JP2008010234A - Positive electrode active material and non-aqueous electrolyte battery - Google Patents

Abstract

A positive electrode active material excellent in charge / discharge cycle and a nonaqueous electrolyte battery using the same are provided.
A positive electrode mixture layer 2B contains a positive electrode active material. This positive electrode active material has a behavior in which the absorption edge peak appearing in the vicinity of 530 eV at the oxygen K absorption edge in the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method has a constant behavior. is there. By using such a positive electrode active material, reaction at the interface in the charged state can be suppressed, and battery characteristics can be improved.
[Selection] Figure 2

Description

  The present invention relates to a positive electrode active material and a non-aqueous electrolyte battery, and more particularly to a positive electrode active material mainly composed of a lithium composite oxide and a non-aqueous electrolyte battery using the same.

  With the increase in functionality and performance of portable devices, the power consumption of the devices is increasing, and the battery serving as a power source is required to have a higher capacity. In particular, a secondary battery having a high energy density is strongly demanded from the viewpoints of economy and reduction in size and weight of equipment. As typical secondary batteries, for example, lead storage batteries, alkaline storage batteries, lithium ion secondary batteries and the like are known.

  Among secondary batteries, lithium ion secondary batteries have advantages such as high output and high energy density. A lithium ion secondary battery includes a positive electrode and a negative electrode capable of reversibly inserting and removing lithium ions, and an electrolyte such as a non-aqueous electrolyte, a gel electrolyte, and a solid electrolyte.

As a positive electrode material for lithium ion secondary batteries, LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ that can intercalate and deintercalate lithium ions, or part of the metal elements of these lithium-containing transition metal compounds are substituted. The composite oxide prepared is used. LiMn ₂ O ₄ having a spinel structure is often used because it has a high energy density and a high voltage, and is being developed as an inexpensive material having a high voltage.

  Usually, in lithium ion secondary batteries, lithium cobaltate is used for the positive electrode and a carbon material is used for the negative electrode, and the operating voltage is used in the range of 4.2V to 2.5V. In the unit cell, the terminal voltage can be increased to 4.2 V largely due to excellent electrochemical stability of a non-aqueous electrolyte material or a separator.

  At present, in a lithium ion secondary battery that operates at a maximum of 4.2 V, the positive electrode active material such as lithium cobalt oxide only uses a capacity of about 60% of the theoretical capacity. Lithium ion secondary batteries are desired to have higher energy density, higher reliability, and longer life in addition to cost reduction.

  As a method for realizing high energy density, a high upper limit voltage for charging can be set. When the charging voltage is increased, more lithium (Li) is deintercalated and intercalated from the lithium composite oxide, which is the positive electrode active material, so that the capacity can be increased.

  By raising the charging voltage in this way, it is possible in principle to utilize the remaining capacity. In fact, as disclosed in Patent Document 1, for example, by increasing the voltage during charging to 4.25 V or more. It is known that high energy density can be realized.

International Publication No. 03/019713 Pamphlet

By the way, in a secondary battery with a high charging voltage, as the positive electrode active material, Li _x CoO ₂ (0 <x ≦ 1.0), Li _x NiO ₂ (0 <x ≦ 1.0) or the like has a high potential. The most promising in terms of stability and long life. Among these, the positive electrode active material mainly composed of LiCoO ₂ is a positive electrode active material exhibiting a high potential, and is expected to increase the charging voltage and the energy density. However, a secondary battery with a high charge voltage has a problem that the charge / discharge cycle life is reduced and the high-temperature characteristics are deteriorated.

In addition, lithium nickel composite oxide in which a part of nickel (Ni) of lithium nickelate represented by LiNiO ₂ or lithium nickelate is replaced with cobalt (Co) or manganese (Mn) is higher in potential than LiCoO _2. However, it is disadvantageous for increasing the energy density due to a decrease in discharge potential and a decrease in volume density compared to LiCoO ₂ .

Therefore, in order to stabilize the active material mainly composed of LiCoO ₂ , different elements such as aluminum (Al), magnesium (Mg), zirconium (Zr), and titanium (Ti) are dissolved (see Patent Document 2). ), LiMn _1/3 Co _1/3 Ni _1/3 O ₂ etc. are mixed in small amounts, or the LiCoO ₂ surface is coated with lithium manganate, lithium titanate or nickel cobalt composite oxide having a spinel structure. It has been proposed to do. (See Patent Document 3 and Patent Document 4)

JP 2004-303591 A JP 2000-164214 A JP 2002-151078 A

However, using a positive electrode active material obtained by improving a lithium composite oxide such as LiCoO ₂ , when a battery having a high charge voltage of a high charge voltage of 4.25 V or higher is produced, and charging and discharging are repeated at a high capacity There is a problem that the battery life is shortened due to capacity deterioration.

  Accordingly, an object of the present invention is to provide a positive electrode active material excellent in charge / discharge cycle characteristics and a nonaqueous electrolyte battery using the same.

For example, using an active material mainly composed of a layered compound represented by LiMeO ₂ (Me represents an element selected from Group 2 to Group 15) including LiCoO ₂ and LiNi _0.333 CoMn _0.333 O ₂ The battery energy density can be improved by charging so that the maximum charge voltage is 4.25V or higher, preferably 4.35V or higher, and more preferably 4.40V or higher in a properly designed positive / negative ratio. .

  However, when charging is performed at a high charging voltage of 4.25 V or more, the bonding force between Me-O is reduced with an increase in the amount of lithium (Li) extracted, so that at the interface between the active material and the electrolyte It is believed that the reactivity of increases. When the reactivity at the interface between the positive electrode active material and the electrolyte is increased, the transition metal component is eluted from the positive electrode and the active material is deteriorated, or the eluted metal is deposited on the negative electrode side so that lithium (Li) is occluded and It is considered that the battery characteristics are deteriorated by inhibiting the release or by accelerating the decomposition reaction of the electrolyte solution at the interface and forming a film on the surface of the positive electrode.

  Therefore, the inventors of the present application diligently studied, and by using a positive electrode active material that satisfies a predetermined change in the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method, It has been found that the reaction at the interface in the charged state can be suppressed and the charge / discharge cycle characteristics can be improved.

That is, in order to solve the above-described problems,
The first invention is
It is a positive electrode active material characterized by having at least one of the following (1) to (2).
(1) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
The background was subtracted so that the intensity of a straight line approximating a region of 525 eV or less was 0 in the entire spectrum, and the intensity of a straight line approximating a region of 560 eV to 600 eV was normalized to be 1 in the entire spectrum. About things
When the integrated intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained,
The ratio of the integrated intensity of the 4.65V charged state to the integrated intensity of the discharged state (4.65V charged state integrated intensity / discharged state integrated intensity) is 1.4 or more.
(2) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
For the background is subtracted so that the intensity of the straight line approximating the region of 525 eV or less is 0 in the entire spectrum,
When the energy value on the low energy side giving the half value of the peak top intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained as the absorption edge energy,
The value obtained by subtracting the absorption edge energy in the discharged state from the absorption edge energy in the charged state at a voltage selected from 4.45 V to 4.65 V is −0.7 eV or less.

