JP6077206B2 - ELECTRODE MATERIAL, ITS MANUFACTURING METHOD, ELECTRODE, LITHIUM ION BATTERY - Google Patents

Description

  The present invention relates to an electrode material, a manufacturing method thereof, an electrode, and a lithium ion battery, and particularly relates to a technology of a lithium ion battery capable of realizing stable charge / discharge cycle characteristics and high stability.

In recent years, the development of clean energy has been active all over the world, and among them, it is used in some electric vehicles, portable electronic devices, UPS (uninterruptible power supply) etc. as high safety and low environmental load. The secondary battery is positioned as one of the key to realizing a clean energy society.
As typical secondary batteries currently used, for example, lead storage batteries, alkaline storage batteries, lithium ion batteries, and the like are known. In particular, lithium ion batteries are reduced in size, weight, and capacity. Since it has excellent characteristics such as high output and high energy density, it has been studied as a high output power source for electric tools and electric tools.

LiCoO ₂ and LiMnO ₂ are generally used as positive electrode active materials for lithium ion batteries that are currently in practical use, but Co is unevenly distributed on the earth and is a rare resource, so it was used in large quantities. In some cases, there is a problem that the product cost is high and stable supply is difficult. Therefore, as a positive electrode active material replacing LiCoO ₂ , spinel LiMn ₂ O ₄ , ternary LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , lithium ferrate (LiFeO ₂ ), olivine structure Research and development of positive electrode active materials such as lithium iron phosphate (LiFePO ₄ ) has been actively promoted.
Among these, LiFePO ₄ having an olivine structure has attracted attention as a positive electrode material that is expected to be stably supplied not only in safety but also in terms of resources and costs.
The positive electrode material having an olivine structure typified by LiFePO ₄ contains phosphorus as a constituent element and is strongly covalently bonded to oxygen, and therefore releases oxygen at a higher temperature than a positive electrode material such as LiCoO _2. In addition, there is no risk of ignition due to oxidative decomposition of the electrolyte, and the material is excellent in safety.

However, the olivine-structured LiFePO ₄ having such advantages also has a problem of low electron conductivity. This low electron conductivity is considered to be the slow diffusion of lithium ions inside the active material derived from the olivine structure and the low electronic conductivity.
Therefore, as an electrode material with improved electron conductivity, for example, Li _x A _y D _z PO ₄ (where A is one or two selected from the group of Co, Mn, Ni, Fe, Cu, Cr) Species or more, D is one or more selected from the group of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, rare earth elements, 0 <X <2, 0 <y <1, 0 ≦ z <1.5), a plurality of primary particles of the electrode active material are aggregated to form secondary particles, and electron conductivity is provided between these primary particles. An electrode material in which carbon is interposed as a substance and the surface of the electrode active material is coated with a carbonaceous film and a method for producing the same have been proposed (for example, see Patent Documents 1 to 4).
These electrode materials are sprayed with a slurry containing an electrode active material or a precursor of an electrode active material and an organic compound, and dried to produce a granulated body. The granulated body is 500 ° C. or higher and 1000 ° C. or lower. It can be obtained by heat treatment in a non-oxidizing atmosphere.

JP 2004-014340 A JP 2004-014341 A JP 2001-015111 A JP 2010-161038 A

However, a plurality of primary particles of the electrode active material composed of Li _x A _y D _z PO ₄ described above are aggregated to form secondary particles, and carbon is interposed between the primary particles, and further, the electrode active material In order to give sufficient electron conductivity, it is necessary to improve the electron conductivity of the coated carbonaceous film. The electron conductivity of the carbonaceous film is not sufficient, and therefore, the desorption / insertion of Li does not work well, and it is difficult to realize stable charge / discharge cycle characteristics and high stability. .

  The present invention has been made to solve the above-described problems, and provides an electrode material capable of realizing stable charge / discharge cycle characteristics and high stability, a manufacturing method thereof, an electrode, and a lithium ion battery. For the purpose.

