limited, and may be a cylindrical shape, a coin shape, a square shape, a laminate shape, or the like.
FIG. 3 is a schematic cross-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 a coin-type battery. As shown in FIG. 4, in the coin-type battery 30, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12 and the negative electrode 11 are stacked via the separator 14.
FIG. 5 is a schematic perspective view of a prismatic battery. As shown in FIG. 5, in the square 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. However, they are repeatedly laminated via the separator 14.

A non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the following I is used as the positive electrode active material of the positive electrode and the following II is used as the negative electrode active material of the negative electrode Can be obtained.
I: Lithium transition metal composite oxide used for the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, and a general formula of Li _{1 + x} CoO ₂ (x is −0.5 ≦ x ≦ 0.5) Lithium cobaltate represented by lithium cobaltate and / or general formula Li _{1 + x} NiO ₂ (x represents a number satisfying −0.5 ≦ x ≦ 0.5). When the weight of the lithium transition metal composite oxide is A and the weight of the lithium cobaltate and / or the lithium nickelate is B, the range is 0.2 ≦ B / (A + B) ≦ 0.8. A positive electrode active material for a non-aqueous electrolyte secondary battery to be mixed.
II: A negative electrode active material for a non-aqueous electrolyte secondary battery comprising at least one selected from the group consisting of metallic lithium, lithium alloys and compounds capable of occluding and releasing lithium ions.

This non-aqueous electrolyte secondary battery has a high electrode plate density and is excellent not only in cycle characteristics and high-temperature cycle characteristics but also in load characteristics and output characteristics.
The positive electrode active material is preferably mixed so that 0.4 ≦ B / (A + B) ≦ 0.6. If it is in the range of 0.4 ≦ B / (A + B) ≦ 0.6, not only the electrode plate density, the prevention of dryout and the improvement of overcharge characteristics, but also the improvement of cycle charge / discharge characteristics, load characteristics and output characteristics can be achieved. Because it is remarkable.
As a compound capable of occluding and releasing lithium ions, a general formula consisting of a spinel structure containing an alkali metal and / or an alkaline earth metal is Li _a Ti _b O _{4 + c} (a is a number satisfying 0.8 ≦ a ≦ 1.5. B represents a number satisfying 1.5 ≦ b ≦ 2.2, and c represents a number satisfying −0.5 ≦ c ≦ 0.5.) A negative electrode active material can be used. At this time, a non-aqueous electrolyte secondary battery with greatly improved cycle characteristics can be obtained.

The application of the nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention is not particularly limited. For example, notebook computers, pen input computers, pocket computers, notebook word processors, pocket word processors, electronic book players, mobile phones, cordless phones, electronic notebooks, calculators, LCD TVs, electric shavers, electric tools, electronic translators, car phones , 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.
Also, lighting equipment, air conditioner, TV, stereo, water heater, refrigerator, oven microwave, dishwasher, washing machine, dryer, game machine, toy, road conditioner, medical equipment, automobile, electric car, golf cart, It can be used as a power source for electric carts, power storage systems and the like.
Furthermore, the application is not limited to consumer use, and may be used for military use or space.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

1. Preparation of positive electrode active material [Example 1]
Manganese and magnesium carbonates were washed with water, dried, and then mixed with orthoboric acid, titanium oxide and lithium carbonate. Titanium oxide was mixed in an amount of 0.01 mol% with respect to the lithium manganese composite oxide. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The positive electrode active material was obtained by pulverization.
The composition of the obtained positive electrode active material was Li _1.04 Mn _1.92 Mg _0.05 Ti _0.01 O ₄ .

[Example 2]
Manganese and magnesium carbonates were washed with water, dried, and then mixed with orthoboric acid, titanium oxide and lithium carbonate. Titanium oxide was mixed at 0.05 mol% with respect to the lithium manganese composite oxide. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The positive electrode active material was obtained by pulverization.
The composition of the obtained positive electrode active material was Li _1.03 Mn _1.89 Mg _0.05 Ti _0.05 O ₄ .