The second invention is
A positive electrode having a positive electrode active material, a negative electrode, and an electrolyte;
The positive electrode active material is a non-aqueous electrolyte battery having at least one of the following (1) to (2).
(1) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
The background was subtracted so that the intensity of a straight line approximating a region of 525 eV or less was 0 in the entire spectrum, and the intensity of a straight line approximating a region of 560 eV to 600 eV was normalized to be 1 in the entire spectrum. About things
When the integrated intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained,
The ratio of the integrated intensity of the 4.65V charged state to the integrated intensity of the discharged state (4.65V charged state integrated intensity / discharged state integrated intensity) is 1.4 or more.
(2) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
For the background is subtracted so that the intensity of the straight line approximating the region of 525 eV or less is 0 in the entire spectrum,
When the energy value on the low energy side giving the half value of the peak top intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained as the absorption edge energy,
The value obtained by subtracting the absorption edge energy in the discharged state from the absorption edge energy in the charged state at a voltage selected from 4.45 V to 4.65 V is −0.7 eV or less.

  In the 1st invention and the 2nd invention, it is thought that the fall of the bond strength between metal-oxygen (Me-O) can be reduced, and the increase in the reactivity in the interface of a positive electrode active material and electrolyte solution is suppressed.

  According to the present invention, excellent charge / discharge cycle characteristics can be obtained.

The positive electrode active material according to one embodiment of the present invention is characterized by having at least one of the characteristics described in the following (1) to (2).
(1) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
The background was subtracted so that the intensity of a straight line approximating a region of 525 eV or less was 0 in the entire spectrum, and the intensity of a straight line approximating a region of 560 eV to 600 eV was normalized to be 1 in the entire spectrum. About things
When the integrated intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained,
The ratio of the integrated intensity of the 4.65V charged state to the integrated intensity of the discharged state (4.65V charged state integrated intensity / discharged state integrated intensity) is 1.4 or more.
(2) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
For the background is subtracted so that the intensity of the straight line approximating the region of 525 eV or less is 0 in the entire spectrum,
When the energy value on the low energy side giving the half value of the peak top intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained as the absorption edge energy,
The value obtained by subtracting the absorption edge energy in the discharged state from the absorption edge energy in the charged state at a voltage selected from 4.45 V to 4.65 V is −0.7 eV or less.

  By using a positive electrode active material that satisfies at least one of the characteristics (1) to (2) in the X-ray absorption spectrum at the oxygen K absorption edge, a nonaqueous electrolyte battery having excellent charge / discharge cycle characteristics is obtained. Can do. In addition, a nonaqueous electrolyte battery having a tendency to be excellent in high charge voltage property, high energy density property and high temperature property associated therewith can be obtained.

  In addition, it is estimated that the improvement effect mentioned above is based on the mechanism demonstrated below. That is, in a battery having a high charge voltage, the positive electrode active material generates a high electromotive force, and thus the electrolyte in contact with the positive electrode active material is in a strong oxidizing environment. As a result, it is considered that the metal component is eluted from the positive electrode active material which has become unstable due to the extraction of more lithium (Li), and the oxidative decomposition of the electrolyte occurs.

  Since the eluted metal component is reduced and deposited on the negative electrode side and covers the negative electrode surface, it is considered that the occlusion and release of lithium is impeded, and when the electrolyte is oxidized and decomposed to form a film on the positive electrode, the impedance increases. As a result, the charge / discharge cycle characteristics deteriorate.

  On the other hand, by using the positive electrode active material according to one embodiment of the present invention, a nonaqueous electrolyte battery excellent in charge / discharge cycle characteristics can be obtained. This is because the compound that does not satisfy any of (1) to (2) is compared with the compound that satisfies at least one of (1) to (2) on the surface of the positive electrode active material when charged. Changes in the 2p orbit of oxygen (O) appear. That is, since the positive electrode active material that satisfies at least one of (1) to (2) has low reactivity on the surface of the positive electrode active material, the formation of a film or the like on the surface of the active material is suppressed, While the behavior of oxygen in the active material can be confirmed, in the case of a positive electrode active material that does not satisfy any of (1) and (2), a film or the like is formed on the surface of the active material, so that oxygen in the active material Since it becomes difficult to confirm the behavior of, it is considered that the spectrum is not so different from the discharged state even if charging is performed. Therefore, by using a positive electrode active material characterized by satisfying at least one of (1) to (2), the reaction with the electrolytic solution on the positive electrode surface and the elution of metal components from the positive electrode active material are suppressed. Therefore, it is estimated that the charge / discharge cycle characteristics are improved.

  Here, a method for measuring the X-ray absorption spectrum at the oxygen K absorption edge by the X-ray absorption fine structure analysis (XAFS) method will be described.

  Use of an apparatus capable of generating soft X-rays and changing the energy of soft X-rays before and after the K absorption edge of oxygen because the oxygen K absorption edge (532 eV) exists in the soft X-ray region. It is desirable to use synchrotron radiation X-rays. The properties of (1) and (2) do not depend on the measuring device. For example, the devices of “High Energy Accelerator Research Organization, Institute for Materials Structure Science, Synchrotron Radiation Research Facility”, and “Ritsumeikan University SR Center” Can be used.

  Generally, the entire measurement system is held in a vacuum from the X-ray source to the periphery of the sample. X-rays from the X-ray source are monochromatized by a plane diffraction grating or the like with unequal engraved line spacing, and shaped using a slit or the like, and at the same time, X-rays of desired energy before and after the oxygen K absorption edge are taken out. .

  The monochromatic X-ray is irradiated onto a metal mesh such as gold (Au), and the incident X-ray intensity is measured. X-rays transmitted through the mesh are incident on a sample containing a positive electrode active material. Electrons in the 1s orbit of oxygen in the active material are excited by incident X-rays, and the intensity of Auger electrons emitted during the deexcitation is measured with a detector such as an electron multiplier. Secondary electrons generated inside the sample by Auger electrons may also be measured. Instead of selecting only Auger electrons, a method of collectively detecting photoelectrons including Auger electrons having a certain energy or more may be adopted. In that case, a negative voltage is applied between the sample and a detector such as an electron multiplier with reference to the sample. Further, instead of detecting photoelectrons emitted from the sample, alternative means such as a method of measuring a current flowing through the sample or a fluorescent X-ray from the sample can be used.

  While changing the energy of the incident X-rays before and after the oxygen K absorption edge, the intensity of the incident X-rays and electrons emitted from the sample are measured, and finally, the intensity of the electrons is divided by the intensity of the incident X-rays. Obtain a spectrum. The energy of the incident X-ray is calibrated in advance with a standard sample or the like. For example, the energy is calibrated so that the energy of the peak top of the peak generated on the lowest energy side at the oxygen K absorption edge of NiO powder is 532 eV.

  The K absorption edge of oxygen is determined as the inflection point of the raw spectrum. Usually, it is determined as a value around 530 eV. The region on the lower energy side from the determined absorption edge is regarded as the background, and the background is subtracted from the whole raw spectrum by subtracting a straight line approximating the raw spectrum from the absorption edge, for example, the region lower than 5 eV. Subtract. Furthermore, normalization may be performed in order to make the average intensity of the absorption spectrum on the higher energy side from the absorption edge uniform between samples. In the vicinity of the absorption edge, the difference in the electronic state of oxygen in the sample is sensitively reflected, and the intensity fluctuation is large. Therefore, the intensity of a straight line approximating the region on the higher energy side than such a region, for example, the region of 30 eV to 70 eV on the higher energy side from the determined absorption edge, is 1 so that it is 1 in the entire spectrum range. The spectrum can be normalized. The X-ray absorption spectrum to be analyzed is a spectrum obtained by subtracting the background from the raw spectrum, or a spectrum obtained by subtracting the background and normalizing.