As a result of intensive studies to solve the above problems, the present inventors have found that lithium cobaltate, lithium nickelate, lithium manganate, lithium titanate, Li _x A _y D _z PO ₄ (where A is Co , Mn, Ni, Fe, Cu, Cr, one or more selected from the group, D is Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc , Y, one or more selected from the group of rare earth elements, and one selected from the group of 0 <x <2, 0 <y <1, 0 ≦ z <1.5) as a main component When the Raman spectrum analysis of the electrode material formed by coating the surface of the electrode active material to be covered with a carbonaceous film is performed, the peak intensity (I ₁₃₆₀ ) of the spectrum in the wavelength band of 1360 ± 50 cm ⁻¹ of this Raman spectrum analysis 1580 ± 50 If for spectral peak intensity in the wavelength band of the m ^-1 _{(I 1580)} R value is the ratio _{(I 1360} / _{I 1580)} of 0.65 or more and 1.00 or less, and coating the surface of electrode active material The electronic conductivity of the carbonaceous film is improved, and therefore Li desorption / insertion works well. As a result, it has been found that stable charge / discharge cycle characteristics and high stability are possible. It came to be completed.

That is, in the electrode material of the present invention, a plurality of primary particles of an electrode active material made of LiFePO ₄ are aggregated to form secondary particles, and carbon is interposed between these primary particles. An electrode material in which the surface of a primary particle is coated with a carbonaceous film, and a spectrum in a wavelength band of 1580 ± 50 cm ⁻¹ of a peak intensity (I ₁₃₆₀ ) of a spectrum in a wavelength band of 1360 ± 50 cm ⁻¹ of Raman spectrum analysis. of peak intensity _{(I 1580)} R value is the ratio _{(I 1360} / _{I 1580)} is 0.65 or more and 1.00 or less, and a peak derived from carbons in the wavelength band of ^{1100cm -1 ~1300cm} -1 It is characterized in that only exists.

The Raman spectral analysis peaks in the spectrum are present in a wavelength band of ^{1000cm -1 ~1500cm} -1 of the half width Δν of a peak of the spectrum is preferably 300 cm ^-1 or less.
The powder resistance is preferably 200 Ω · cm or less.

The method for producing an electrode material of the present invention comprises a slurry containing an electrode active material comprising LiFePO ₄ or a precursor of an electrode active material and one organic compound, sprayed and dried to produce a granulated body, The particles are heat-treated at a temperature of 800 ° C. or higher and 1000 ° C. or lower in an inert atmosphere or a reducing atmosphere, and a plurality of primary particles of the electrode active material are aggregated into secondary particles, and In addition, carbon is interposed between these primary particles, and the surface of the primary particles of the electrode active material is coated with a carbonaceous film, whereby the Raman spectrum analysis of the electrode active material coated with the carbonaceous film is performed. 1360 R value is 1580 ratio peak intensities of the spectrum _{(I 1580)} at a wavelength band of ± 50 cm ^-1 in the spectrum of the peak intensity in the wavelength band of _{^{± 50cm -1 (I 1360) (}} I ₃₆₀ / _{I 1580)} of 0.65 or more and 1.00 or less, and so that only the peak derived from carbon in the wavelength band of ^{1100cm -1 ~1300cm} -1 is present, the organic compound is polyvinyl alcohol, polyvinyl pyrrolidone, Cellulose, starch, gelatin, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, polyacrylic acid, polystyrenesulfonic acid, polyacrylamide, polyvinyl acetate, glucose, fructose, galactose, mannose, maltose, sucrose, lactose, glycogen, pectin, alginate, glucomannan, chitin, hyaluronic acid, chondroitin, agarose, polyethylene glycol, polypropylene glycol, Poriguri It characterized in that it is a phosphorus or glycerol.

  The electrode of the present invention is formed using the electrode material of the present invention.

  The lithium ion battery of the present invention is characterized in that the electrode of the present invention is used as a positive electrode.