[Comparative Example 1]
Manganese and magnesium carbonates were washed with water, dried, and then mixed with orthoboric acid and lithium carbonate. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The obtained fired product was pulverized to obtain a positive electrode active material.
The composition of the obtained positive electrode active material was Li _1.04 Mn _1.93 Mg _0.05 O ₄ .

[Comparative Example 2]
A positive electrode active material was obtained in the same manner as in Comparative Example 1 except that manganese and magnesium carbonates were washed with water so as to have a predetermined composition ratio, dried, and then mixed with orthoboric acid and lithium carbonate.
The composition of the obtained positive electrode active material was Li _1.03 Mn _1.87 Mg _0.12 O ₄ .

Properties of the positive electrode active material (1) Lattice constant of the positive electrode active material Using an X-ray diffractometer (Ultima, manufactured by Rigaku Corporation), using CuKα1 as an X-ray source, a tube current of 200 mA, and a tube voltage of 40 kV, 15 to 70 The intensity in the range of ° was measured and calculated.

(2) (400) Crystallite Diameter of Positive Electrode Active Material The obtained positive electrode active material was subjected to an X-ray diffraction method. The X-ray diffractometry was performed using an X-ray diffractometer (Ultima, manufactured by Rigaku Corporation), using CuKα1 as an X-ray source, a tube current of 100 mA, and a tube voltage of 40 kV. Based on the X-ray diffraction pattern obtained by the X-ray diffraction method, the (400) crystallite diameter of the positive electrode active material was determined from the Scherrer formula represented by the above formula (1).

(3) Mn dissolution test of positive electrode active material After the obtained positive electrode active material was dried at 110 ° C. for 15 hours, LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate / diethyl carbonate = 3/7 at a concentration of 1 mol / L. The mixed electrolyte was mixed and stored at 85 ° C. for 48 hours. After removing the positive electrode active material by filtering this, the elution amount of Mn (weight of the Mn element with respect to the weight of the electrolytic solution) was measured by ICP spectroscopy. It can be said that the smaller the amount of Mn eluted, the better the suppression of gas generation during high temperature storage.

The results are shown in Table 1. In the table, “-” indicates that the corresponding item is not measured.
As is clear from Table 1, the positive electrode active material of the present invention had a lower elution amount of Mn than the positive electrode active material of Comparative Example 1, and was excellent in suppressing gas generation during high-temperature storage.

(4) Surface and internal concentrations of titanium, magnesium and boron The positive electrode active materials obtained in Example 1 and Example 2 were sputtered with an Ar beam for a certain time, and the concentration of each element was measured. A portion having a depth of 0 μm or more and 0.1 μm or less from the surface of the lithium transition metal composite oxide particles (sputter time within 1 minute) is defined as “the surface of the lithium transition metal composite oxide particles”. The portion larger than 1 μm (sputtering time from 1 minute to 20 minutes) is defined as “inside of lithium transition metal composite oxide particles”. The concentration of each element present on the surface of the lithium transition metal composite oxide particles was calculated as an average value of the sputtering time of 0 minutes and 1 minute. The concentration of each element present in the lithium transition metal composite oxide particles was calculated as an average value of the sputtering time of 5 minutes, 10 minutes, and 20 minutes.

The results are shown in Table 2.
As is apparent from Table 2, it can be seen that the positive electrode active material of the present invention has a concentration of boron present on the surface of the particles greater than the concentration of boron present inside the particles.
Moreover, it turns out that the density | concentration of the magnesium which exists in the surface of particle | grains of the positive electrode active material of this invention is larger than the density | concentration of magnesium which exists in a particle | grain inside.
Furthermore, it can be seen that in the positive electrode active material of the present invention, the concentration of titanium existing inside the particles is larger than the concentration of boron existing inside the particles.
Furthermore, it can be seen that in the positive electrode active material of the present invention, the concentration of magnesium present inside the particles is greater than the concentration of boron present inside the particles.