  The positive electrode active material according to an embodiment of the present invention can be manufactured, for example, by the method described below. The main component of the positive electrode active material is preferably substantially lithium cobalt oxide. For example, adding at least one element selected from Group 2 to Group 15 to lithium cobaltate to replace cobalt (Co), or coating the surface layer of lithium cobaltate with a different compound The positive electrode active material having the above characteristics (1) to (2) can be obtained by improving the characteristics of lithium cobaltate.

  For example, at least a part of lithium cobaltate particles is preferably coated with a composite oxide containing lithium (Li) and containing at least one of nickel (Ni) and manganese (Mn). It is a method to do. Further, a fluorine (F) -containing compound such as lithium fluoride (LiF) or graphite fluoride, a coating treatment using aluminum lactate or ammonium phosphate as a starting material, or treatment with fluorine (F) gas may be performed. It is also possible to combine these.

  Furthermore, as a method for improving the characteristics, for example, in a positive electrode active material coated with a compound containing at least one of nickel (Ni) and (Mn), the surface layer is coated with a different compound. Although it can use suitably, it is not limited to this.

  Furthermore, in element substitution and coating treatment, the effect obtained varies depending on the raw material used and the treatment method, for example, metal oxidation mainly composed of nickel (Ni) or manganese (Mn) oxide containing lithium (Li). In the case of coating with a material, a coating material such as carbonate or hydroxide is coated on the base material with a device that applies compressive shear stress, such as a mechanochemical method, followed by heat treatment. Alternatively, by applying a heat treatment after depositing a metal hydroxide on the base material by a neutralization titration method, characteristics under a high charge voltage can be improved.

  Furthermore, even if it is another manufacturing method, if the absorption edge peak which appears in the vicinity of 530 eV of the oxygen K absorption edge of the positive electrode active material obtained by the manufacturing method shows the above (1) to (2) Applicable. In addition, when covering or element substitution is performed, the elemental ratio of cobalt (Co) is lowered, but the elemental ratio of cobalt (Co) is preferably 70% or more in at least the entire transition metal.

As an average composition of a positive electrode active material, what is represented by following General formula 1 can be used preferably.
(Chemical formula 1)
Li _{(1 + p)} Co _(1-q) M _q O _(2-y) X _z
(In the formula, M represents at least one element selected from Groups 2 to 15 excluding cobalt (Co), and X represents at least one element selected from Group 16 elements and Group 17 elements other than oxygen (O). p, q, y, and z are in the range of −0.10 ≦ p ≦ 0.10, 0 ≦ q <0.3, −0.10 ≦ y ≦ 0.20, and 0 ≦ z ≦ 0.1. Value.)

The absorption edge peak appearing in the vicinity of 530 eV of the oxygen K absorption edge of the positive electrode active material mainly composed of LiCoO _{2 and} having a molar ratio of cobalt (Co) in the transition metal of 0.7 or more is the above (1) to ( By using the positive electrode active material that exhibits at least one behavior of 2), the reaction at the interface in the charged state can be suppressed, and the battery characteristics can be improved. When the molar ratio of cobalt (Co) is less than 0.7, the average discharge voltage of the battery is lowered, and the density of the positive electrode active material is lowered, so that an improvement in energy density cannot be expected.

  In the positive electrode active material represented by Chemical Formula 1, the range of p is −0.10 ≦ p ≦ 0.10, −0.08 ≦ p ≦ 0.08 is preferable, and −0.06 ≦ p ≦ 0. 0.06 is more preferable. If the value of p is less than −0.10, the discharge capacity is reduced. If the value of p exceeds 0.10, it diffuses out of the particles, which hinders control of the basicity in the electrode manufacturing process.

The range of q is 0 ≦ q <0.3, preferably 0 ≦ q <0.20, and more preferably 0 ≦ q <0.10. This is because, if it is out of the range of 0 ≦ q <0.3, the high charge voltage property and accompanying high energy density property of LiCoO ₂ are impaired.

  The range of y is −0.10 ≦ y ≦ 0.20, preferably −0.08 ≦ y ≦ 0.18, and more preferably −0.06 ≦ y ≦ 0.16. If it is outside the range of −0.10 ≦ y ≦ 0.20, the discharge capacity tends to decrease.

The range of z is 0 ≦ z ≦ 0.1, and 0 ≦ z ≦ 0.05 is preferable. This is because, if it is outside the range of 0 ≦ z ≦ 0.1, the high charge voltage property and the accompanying high energy density property of LiCoO ₂ are impaired.

  As the positive electrode active material, those having an average composition represented by the following chemical formula 2 can be preferably used.

(Chemical formula 2)
_{Li (1 + p) Ni (} 1-qr) Mn q M r O (2-y) X z
(Wherein M is at least one element selected from Group 2 to Group 15 excluding nickel (Ni) and manganese (Mn), and X is at least one of Group 16 elements and Group 17 elements other than oxygen (O). P, q, y, r, and z are −0.10 ≦ p ≦ 0.10, 0.005 ≦ q ≦ 0.4, 0 ≦ r ≦ 0.35, −0.10 ≦. (Y ≦ 0.20, 0 ≦ z ≦ 0.1.)

  Since the compound whose average composition is represented by Chemical Formula 2 is a compound mainly composed of nickel (Ni) and manganese (Mn), the energy density associated with the high charging voltage is improved as compared with the compound represented by Chemical Formula 1. However, since the content of cobalt (Co) can be reduced, it can be produced at low cost. When a positive electrode active material having an average composition represented by Chemical Formula 2 is used, it is possible to manufacture a lithium ion battery that is cheaper and has a higher energy density than conventional lithium cobalt oxide.

  A nonaqueous electrolyte battery using a positive electrode active material according to an embodiment of the present invention will be described. FIG. 1 shows a cross-sectional structure of a first example of a nonaqueous electrolyte battery using a positive electrode active material according to an embodiment of the present invention.

  In this battery, the upper limit charging voltage is 4.25 V or more and 4.80 V or less, and more preferably 4.35 V or more and 4.65 V or less. That is, the open circuit voltage in the fully charged state is, for example, 4.25 V or more and 4.80 V or less, and more preferably 4.35 V or more and 4.65 V or less. The lower limit discharge voltage is preferably 2.00 V or more and 3.30 V or less. High energy density can be achieved by increasing the charging voltage. The positive electrode active material to be used has at least one of the above-mentioned characteristics (1) to (2).

  This battery is called a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 2 and a belt-like negative electrode 3 are wound through a separator 4 inside a substantially hollow cylindrical battery can 1. have.

  The battery can 1 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 1, a pair of insulating plates 5 and 6 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 1, a battery lid 7, a safety valve mechanism 8 and a thermal resistance element (PTC element) 9 provided inside the battery lid 7 are interposed via a gasket 10. It is attached by caulking, and the inside of the battery can 1 is sealed. The battery lid 7 is made of, for example, the same material as the battery can 1. The safety valve mechanism 8 is electrically connected to the battery lid 7 via a heat sensitive resistance element 9, and the disk plate 11 is inverted when the internal pressure of the battery becomes a certain level or more due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 7 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 9 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 10 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The wound electrode body 20 is wound around, for example, the center pin 12. A positive electrode lead 13 made of, for example, aluminum (Al) or the like is connected to the positive electrode 2 of the spirally wound electrode body 20, and a negative electrode lead 14 made of, for example, nickel (Ni) or the like is connected to the negative electrode 3. The positive electrode lead 13 is electrically connected to the battery cover 7 by being welded to the safety valve mechanism 8, and the negative electrode lead 14 is welded and electrically connected to the battery can 1.