According to the electrode material of the present invention, lithium cobaltate, lithium nickelate, lithium manganate, lithium titanate, Li _x A _y D _z PO ₄ (where A is Co, Mn, Ni, Fe, Cu, Cr) One or more selected from the group, D is selected from the group of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, rare earth elements The surface of the electrode active material whose main component is one selected from the group consisting of one or more, 0 <x <2, 0 <y <1, 0 ≦ z <1.5) is a carbonaceous film. the ratio to 1360 spectral peak intensity in the wavelength band of 1580 ± 50 cm ^-1 in the spectrum of the peak intensity in the wavelength band of ± 50cm ^-1 _{(I 1360)} of the Raman spectrum analysis of the electrode material formed by coating Te _{(I 1580)} That R value since the _{(I 1360} / _{I 1580)} of 0.65 or more and 1.00 or less, and that the non-volatile components of the organic compounds in the carbonaceous film covering the surface of the electrode active material is almost no It is possible to improve the film quality of the carbonaceous film. Therefore, the electron conductivity of the carbonaceous film can be improved, Li can be removed and inserted satisfactorily, and stable charge / discharge cycle characteristics and high stability can be realized.

According to the manufacturing method of an electrode material of the present invention, lithium cobaltate, lithium nickelate, lithium manganate, lithium _{titanate, Li x A y D z PO} 4 ( where, A is Co, Mn, Ni, Fe, Cu , One or more selected from the group of Cr, D is from the group of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, rare earth elements Electrode active material or electrode active material mainly comprising one selected from the group of one or more selected, 0 <x <2, 0 <y <1, 0 ≦ z <1.5) The slurry containing the precursor and the organic compound is sprayed and dried to produce a granulated body, and the granulated body is 700 ° C. or higher and 1000 ° C. or lower in an inert atmosphere or a reducing atmosphere. Heat treatment at a temperature, and apply a carbonaceous film on the surface of the electrode active material. By forming the spectrum at 1580 wavelength band of ± 50 cm ^-1 in the spectrum of the peak intensity in the wavelength band of 1360 ± 50 cm ^-1 in the Raman spectrum analysis of the electrode active material obtained by coating at carbonaceous coat _{(I 1360)} Since the R value (I ₁₃₆₀ / I ₁₅₈₀ ), which is the ratio to the peak intensity (I ₁₅₈₀ ), is 0.65 or more and 1.00 or less, the film quality of the carbonaceous film covering the surface of the electrode active material is improved. be able to. Therefore, the electron conductivity of the carbonaceous film can be improved, Li can be removed and inserted well, and an electrode material that can realize stable charge / discharge cycle characteristics and high stability is easy. Can be manufactured.

  According to the electrode of the present invention, since it is formed using the electrode material of the present invention, the electron conductivity of the electrode can be improved.

  According to the lithium ion battery of the present invention, since the electrode of the present invention is used as a positive electrode, Li can be desorbed and inserted satisfactorily, and therefore stable charge / discharge cycle characteristics and high stability can be realized. Can do.

It is a figure which shows the waveform of the Raman spectrum containing the background of the electrode material of Example 3 and Comparative Examples 1 and 3 of the present invention. It is the figure which compared the state of the bulging of the peak of the Raman spectrum of the electrode material of Example 3 and Comparative Examples 1 and 3 of this invention. It is a figure which shows the waveform of the Raman spectrum containing the background of the electrode material of Example 6 of this invention.

The electrode material of the present invention, the production method thereof, the electrode, and the form for carrying out the lithium ion battery will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[Electrode material]
The electrode material of this embodiment, lithium cobaltate, lithium nickelate, lithium manganate, lithium _{titanate, Li x A y D z PO} 4 ( where, A is Co, Mn, Ni, Fe, Cu, the group of Cr 1 or 2 or more types selected from: D is selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements 1 The surface of the electrode active material whose main component is one selected from the group of seeds or two or more, 0 <x <2, 0 <y <1, 0 ≦ z <1.5) is a carbonaceous film a coated electrode material formed, for spectra of the peak intensity in the wavelength band of 1580 ± 50 cm ^-1 in the spectrum of the peak intensity in the wavelength band of 1360 ± 50 cm ^-1 in the Raman spectrum analysis _{(I 1360) (I 1580)} R value is _{(I 1360} / _{I 1580)} is 0.65 or more and 1.00 or less.