3. Evaluation of Positive Electrode Active Material Using each positive electrode active material obtained above, a secondary battery for test and a cylindrical battery in which the negative electrode was lithium metal were produced and evaluated as follows.

A. Evaluation using a secondary battery for test in which the negative electrode is lithium metal A secondary battery for test in which the negative electrode is lithium metal was produced as follows.
A paste was prepared by kneading 90 parts by weight of a positive 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 of polyvinylidene fluoride). Was applied to a positive electrode current collector and dried to obtain a positive electrode plate. Using the obtained positive electrode plate, a test secondary battery in which the negative electrode was lithium metal was produced.

(1) Initial discharge capacity Under the conditions of a charge potential of 4.3 V, a discharge potential of 2.85 V, and a discharge load of 0.2 C (where 1 C is a current load that completes the discharge in one hour. The same applies hereinafter) A test secondary battery in which the negative electrode was lithium metal was discharged. The discharge capacity at this time was defined as the initial discharge capacity.

B. Evaluation Using Cylindrical Battery A cylindrical battery was produced as follows.
A positive electrode plate was obtained by the same method as in the case of the test secondary battery in which the negative electrode was lithium metal. Further, a carbon material was used as the negative electrode active material, and was applied to the negative electrode current collector and dried in the same manner as in the case of the positive electrode plate to obtain a negative electrode plate. A porous propylene film was used as the separator. As the electrolytic solution, a solution in which LiPF6 was dissolved in a mixed solvent of ethylene carbonate / methyl ethyl carbonate = 3/7 (volume ratio) to a concentration of 1 mol / L was used. A positive electrode plate, a negative electrode plate, and a separator are formed into a thin sheet, wound and housed in a metal cylindrical battery case, and an electrolyte is injected into the battery case to form a cylindrical battery of a lithium ion secondary battery Got.

(1) Discharge capacity maintenance rate Charge / discharge was repeated under the conditions of a charge potential of 4.2 V, a discharge potential of 2.75 V, and a discharge load of 2 C, and the discharge capacity after 200 cycles was measured. The obtained discharge capacity value after 200 cycles was divided by the discharge capacity value after 1 cycle to determine the discharge capacity retention rate, and the cycle characteristics were evaluated.

(2) High-temperature discharge capacity retention rate At 60 ° C., charge / discharge was repeated under the conditions of a charge potential of 4.2 V, a discharge potential of 2.75 V, and a discharge load of 2 C, and the discharge capacity after 500 cycles was measured. The obtained value of the discharge capacity after 500 cycles was divided by the value of the discharge capacity after 1 cycle to obtain a high temperature discharge capacity retention rate, and the cycle characteristics were evaluated.

(3) Load capacity maintenance rate After measuring initial discharge capacity under the conditions of charge potential 4.2V, discharge potential 3.0V, discharge load 0.2C, charge potential 4.2V, discharge potential 3.0V, discharge load The load discharge capacity was measured under the condition of 3.0C. The obtained load discharge capacity value was divided by the initial discharge capacity to obtain the load capacity retention rate, and the load characteristics were evaluated.

(4) Initial average potential, average potential after 200 cycles and average potential maintenance rate Initial discharge capacity and electric energy were measured under the conditions of a charge potential of 4.2 V, a discharge potential of 2.75 V, and a discharge load of 2.0 C. The value of the obtained electric energy was divided by the initial discharge capacity to obtain the initial average potential.
Next, the discharge capacity and electric energy after 200 cycles were measured under the conditions of a charge potential of 4.2 V, a discharge potential of 2.75 V, and a discharge load of 2.0 C. The obtained electric energy value was divided by the initial discharge capacity, and the average potential after 200 cycles was determined.
The obtained average potential value after 200 cycles was divided by the initial average potential to determine the average potential maintenance rate.