[Positive electrode]
FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. As shown in FIG. 2, the positive electrode 2 includes, for example, a positive electrode current collector 2A having a pair of opposed surfaces, and a positive electrode mixture layer 2B provided on both surfaces of the positive electrode current collector 2A. In addition, you may make it have the area | region where the positive mix layer 2B was provided only in the single side | surface of 2 A of positive electrode collectors. The positive electrode current collector 2A is made of, for example, a metal foil such as an aluminum (Al) foil. The positive electrode mixture layer 2B includes, for example, a positive electrode active material, and may include a conductive agent such as graphite and a binder such as polyvinylidene fluoride as necessary. As the positive electrode active material, a positive electrode active material having at least one of the above-described characteristics (1) to (2) is used.

[Negative electrode]
As shown in FIG. 2, the negative electrode 3 includes, for example, a negative electrode current collector 3A having a pair of opposed surfaces, and a negative electrode mixture layer 3B provided on both surfaces of the negative electrode current collector 3A. In addition, you may make it have the area | region in which the negative mix layer 3B was provided only in the single side | surface of 3 A of negative electrode collectors. The negative electrode current collector 3A is made of a metal foil such as a copper (Cu) foil. The negative electrode mixture layer 3B includes, for example, a negative electrode active material, and may include a binder such as polyvinylidene fluoride as necessary.

  As the negative electrode active material, any material can be used as long as it is electrochemically doped and dedoped with lithium at a potential of lithium metal of 2.0 V or less. Examples include non-graphitizable carbon, artificial graphite, natural graphite, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, organic polymer compound fired bodies ( And carbonaceous materials such as phenol resin, furan resin and the like obtained by firing and carbonizing at a suitable temperature), carbon fiber, activated carbon, carbon black and the like. A metal capable of forming an alloy with lithium, an alloy thereof, or an intermetallic compound can also be used. Oxides such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, and tin oxide that dope and undope lithium with a relatively low potential, and other nitrides can also be used.

[Electrolyte]
As the electrolytic solution, a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent can be used. A nonaqueous solvent and an electrolyte salt are appropriately combined, and any nonaqueous solvent can be used as long as it is used for this type of battery. For example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4 -Methyl-1,3 dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate ester, butyrate ester, propionate ester and the like.

Any lithium salt that is an electrolyte salt can be used as long as it is used in this type of battery. For example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiCl, LiBr, etc.

[Separator]
The separator 4 is made of a porous film made of a polyolefin-based material such as polyethylene (PE) or polypropylene (PP). The separator 4 may have a structure in which two or more porous films are stacked.

  Next, the manufacturing method of the 1st example of a nonaqueous electrolyte battery is demonstrated. Hereinafter, a nonaqueous electrolyte battery manufacturing method will be described by taking a cylindrical nonaqueous electrolyte battery as an example.

  The positive electrode 2 is produced as described below. First, for example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to form a positive electrode mixture. Use slurry.

  Next, after applying this positive electrode mixture slurry to the positive electrode current collector 2A and drying the solvent, the positive electrode mixture layer 2B is formed by compression molding with a roll press or the like, and the positive electrode 2 is produced.

  The negative electrode 3 is produced as described below. First, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a negative electrode mixture slurry.

  Next, after applying this negative electrode mixture slurry to the negative electrode current collector 3A and drying the solvent, the negative electrode mixture layer 3B is formed by compression molding using a roll press or the like, and the negative electrode 3 is produced.

  Next, the positive electrode lead 13 is attached to the positive electrode current collector 2A by welding or the like, and the negative electrode lead 14 is attached to the negative electrode current collector 3A by welding or the like. Next, the positive electrode 2 and the negative electrode 3 are wound through the separator 4, and the tip of the positive electrode lead 13 is welded to the safety valve mechanism 8, and the tip of the negative electrode lead 14 is welded to the battery can 1. The rotated positive electrode 2 and negative electrode 3 are sandwiched between a pair of insulating plates 5 and 6 and stored in the battery can 1.

  Next, an electrolytic solution is injected into the battery can 1 and the separator 4 is impregnated with the electrolytic solution. Next, the battery lid 7, the safety valve mechanism 8, and the heat sensitive resistance element 9 are fixed to the opening end of the battery can 1 by caulking through the gasket 10. Thus, a nonaqueous electrolyte battery is produced.

  FIG. 3 shows the structure of a second example of the nonaqueous electrolyte battery using the positive electrode active material according to one embodiment of the present invention. As shown in FIG. 3, the nonaqueous electrolyte battery is sealed by housing the battery element 30 in an exterior material 37 made of a moisture-proof laminate film and welding the periphery of the battery element 30. The battery element 30 is provided with a positive electrode lead 32 and a negative electrode lead 33, and these leads are sandwiched between outer packaging materials 37 and pulled out to the outside. A resin piece 34 and a resin piece 35 are coated on both surfaces of the positive electrode lead 32 and the negative electrode lead 33 in order to improve the adhesion to the exterior material 37.

[Exterior material]
The packaging material 37 has, for example, a stacked structure in which an adhesive layer, a metal layer, and a surface protective layer are sequentially stacked. The adhesive layer is made of a polymer film. Examples of the material constituting the polymer film include polypropylene (PP), polyethylene (PE), unstretched polypropylene (CPP), linear low density polyethylene (LLDPE), and low density. A polyethylene (LDPE) is mentioned. The metal layer is made of a metal foil, and an example of a material constituting the metal foil is aluminum (Al). Moreover, as a material which comprises metal foil, it is also possible to use metals other than aluminum (Al). Examples of the material constituting the surface protective layer include nylon (Ny) and polyethylene terephthalate (PET). The surface on the adhesive layer side is a storage surface on the side where the battery element 30 is stored.

[Battery element]
For example, as shown in FIG. 4, the battery element 30 includes a strip-shaped negative electrode 43 provided with a gel electrolyte layer 45 on both sides, a separator 44, and a strip-shaped positive electrode 42 provided with a gel electrolyte layer 45 on both sides. The battery element 30 is a wound type battery element 30 that is formed by laminating the separator 44 and wound in the longitudinal direction.

  The positive electrode 42 includes a strip-shaped positive electrode current collector 42A and a positive electrode mixture layer 42B formed on both surfaces of the positive electrode current collector 42A. The positive electrode current collector 42A is a metal foil made of, for example, aluminum (Al). The positive electrode mixture layer 42B includes a positive electrode active material having the characteristics (1) to (2).

  One end of the positive electrode 42 in the longitudinal direction is provided with a positive electrode lead 32 connected by, for example, spot welding or ultrasonic welding. As a material of the positive electrode lead 32, for example, a metal such as aluminum can be used.

  The negative electrode 43 includes a strip-shaped negative electrode current collector 43A and a negative electrode mixture layer 43B formed on both surfaces of the negative electrode current collector 43A. The negative electrode current collector 43A is made of, for example, a metal foil such as a copper (Cu) foil, a nickel foil, or a stainless steel foil.