Selected as the electrode material, lithium cobalt acid, lithium nickel acid, lithium manganese oxide, lithium _{titanate, Li x A y D z PO} 4 ( where, A is Co, Mn, Ni, Fe, Cu, from the group of Cr One or more selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and a rare earth element It is preferable that the electrode active material is composed mainly of one or more selected from the group of 2 or more, 0 <x <2, 0 <y <1, 0 ≦ z <1.5).

Here, for A, Mn, Fe, Co, and Ni are preferable, and for D, Mg, Ca, Sr, Ti, Zn, and Al are preferable in terms of high discharge potential, abundant resources, safety, and the like.
Here, the rare earth elements are 15 elements of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu which are lanthanum series.

In this electrode material, the size of the electrode active material is not particularly limited. For example, in the case of LiMnPO ₄ , the average primary particle diameter is preferably 0.001 μm or more and 20 μm or less, more preferably It is 0.005 μm or more and 5 μm or less.
Here, the reason why the size of the primary particles of LiMnPO ₄ is in the above range is that when the average particle size of the primary particles is less than 0.001 μm, the surface of the primary particles is sufficiently covered with thin film carbon. This is because the discharge capacity in high-speed charge / discharge becomes low, and it becomes difficult to realize sufficient charge / discharge performance. On the other hand, when the average particle diameter of the primary particles exceeds 20 μm, the primary particles This is because the internal resistance increases, and the discharge capacity in high-speed charge / discharge becomes insufficient.

  In addition, the average particle diameter in this embodiment is a number average particle diameter. The average particle diameter of the primary particles can be measured using a laser diffraction / scattering particle size distribution measuring apparatus or the like.

As the electrode material, electrode active material particles coated with a carbonaceous film may be used as they are, but secondary particles formed by aggregating a plurality of electrode active material particles coated with a carbonaceous film are preferable. The shape of the secondary particles is not particularly limited, but is preferably spherical, particularly true spherical.
Here, the reason why the shape of the electrode material is preferably spherical, and particularly spherical, is that the amount of the solvent when preparing the positive electrode preparation paste by mixing the electrode material, the binder resin (binder), and the solvent. This is because it can be reduced, and the coating of the positive electrode manufacturing paste to the current collector is facilitated. If the electrode material has a spherical shape, the surface area of the electrode material is minimized, and the amount of binder resin (binder) added when preparing the positive electrode preparation paste can be minimized. This is because the internal resistance of the positive electrode obtained can be reduced.

  Furthermore, spherical, particularly true spherical electrode materials are easy to close-pack and can increase the filling amount of the electrode active material per unit volume. Therefore, the density of the electrode obtained by applying the positive electrode preparation paste can be increased, and a high-capacity lithium ion battery can be provided.

The thickness of the carbonaceous film of the electrode material, that is, the thickness of the carbonaceous film covering the surface of the electrode active material is preferably 0.1 nm or more and 20 nm or less.
The reason why the thickness of the carbonaceous film is 0.1 nm or more and 20 nm or less is that if the thickness of the carbonaceous film is less than 0.1 nm, the thickness of the carbonaceous film is too thin. It is not preferable because it cannot be sufficiently improved, and if the thickness of the carbonaceous film exceeds 20 nm, the battery activity, for example, the battery capacity per unit mass of the electrode material, is not preferable.

If subjected to Raman spectrum analysis of this electrode material, this is the peak of the spectrum in the wavelength band of ^{1000cm -1 ~1500cm} -1 of the Raman spectrum analysis is present, the half-value width Δν of the peak of the spectrum 300 cm ^-1 or less It is.
Organic Here, the half-value width Δν of the peak of the spectrum reason for the 300 cm ^-1 or less, as long as the half-value width Δν is 300 cm ^-1 or less of the peak, the carbonaceous coating covering the surface of the electrode active material This is because it is considered that the nonvolatile component of the compound is hardly present. When the half-value width Δν of the spectrum peak exceeds 300 cm ⁻¹ , the non-volatile component of the organic compound is present in the carbonaceous film, and as a result, the electronic conductivity of the carbonaceous film decreases, This is not preferable because Li removal / insertion cannot be performed satisfactorily.