(5) Initial high-temperature average potential, high-temperature average potential after 200 cycles, and high-temperature average potential potential maintenance ratio At 60 ° C., the initial discharge capacity is as follows: charge potential 4.2 V, discharge potential 2.75 V, discharge load 2.0 C. And the amount of power was measured. The value of the obtained electric energy was divided by the initial discharge capacity to obtain the initial high temperature average potential.
Next, at 60 ° C., the discharge capacity and electric energy after 200 cycles were measured under the conditions of a charge potential of 4.2 V, a discharge potential of 2.75 V, and a discharge load of 2.0 C. The value of the obtained electric energy was divided by the initial discharge capacity, and the high temperature average potential after 200 cycles was obtained.
The obtained high temperature average potential value after 200 cycles was divided by the initial high temperature average potential to determine the high temperature average potential maintenance rate.

The results are shown in Table 3. In the table, “-” indicates that the corresponding item is not measured.
As is apparent from Table 3, the positive electrode active material of the present invention is excellent in cycle characteristics, high temperature cycle characteristics, and load characteristics. Moreover, it can be seen that the initial average potential, the average potential after 200 cycles, the initial high temperature average potential, and the average potential after 200 cycles are high, and the average potential maintenance rate and the high temperature average potential maintenance rate are improved.

The positive 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 batteries for electric vehicles.

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

Explanation of symbols

1 8a site 2 32e site 3 16d site 4 binder 5 positive electrode active material 11 negative electrode 12 current collector 13 positive electrode 14 separator 20 cylindrical battery 30 coin-type battery 40 square battery

Claims (6)

A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure,
The lithium transition metal composite oxide has a general formula of Li _{1 + a} Mg _b Ti _c Mn _2-a-bc O _{4 + e} (a represents a number satisfying −0.2 ≦ a ≦ 0.2, and b is 0.8. 005 ≦ b ≦ 0.10, c represents a number satisfying 0.005 ≦ c ≦ 0.05, and e represents a number satisfying −0.5 ≦ e ≦ 0.5). Represented,
The lithium transition metal composite oxide is a particle, and the positive electrode active material for a non-aqueous electrolyte secondary battery in which the Mn / Mg molar ratio on the surface of the particle is less than (2-abc) / b . A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure,
The lithium transition metal composite oxide is a particle,
The concentration of boron present on the surface of the particles is greater than the concentration of boron present inside the particles,
The concentration of magnesium present on the surface of the particles is greater than the concentration of magnesium present inside the particles,
The concentration of titanium present inside the particles is greater than the concentration of boron present inside the particles,
The positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the concentration of magnesium present in the particles is greater than the concentration of boron present in the particles. A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure,
The lithium transition metal composite oxide is a particle and has boron at least on the surface of the particle,
A positive electrode active material for a non-aqueous electrolyte secondary battery, which is a lithium transition metal composite oxide containing magnesium and titanium. The boron content is 0.4 to 55.6% by weight based on the total of boron, titanium, and magnesium,
The magnesium content is 3.7 to 97.0% by weight based on the total of boron, titanium, and magnesium,
The positive electrode active for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the titanium content is 2.1 to 95.2 wt% with respect to the total of boron, titanium, and magnesium. material. 5. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium transition metal composite oxide has a (400) crystallite diameter of 700 to 1100 mm. A strip formed by forming a positive electrode active material layer using the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 as a positive electrode active material on both surfaces of a strip-shaped positive electrode current collector. A positive electrode;
Constructed by forming negative electrode active material layers using metallic lithium, lithium alloy, carbon material capable of occluding and releasing lithium ions, or compounds capable of occluding and releasing lithium ions as negative electrode active materials on both sides of the strip-shaped negative electrode current collector, respectively. A strip-shaped negative electrode,
A strip separator,
A spiral-type winding in which the strip-shaped positive electrode and the strip-shaped negative electrode are wound a plurality of times in a state of being laminated via the strip-shaped separator, and the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode A non-aqueous electrolyte secondary battery comprising a body.

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