  Similarly to the positive electrode 42, the negative electrode lead 33 connected by, for example, spot welding or ultrasonic welding is also provided at one end portion of the negative electrode 43 in the longitudinal direction. As a material of the negative electrode lead 33, for example, copper (Cu), nickel (Ni) or the like can be used.

  Since things other than the gel electrolyte layer 45 are the same as those in the first example described above, the gel electrolyte layer 45 will be described below.

  The gel electrolyte layer 45 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte layer 45 is preferable because it can obtain high ionic conductivity and prevent battery leakage. The configuration of the electrolytic solution (that is, the liquid solvent, the electrolyte salt, and the additive) is the same as that in the first embodiment.

  As the matrix of the gel electrolyte layer 45, various polymers can be used as long as they absorb the electrolyte and gel. For example, fluorine-based polymers such as poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and cross-linked products thereof, and poly (acrylonitrile) Can be used. In particular, it is desirable to use a fluorine-based polymer from the viewpoint of redox stability. By containing an electrolyte salt, ionic conductivity is imparted.

  Next, a manufacturing method of a second example of the nonaqueous electrolyte battery using the positive electrode active material according to the embodiment of the present invention will be described. First, a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent is applied to each of the positive electrode 42 and the negative electrode 43, and the mixed solvent is volatilized to form the gel electrolyte layer 45. In addition, the positive electrode lead 32 is attached to the end of the positive electrode current collector in advance by welding, and the negative electrode lead 33 is attached to the end of the negative electrode current collector 43A by welding.

  Next, the positive electrode 42 and the negative electrode 43 on which the gel electrolyte layer 45 is formed are laminated through a separator 44 to form a laminated body, and then the laminated body is wound in the longitudinal direction to form a wound battery element. 30 is formed.

  Next, a recess 36 is formed by deep-drawing an exterior material 37 made of a laminate film, the battery element 30 is inserted into the recess 36, and an unprocessed portion of the exterior material 37 is folded back to the upper portion of the recess 36. The outer peripheral part of is thermally welded and sealed. Thus, a nonaqueous electrolyte battery is produced.

<Example 1>
First, lithium carbonate (Li ₂ CO ₃ ), nickel hydroxide (Ni (OH) ₂ ), and manganese carbonate (MnCO ₃ ) are mixed with Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = 1.08: 1. : 1 (corresponding to Li _1.08 Ni _0.5 Mn _0.5 O ₂ ), and weighed to a mean particle size of 1 μm or less by a wet method using a ball mill apparatus, and then dried under reduced pressure at 70 ° C.

Next, the obtained powder was weighed so as to be 10 parts by weight as Li _1.08 Ni _0.5 Mn _0.5 O ₂ , and this powder and lithium cobalt oxide (LiCoO ₂ ) having an average particle diameter of 13 μm (measured by a laser scattering method). 100 parts by weight were mixed. This mixed powder was treated with a mechanochemical apparatus for 1 hour to deposit Li ₂ CO ₃ , Ni (OH) ₂ , and MnCO ₃ on the surface of lithium cobalt oxide (LiCoO ₂ ).

  Next, this calcined precursor was heated at 3 ° C. per minute using an electric furnace, kept at 800 ° C. for 3 hours, and then gradually cooled. Thus, the positive electrode active material of Example 1 was produced.

In addition, when the positive electrode active material powder of Example 1 was analyzed by the atomic absorption spectrum, the composition of LiCo _0.908 Ni _0.046 Mn _0.046 O ₂ was confirmed. Moreover, when the particle size was measured by the laser diffraction method, the average particle size was 13.5 μm. Furthermore, when the powder of Example 1 was observed by SEM / EDX (Scanning Electron Microscopy / Energy Dispersive X-ray spectrometer), nickel manganese having a particle size of about 0.1 μm to 5 μm was formed on the surface of lithium cobaltate (LiCoO ₂ ). It was observed that the metal compound was deposited and that nickel (Ni) and manganese (Mn) were present almost uniformly over the entire surface.

<Example 2>
A positive electrode active material of Example 2 was produced in the same manner as Example 1 except that lithium composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was used instead of lithium cobalt oxide (LiCoO ₂ ). When the positive electrode active material powder of Example 2 was analyzed by atomic absorption spectrum, the composition of LiCo _0.089 Ni _0.046 Mn _0.046 Al _0.09 Mg _0.009 O ₂ was confirmed.

<Example 3>
Lithium carbonate (Li ₂ CO ₃ ), nickel hydroxide (Ni (OH) ₂ ), manganese carbonate (MnCO ₃ ), Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = 1.08: 1 .6: A positive electrode active material of Example 3 was produced in the same manner as in Example 1, except that the molar ratio was 0.4 (Li _1.08 Ni _0.8 Mn _0.2 O ₂ equivalent). In addition, when the positive electrode active material powder of Example 3 was analyzed by the atomic absorption spectrum, the composition of LiCo _0.908 Ni _0.069 Mn _0.023 O ₂ was confirmed.

<Example 4>
Lithium carbonate (Li ₂ CO ₃ ), nickel hydroxide (Ni (OH) ₂ ) and manganese carbonate (MnCO ₃ ) are mixed with Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = 1.08: 1: 1. It was weighed so as to have a molar ratio (equivalent to Li _1.08 Ni _0.5 Mn _0.5 O ₂ ), pulverized to a mean particle size of 1 μm or less with a ball mill device, and then dried under reduced pressure at 70 ° C.

Next, 50 parts by weight of the obtained powder was coated on 100 parts by weight of lithium cobaltate (average chemical composition analysis value: Li _1.03 CoO ₂ ) in the same manner as in Example 1 to obtain the positive electrode of Example 4. An active material was prepared. In addition, when the positive electrode active material powder of Example 4 was analyzed by atomic absorption spectrum, the composition of LiCo _0.662 Ni _0.169 Mn _0.169 O ₂ was confirmed.

<Example 5>
First, 1000 parts by weight of lithium composite oxide (average chemical composition analysis value: Li _1.03 Co _0.98 Al _0.01 Mg _0.01 O ₂ ) having an average particle diameter of 13 μm (measured by a laser scattering method) is added to 2000 parts by weight of pure water at 50 ° C. A solution was prepared by stirring and dispersing for 1 hour.

Next, with respect to this solution, 130 parts by weight of commercially available nickel sulfate (Ni ₂ SO ₄ .6H ₂ O) and 85 parts by weight of manganese sulfate (MnSO ₄ .H ₂ O) were added to 1000 parts by weight of pure water. At the same time, 450 parts by weight of the solution dissolved in the solution was added at 7.5 parts by weight / minute, and at the same time, diluted NH ₃ water diluted to 4% NH ₃ by diluting the commercially available reagent 25% NH ₃ at 1.5 parts by weight / minute. Added. Further, a commercially available reagent 25% NaOH aqueous solution was added so that the pH was 11.0, and stirring and dispersion were continued for 1 hour, followed by cooling.

  Next, the dispersion was washed by filtration and dried at 120 ° C. The precursor sample thus obtained has hydroxides formed on the surface.