In the Raman spectrum analysis of this electrode material, the R value which is the ratio of the spectral peak intensity (I ₁₃₆₀ ) in the wavelength band of 1360 ± 50 cm ^{−1 to} the spectral peak intensity (I ₁₅₈₀ ) in the wavelength band of 1580 ± 50 cm ^−1. (I ₁₃₆₀ / I ₁₅₈₀ ) is preferably 0.65 or more and 1.00 or less.

Here, the peak centered at 1580 cm ⁻¹ measured by a Raman spectroscopic spectrum indicates a state where hexagonal mesh surfaces of graphite are regularly stacked. On the other hand, the peak centered at 1360 cm ⁻¹ is considered to indicate the collapse of the hexagonal mesh surface, and this collapse of the hexagonal mesh surface proceeds at the end face of the laminated hexagonal mesh surface when viewed from Li ions. To do.
Accordingly, when the R value (I ₁₃₆₀ / I ₁₅₈₀ ) is less than 0.65, the peak intensity (I ₁₃₆₀ ) is relatively small with respect to the peak intensity (I ₁₅₈₀ ), and thus the ratio of the end faces is reduced. As a result, the insertion and desorption of Li becomes inefficient and the output decreases, which is not preferable. On the other hand, when the R value (I ₁₃₆₀ / I ₁₅₈₀ ) exceeds 1.00, the peak intensity (I ₁₃₆₀ ) Is larger than the peak intensity (I ₁₅₈₀ ), and therefore, the disorder of the stacking is too great, and as a result, the insertion / desorption reaction of Li ions is inhibited, which is not preferable.

The Raman spectrum analysis of this electrode ^material, the wavelength band of 1100cm ^-1 ~1300cm -1 preferable that there is only a peak derived from carbons.
Thereby, the non-volatile component of an organic compound does not exist in a carbonaceous film, the film quality of a carbonaceous film improves, and electronic conductivity improves.

The electrode material preferably has a powder resistance of 200 Ω · cm or less.
The powder resistance of the electrode material can be measured by a four-terminal method in which the electrode material is put into a mold, pressurized at a pressure of 50 MPa, and four probes are brought into contact with the surface of the sample.
By setting the powder resistance of the electrode material to 200 Ω · cm or less, the electronic conductivity of the electrode for a lithium ion battery to which this electrode material is applied can be improved.

[Method for producing electrode material]
The manufacturing method of the electrode material of this embodiment is lithium cobaltate, lithium nickelate, lithium manganate, lithium titanate, Li _x A _y D _z PO ₄ (where A is Co, Mn, Ni, Fe, Cu, One or more selected from the group of Cr, D is selected from the group of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, rare earth elements 1 or 2 or more, 0 <x <2, 0 <y <1, 0 ≦ z <1.5) The slurry containing the precursor and the organic compound is sprayed and dried to produce a granulated body, and the granulated body is heated to 700 ° C. or higher and 1000 ° C. or lower in an inert atmosphere or a reducing atmosphere. To form a carbonaceous film on the surface of the electrode active material. It is a method of.

Thereby, the peak of the spectrum in the wavelength band of 1580 ± 50 cm ⁻¹ of the spectrum peak intensity (I ₁₃₆₀ ) in the wavelength band of 1360 ± 50 cm ⁻¹ of the Raman spectrum analysis of the electrode active material coated with the carbonaceous film. The R value (I ₁₃₆₀ / I ₁₅₈₀ ), which is a ratio to the intensity (I ₁₅₈₀ ), can be set to 0.65 or more and 1.00 or less.