Next, in order to adjust the amount of lithium, 1000 parts by weight of the precursor sample was uniformly mixed and dried with a commercially available reagent LiOH.H ₂ O to obtain a calcined precursor. Next, the calcined precursor was heated to 800 ° C. at 5 ° C. per minute using an electric furnace, kept at 800 ° C. for 5 hours, and then gradually cooled. Thus, the positive electrode active material of Example 5 was produced. In addition, when the positive electrode active material powder of Example 5 was analyzed by atomic absorption spectrum, the composition of LiCo _0.94 Ni _0.02 Mn _0.02 Al _0.01 Mg _{0 · 01} O ₂ was confirmed.

<Example 6>
Lithium fluoride (LiF) powder 10 mol% and lithium cobalt oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) 90 mol% were treated with a mechanofusion apparatus for 1 hour, and lithium fluoride (LiF) was coated on the lithium cobalt oxide surface. I wore it. The calcined precursor was heated at 3 ° C. per minute, held at 700 ° C. for 3 hours, and then slowly cooled to produce the positive electrode active material of Example 6. In addition, when the positive electrode active material powder of Example 6 was analyzed by atomic absorption spectrum, the composition of Li _1.1 Co _0.98 Al _0.01 Mg _0.01 O ₂ F _0.1 was confirmed.

<Example 7>
Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = 1.08: 1: 1 (Li _1.08 Ni _0.5 Mn _0.5 O ₂ equivalent) is weighed so that the molar ratio is 1 μm or less with a ball mill device. After being pulverized until dried, it was dried under reduced pressure at 70 ° C. In the same manner as in Example 1, 8.5 parts by weight of the obtained powder and 1.5 parts by weight of lithium fluoride (LiF) powder were added to 100 parts by weight of a lithium composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ). On the other hand, the coating process was performed and the positive electrode active material of Example 7 was produced. In addition, when the positive electrode active material powder of Example 7 was analyzed by the atomic absorption spectrum, the composition of Li _1.06 Co _0.90 Ni _0.05 Mn _0.05 Al _0.01 Mg _0.01 O ₂ F _0.6 was confirmed.

<Example 8>
In the same manner as in Example 1, the positive electrode active material of Example 8 was produced.

<Example 9>
In the same manner as in Example 1, a positive electrode active material of Example 9 was produced.

<Example 10>
In the same manner as in Example 2, the positive electrode active material of Example 10 was produced.

<Example 11>
In the same manner as in Example 2, the positive electrode active material of Example 11 was produced.

<Example 12>
Using a commercially available nickel nitrate, cobalt nitrate, and manganese nitrate as an aqueous solution, the molar ratio of nickel (Ni), cobalt (Co), and manganese (Mn) (Ni: Co: Mn) is 0.50: 0.20: It mixed so that it might be set to 0.30, and ammonia water was dripped, stirring fully, and the composite hydroxide was obtained. Next, this was mixed with lithium hydroxide, calcined at 900 ° C. for 10 hours in an oxygen stream, and then pulverized to produce a positive electrode active material of Example 12.

In addition, when the positive electrode active material powder of Example 12 was analyzed by atomic absorption spectrum, the composition of LiNi _0.50 Co _0.20 Mn _0.30 O ₂ was confirmed. Further, when the particle size was measured by a laser diffraction method, the average particle size was 13 μm. Furthermore, when X-ray diffraction measurement of this powder was performed, the pattern obtained was similar to the pattern of LiNiO ₂ in 09-0063 of ICDD, and formed a layered rock salt structure similar to LiNiO ₂ . Was confirmed. Furthermore, when the powder was observed by SEM (Scanning Electron Microscopy), spherical particles in which primary particles of 0.1 μm to 5 μm were aggregated were observed.

<Comparative Example 1>
As Comparative Example 1, a lithium composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was used.

<Comparative example 2>
As Comparative Example 2, a lithium composite oxide (LiNi _0.045 Co _0.91 Mn _0.045 O ₂ ) was used.

<Comparative Example 3>
Commercially available nickel hydroxide, cobalt hydroxide, and manganese carbonate with a molar ratio (Ni: Co: Mn) of nickel (Ni), cobalt (Co), and manganese (Mn) of 0.50: 0.20: 0.30 After mixing with a ball mill, the mixture was further mixed with lithium hydroxide, calcined at 700 ° C. for 10 hours in an air stream, and pulverized to prepare a positive electrode active material of Comparative Example 3.

When the obtained positive electrode active material powder was analyzed by atomic absorption analysis, the composition of LiNi _0.50 Co _0.20 Mn _0.30 O ₂ was confirmed. Further, when the particle size was measured by a laser diffraction method, the average particle size was 8 μm. Moreover, when X-ray diffraction measurement of this powder was performed, the obtained pattern was similar to the pattern of LiNiO ₂ in 09-0063 of ICDD, and formed the same layered rock salt structure as LiNiO ₂ . Things were confirmed. Further, when the powder was observed by SEM, spherical particles in which primary particles of 0.1 to 5 μm were aggregated were observed.

<Comparative Example 4>
Lithium composite oxide (LiCoO ₂ ) was used as the positive electrode active material of Comparative Example 4.

<Comparative Example 5>
Lithium composite oxide (LiCoO ₂ ) was used as the positive electrode active material of Comparative Example 5.

<Comparative Example 6>
Lithium composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was used as the positive electrode active material of Comparative Example 6.

<Comparative Example 7>
Lithium composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was used as the positive electrode active material of Comparative Example 7.

<Comparative Example 8>
A positive electrode active material of Comparative Example 8 was produced in the same manner as in Example 1 except that the calcined precursor was heated at 3 ° C. per minute, kept at 950 ° C. for 24 hours and then gradually cooled. When the positive electrode active material powder of Comparative Example 8 was analyzed by atomic absorption spectrum, the composition of LiCo _0.908 Ni _0.046 Mn _0.046 O ₂ was confirmed.

  Table 1 shows a summary of the base material, the covering material, and the average composition of the positive electrode active materials of Examples 1 to 12 and Comparative Examples 1 to 8 produced as described above.

  Next, using the positive electrode active materials of Examples 1 to 12 and Comparative Examples 1 to 8, cylindrical batteries were produced as described below.

  First, 86% by weight of the positive electrode active material, 10% by weight of graphite as a conductive agent, and 4% by weight of polyvinylidene fluoride as a binder were mixed, and N-methyl-2-pyrrolidone (NMP) as a solvent was mixed. ) To obtain a positive electrode mixture slurry.

  This positive electrode mixture slurry was uniformly applied on both sides of a 20 μm-thick strip-shaped aluminum (Al) foil, dried, and then compressed by a roller press to obtain a strip-shaped positive electrode. At this time, the voids in the electrode were adjusted so that the volume ratio was 26%.

  Next, as a negative electrode, 10% by weight of polyvinylidene fluoride (PVdF) was mixed with 90% by weight of powdered artificial graphite and dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a negative electrode mixture slurry. This negative electrode mixture slurry was uniformly applied to both surfaces of a 10 μm thick copper (Cu) foil, dried, and then compressed with a roller press to obtain a belt-like negative electrode.

  Next, after producing a positive electrode and a negative electrode, a porous polyolefin film is used as a separator, and this separator, the positive electrode and the negative electrode are laminated in the order of the negative electrode, the separator, the positive electrode, and the separator, and then wound in a spiral shape. As a result, a spiral wound electrode body was produced.

  Next, this wound electrode body was housed in a nickel-plated iron battery can, and insulating plates were disposed on both upper and lower surfaces of the wound electrode body. An aluminum positive electrode lead was led out from the positive electrode current collector and welded to a protrusion of a safety valve in which electrical continuity with the battery lid was ensured. A nickel negative electrode lead was led out from the negative electrode current collector and welded to the bottom of the battery can.

Next, after injecting the electrolyte into the battery can in which the electrode body is incorporated, the safety can, the PTC element, and the battery lid are fixed by caulking the battery can through an insulating sealing gasket, and the outer diameter is A cylindrical battery having a height of 18 mm and a height of 65 mm was produced. The electrolyte solution was prepared by dissolving LiPF ₆ in a mixed solution having a volume mixing ratio of ethylene carbonate and diethyl carbonate of 1: 1 so as to have a concentration of 1 mol / dm ³ .

  Next, regarding the discharge state of the positive electrode active material of Example 1 to Example 12 and Comparative Example 1 to Comparative Example 9, 4.45V charge state and 4.65V charge state (each charge voltage of the positive electrode in the XAFS measurement is Li potential) The X-ray absorption spectrum at the oxygen K absorption edge was measured by XAFS measurement. XAFS measurements were performed at a synchrotron radiation facility. The sample is introduced into the measuring apparatus in an inert gas atmosphere so as not to be exposed to the air, or in a short time of 1 to 2 minutes so as to suppress the surface alteration as much as possible even when exposed to the air. I tried to do it. The energy of the incident X-ray was calibrated so that the energy at the peak top of the peak at the lowest energy side at the oxygen K absorption edge of the NiO powder was 532 eV.

  The positive electrode active material in the discharged state, 4.45 V charged state, and 4.65 V charged state has a dew point of − to prevent the sample from being altered by moisture after charging the prepared battery to a predetermined charging voltage. It was obtained by disassembling in a dry room at 50 ° C. or lower, taking out the positive electrode, washing the salt or solvent adhering to the surface with dimethyl carbonate (DMC), and drying.

  In the X-ray absorption spectrum obtained by XAFS measurement, the background is subtracted so that the intensity of the straight line approximating the region of 525 eV or less is 0 in the whole spectrum, and the intensity of the straight line approximating the region of 560 eV to 600 eV is the whole spectrum. The analysis target was standardized so as to be 1.

  Next, an integrated intensity was calculated by integrating the absorption peak region (526 eV to 534 eV) appearing in the vicinity of 530 eV of the X-ray absorption spectrum at the oxygen K absorption edge in the discharge state. The integrated intensity was calculated for the discharged state and the 4.65V charged state. Next, the integral intensity ratio = (“4.65 V integral intensity” / “discharge state integral intensity”) was determined.

  In addition, a sample that was not normalized by subtracting the background so that the intensity of a straight line approximating a region of 525 eV or less was 0 in the entire spectrum was also analyzed.

  In this X-ray absorption spectrum, it is an energy value giving a half value of the peak top intensity of the absorption edge peak, and the energy at the low energy side is taken as the absorption edge energy ("4.44V absorption edge energy in the charged state"- The value of “absorption edge energy in the discharge state”) and the value of “(absorption edge energy in the 4.65 V charge state) −“ absorption edge energy in the discharge state ”) were obtained as the absorption edge change.

Using the positive electrode active materials of Evaluation Examples 1 to 12 and Comparative Examples 1 to 8, the batteries produced in the same manner were measured for initial capacity and capacity retention rate.

Initial capacity measurement The initial capacity is charged at a predetermined voltage (4.20 V, 4.30 V, 4.35 V, 4.40 V, 4.50 V, 4.60 V) at a constant current of 45 mA at an environmental temperature of 45 ° C. At that time, switching to constant voltage charging was performed until the total charging time reached 2.5 hours, after which discharging was performed at a constant current of 800 mA and a final voltage of 3.0 V, and measurement was performed.

Measurement of Capacity Maintenance Rate Charging / discharging was repeated under the same conditions as in the initial capacity measurement, and the discharge capacity at the 200th cycle was measured to determine the capacity maintenance rate relative to the initial capacity.

  Table 2 shows the integrated intensity ratio, the absorption edge change, the initial capacity, and the capacity retention ratio for Examples 1 to 12 and Comparative Examples 1 to 8.

  FIG. 5 shows an X-ray absorption spectrum at the oxygen K absorption edge of the positive electrode active material of Example 1 in the discharged state, 4.25 V charged state, 4.45 V charged state, and 4.65 V charged state. FIG. 6 shows an X-ray absorption spectrum at the oxygen K absorption edge of the positive electrode active material of Example 7 in the discharged state, 4.25 V charged state, 4.45 V charged state, and 4.65 V charged state. FIG. 7 shows an X-ray absorption spectrum at the oxygen K absorption edge of the positive electrode active material of Comparative Example 1 in the discharged state, 4.25 V charged state, 4.45 V charged state, and 4.65 V charged state.

  As shown in Table 2, according to Examples 1 to 12 and Comparative Examples 1 to 8, compared with Comparative Examples 1 to 8 that do not have the characteristics of (1) and (2), the temperature is high. The capacity maintenance rate was high. That is, it was found that a battery using a positive electrode active material having at least one of the characteristics (1) and (2) can obtain excellent charge / discharge cycle characteristics even at high temperatures.

  Further, according to a comparison between Example 1 and Comparative Example 8, the positive electrode active material has the same average composition as shown in Table 1, but has the characteristics of (1) and (2). In Example 1, the capacity retention rate was improved. That is, a battery using a positive electrode active material having at least one characteristic of (1) and (2), even if having the same average composition, has excellent charge / discharge cycle characteristics even at high temperatures. I found out that

  Further, according to FIGS. 5 to 7, in Example 1 and Example 7, the change of 2p orbit of oxygen (O) on the surface of the positive electrode active material when charging was performed, and the surface of the positive electrode active material Since the reactivity at the surface of the active material is small, the formation of a film or the like on the surface of the active material is suppressed, and the behavior of oxygen in the active material can be confirmed. Since it becomes difficult to confirm the behavior of oxygen (O) in the active material due to the formation of a film or the like, it is considered that the spectrum does not differ much from the discharged state even when charged. Therefore, by using a positive electrode active material characterized by satisfying at least one of (1) to (2), the reaction with the electrolytic solution on the positive electrode surface and the elution of metal components from the positive electrode active material are suppressed. Therefore, it is estimated that the charge / discharge cycle characteristics are improved.

  The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, the shape of the battery is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, a button shape, and a laminate seal shape can be used. Further, for example, the electrode body may be manufactured by a lamination method in which a positive electrode, a negative electrode, and a separator are sequentially laminated.

  Furthermore, for example, the method for manufacturing the positive electrode and the negative electrode is not limited to the above-described example. For example, a method in which a known binder or the like is added to the material and heated to apply, the material alone or a conductive material, and further mixed with the binder and subjected to a treatment such as molding, and then on the current collector However, the present invention is not limited to this method. More specifically, it can be prepared by forming a slurry mixed with a binder, an organic solvent, and the like, and then applying and drying on a current collector. Alternatively, regardless of the presence or absence of the binder, it is possible to produce an electrode having a high degree by performing pressure molding while applying heat to the active material.