Next, the manufacturing method of the electrode material of this embodiment is demonstrated in detail.
First, an electrode active material or a precursor of an electrode active material and an organic compound are prepared.
As the electrode active material or the precursor of the electrode active material, lithium cobaltate, lithium nickelate, lithium manganate, lithium titanate, Li _x A _y D _z PO ₄ ( However, A is 1 type, or 2 or more types selected from the group of Co, Mn, Ni, Fe, Cu, Cr, D is Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, 1 or more selected from the group of Si, Ge, Sc, Y and rare earth elements, 1 selected from the group of 0 <x <2, 0 <y <1, 0 ≦ z <1.5) An electrode active material having a seed as a main component or a precursor of an electrode active material is preferred.

Here, for A, Mn, Fe, Co, and Ni are preferable, and for D, Mg, Ca, Sr, Ti, Zn, and Al are preferable in terms of high discharge potential, abundant resources, safety, and the like.
Here, the rare earth elements are 15 elements of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu which are lanthanum series.

Li _x A _y D _z compound represented by PO ₄ as _{(Li x A y D z PO} 4 powder) is a solid phase method, liquid phase method, those produced by conventional methods such as vapor phase method Can be used.
The compound (Li _x A _y D _z PO ₄ powder) is selected from the group consisting of lithium salts such as lithium acetate (LiCH ₃ COO) and lithium chloride (LiCl), or lithium hydroxide (LiOH), for example. Li source, divalent iron salts such as iron (II) chloride (FeCl ₂ ), iron (II) acetate (Fe (CH ₃ COO) ₂ ), iron (II) sulfate (FeSO ₄ ), and phosphoric acid Obtained by mixing a phosphoric acid compound such as (H ₃ PO ₄ ), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), and water. The slurry-like mixture was hydrothermally synthesized using a pressure-resistant airtight container, and the resulting precipitate was washed with water to produce a cake-like precursor material, which was obtained by firing this cake-like precursor material. compound _{(Li x} A _{y D} z P ₄ powder) can be suitably used.

  The electrode active material may be crystalline particles or amorphous particles, or may be mixed crystal particles in which crystalline particles and amorphous particles coexist. Here, the reason why the electrode active material may be amorphous particles is that the amorphous electrode active material is in an inert atmosphere of 500 ° C. or higher and 1000 ° C. or lower, preferably 800 ° C. or higher and 900 ° C. or lower. Alternatively, it is crystallized when heat-treated in a reducing atmosphere.

The size of the electrode active material is not particularly limited, but the average primary particle diameter is preferably 0.001 μm or more and 20 μm or less, more preferably 0.005 μm or more and 5 μm or less.
Here, the reason why the average particle diameter of the primary particles of the electrode active material is limited to the above range is that, if the average particle diameter of the primary particles is less than 0.001 μm, the surface of the primary particles is sufficiently thin film carbon. It is difficult to coat, and the discharge capacity at a high-speed charge / discharge rate becomes low, and it becomes difficult to realize a sufficient charge / discharge rate performance. On the other hand, the average particle diameter of primary particles is 20 μm. On the other hand, the internal resistance of the primary particles increases, and therefore, the discharge capacity at the high-speed charge / discharge rate becomes insufficient.

As the electrode material, electrode active material particles coated with a carbonaceous film may be used as they are, but secondary particles formed by aggregating a plurality of electrode active material particles coated with a carbonaceous film are preferable. The shape of the secondary particles is not particularly limited, but is preferably spherical, particularly true spherical.
Here, the reason why the shape of the electrode material is preferably spherical is that the amount of the solvent when mixing the electrode material, an organic compound such as a binder resin, and a solvent as necessary can be reduced. is there. Further, when the electrode material has a spherical shape, the surface area of the electrode material is minimized, so that the amount of the organic compound such as a binder resin added as a component of the electrode material can be minimized and the obtained positive material is obtained. This is preferable because the internal resistance of the electrode can be reduced.
In addition, since the electrode material is easy to close-pack, the filling amount of the positive electrode material per unit volume is increased, so that the electrode density can be increased, and as a result, the capacity of the lithium ion battery can be increased. This is preferable because it is possible.