  Furthermore, for example, as a battery manufacturing method, a manufacturing method of winding around a core via a separator between a positive electrode and a negative electrode, a stacking method of sequentially stacking an electrode and a separator, or the like is taken. This is also effective when a winding method is adopted when a rectangular battery is produced.

  In the first example of the battery, a nonaqueous electrolyte battery having an electrolyte as an electrolyte has been described, and in the second example of the battery, a nonaqueous electrolyte battery having a gel electrolyte as an electrolyte has been described, but the present invention is not limited thereto. It is not a thing. For example, a solid electrolyte containing an electrolyte salt can be used as the electrolyte. As the solid electrolyte, any inorganic solid electrolyte or polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. The polymer compound is an ether polymer such as poly (ethylene oxide) or a crosslinked product thereof, poly (methacrylate) ester, or acrylate. Etc. can be used singly or in a molecule or in a mixture.

It is a schematic sectional drawing of the nonaqueous electrolyte battery using the positive electrode active material by one Embodiment of this invention. FIG. 2 is an enlarged sectional view of a part of a wound electrode body shown in FIG. 1. It is the schematic which shows the structure of the nonaqueous electrolyte battery using the positive electrode active material by one Embodiment of this invention. FIG. 4 is an enlarged cross section of a part of the battery element shown in FIG. 3. 2 is an X-ray absorption spectrum at an oxygen K absorption edge of the positive electrode active material of Example 1. FIG. 7 is an X-ray absorption spectrum at an oxygen K absorption edge of the positive electrode active material of Example 7. 4 is an X-ray absorption spectrum at an oxygen K absorption edge of the positive electrode active material of Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery can 2 ... Positive electrode 2A ... Positive electrode collector 2B ... Positive electrode mixture layer 3A ... Negative electrode collector 3B ... Negative electrode mixture layer 3 ... Negative electrode 4. .. Separator 5, 6 ... Insulating plate 7 ... Battery cover 8 ... Safety valve mechanism 9 ... Heat sensitive resistance element 10 ... Gasket 11 ... Disc plate 12 ... Center pin 13 .. Positive electrode lead 14 ... Negative electrode lead 20 ... Winding electrode body 30 ... Battery element 32 ... Positive electrode lead 33 ... Negative electrode lead 34, 35 ... Resin piece 35 ... Negative electrode lead 36 ... Recess 37 ... Exterior material 42 ... Positive electrode 42A ... Positive electrode current collector 42B ... Positive electrode mixture layer 43 ... Negative electrode 43A ... Negative electrode current collector 43B ... Negative electrode Mixture layer 44 ... Separator 45 ... Gel electrolyte layer

Claims (7)

A positive electrode active material having at least one of the following (1) to (2).
(1) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
The background was subtracted so that the intensity of a straight line approximating a region of 525 eV or less was 0 in the entire spectrum, and the intensity of a straight line approximating a region of 560 eV to 600 eV was normalized to be 1 in the entire spectrum. About things
When the integrated intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained,
The ratio of the integrated intensity of the 4.65V charged state to the integrated intensity of the discharged state (4.65V charged state integrated intensity / discharged state integrated intensity) is 1.4 or more.
(2) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
For the background is subtracted so that the intensity of the straight line approximating the region of 525 eV or less is 0 in the entire spectrum,
When the energy value on the low energy side giving the half value of the peak top intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained as the absorption edge energy,
The value obtained by subtracting the absorption edge energy in the discharged state from the absorption edge energy in the charged state at a voltage selected from 4.45 V to 4.65 V is −0.7 eV or less. 2. The positive electrode active material according to claim 1, wherein the average composition is represented by Chemical Formula 1. 3.
(Chemical formula 1)
Li _{(1 + p)} Co _(1-q) M _q O _(2-y) X _z
(In the formula, M represents at least one element selected from Groups 2 to 15 excluding cobalt (Co), and X represents at least one element selected from Group 16 elements and Group 17 elements other than oxygen (O). p, q, y, and z are in the range of −0.10 ≦ p ≦ 0.10, 0 ≦ q <0.3, −0.10 ≦ y ≦ 0.20, and 0 ≦ z ≦ 0.1. Value.) The positive electrode active material according to claim 1, wherein the average composition is represented by Chemical Formula 2.
(Chemical formula 2)
_{Li (1 + p) Ni (} 1-qr) Mn q M r O (2-y) X z
(Wherein M is at least one element selected from Groups 2 to 15 excluding nickel (Ni) and manganese (Mn), and X is at least one of Group 16 elements and Group 17 elements other than oxygen (O). P, q, r, y, and z are −0.10 ≦ p ≦ 0.10, 0.005 ≦ q ≦ 0.4, 0 ≦ r ≦ 0.35, and −0.10 ≦. (Y ≦ 0.20, 0 ≦ z ≦ 0.1.) A positive electrode having a positive electrode active material, a negative electrode, and an electrolyte;
The positive electrode active material has at least one or more of the following (1) to (2).
(1) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
The background was subtracted so that the intensity of a straight line approximating a region of 525 eV or less was 0 in the entire spectrum, and the intensity of a straight line approximating a region of 560 eV to 600 eV was normalized to be 1 in the entire spectrum. About things
When the integrated intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained,
The ratio of the integrated intensity of the 4.65V charged state to the integrated intensity of the discharged state (4.65V charged state integrated intensity / discharged state integrated intensity) is 1.4 or more.
(2) In the X-ray absorption spectrum at the oxygen K absorption edge measured by the X-ray absorption fine structure analysis (XAFS) method,
For the background is subtracted so that the intensity of the straight line approximating the region of 525 eV or less is 0 in the entire spectrum,
When the energy value on the low energy side giving the half value of the peak top intensity of the absorption edge peak in the range of 526 eV to 534 eV is obtained as the absorption edge energy,
The value obtained by subtracting the absorption edge energy in the discharged state from the absorption edge energy in the charged state at a voltage selected from 4.45 V to 4.65 V is −0.7 eV or less. The positive electrode active material is
The non-aqueous electrolyte battery according to claim 4, wherein the average composition is represented by chemical formula 1.
(Chemical formula 1)
Li _{(1 + p)} Co _(1-q) M _q O _(2-y) X _z
(In the formula, M represents at least one element selected from Groups 2 to 15 excluding cobalt (Co), and X represents at least one element selected from Group 16 elements and Group 17 elements other than oxygen (O). p, q, y, and z are in the range of −0.10 ≦ p ≦ 0.10, 0 ≦ q <0.3, −0.10 ≦ y ≦ 0.20, and 0 ≦ z ≦ 0.1. Value.) The positive electrode active material is
The non-aqueous electrolyte battery according to claim 4, wherein the average composition is represented by chemical formula 2.
(Chemical formula 2)
_{Li (1 + p) Ni (} 1-qr) Mn q M r O (2-y) X z
(Wherein M is at least one element selected from Groups 2 to 15 excluding nickel (Ni) and manganese (Mn), and X is at least one of Group 16 elements and Group 17 elements other than oxygen (O). P, q, r, y, and z are −0.10 ≦ p ≦ 0.10, 0.005 ≦ q ≦ 0.4, 0 ≦ r ≦ 0.35, and −0.10 ≦. (Y ≦ 0.20, 0 ≦ z ≦ 0.1.) The non-aqueous electrolyte battery according to claim 4, wherein an open circuit voltage in a fully charged state is 4.25 V or more and 4.65 V or less.

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