Examples of the organic compound include polyvinyl alcohol, polyvinyl pyrrolidone, cellulose, starch, gelatin, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, polystyrene sulfonic acid, polyacrylamide, polyvinyl acetate, glucose, fructose, and galactose. Mannose, maltose, sucrose, lactose, glycogen, pectin, alginic acid, glucomannan, chitin, hyaluronic acid, chondroitin, agarose, polyether, polyhydric alcohol.
Examples of the polyhydric alcohol include polyethylene glycol, polypropylene glycol, polyglycerin, glycerin and the like.

Next, the electrode active material or the precursor of the electrode active material and the organic compound are dissolved or dispersed in a solvent to obtain a uniform slurry. In this dissolution or dispersion, it is more preferable to add a dispersant.
The compounding ratio of the electrode active material or the precursor of the electrode active material and the organic compound is 0.6 parts by mass with respect to 100 parts by mass of the electrode active material when the total mass of the organic compound is converted into the amount of carbon. The amount is preferably 10 parts by mass or less and more preferably 0.8 parts by mass or more and 4.0 parts by mass or less.

  Here, if the compounding ratio in terms of carbon amount of the organic compound is less than 0.6 parts by mass, the coverage on the surface of the electrode active material of the carbonaceous film produced by heat-treating this organic compound will be less than 80%, When a battery is formed, the discharge capacity at a high-speed charge / discharge rate becomes low, and it becomes difficult to realize sufficient charge / discharge rate performance. On the other hand, when the compounding ratio in terms of carbon amount of the organic compound exceeds 10 parts by mass, the compounding ratio of the electrode active material is relatively lowered, and when the battery is formed, the capacity of the battery is lowered and the carbonaceous film Due to the excessive loading, the bulk density of the electrode active material is increased. Therefore, the electrode density is decreased, and the decrease in the battery capacity of the lithium ion battery per unit volume cannot be ignored.

  As the solvent for dissolving or dispersing the electrode active material or the precursor of the electrode active material and the organic compound, water is preferable. In addition to water, for example, methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol: IPA), alcohols such as butanol, pentanol, hexanol, octanol, diacetone alcohol, esters such as ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone, Diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve) , Ethers such as diethylene glycol monomethyl ether and diethylene glycol monoethyl ether, ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetylacetone and cyclohexanone, dimethylformamide, N, N-dimethylacetoacetamide, N-methyl Examples include amides such as pyrrolidone and glycols such as ethylene glycol, diethylene glycol, and propylene glycol. These may be used alone or in combination of two or more.

  As a method for dissolving or dispersing the electrode active material or the precursor of the electrode active material and the organic compound, the electrode active material or the precursor of the electrode active material is uniformly dispersed, and the organic compound is dissolved or dispersed. For example, a method using a medium agitation type dispersing device that stirs medium particles at high speed, such as a planetary ball mill, a vibration ball mill, a bead mill, a paint shaker, and an attritor, is preferable.

  In the dissolution or dispersion, it is preferable to disperse the electrode active material or the precursor of the electrode active material as primary particles and then stir so as to dissolve the organic compound. In this way, the surface of the primary particles of the electrode active material or the precursor of the electrode active material is coated with the organic compound, and as a result, the carbon derived from the organic compound is uniformly between the primary particles of the electrode active material. Will come to intervene.

Next, using the spray pyrolysis method, the slurry is sprayed in a high-temperature atmosphere, for example, in the air of 70 ° C. or more and 250 ° C. or less, and dried to produce a granulated body.
In this spray pyrolysis method, it is preferable that the particle diameter of the droplets during spraying is 0.05 μm or more and 500 μm or less in order to quickly dry and form a substantially spherical granulated body.

Next, the granulated body is heat-treated at a temperature of 700 ° C. or higher and 1000 ° C. or lower, preferably 800 ° C. or higher and 900 ° C. or lower, in an inert atmosphere or a reducing atmosphere.
As this inert atmosphere, an atmosphere made of an inert gas such as nitrogen (N ₂ ) or argon (Ar) is preferable, and when it is desired to suppress oxidation more, a reducing property containing a reducing gas such as hydrogen (H ₂ ). An atmosphere is preferred.

Here, the reason why the heat treatment temperature is set to 700 ° C. or more and 1000 ° C. or less is that when the heat treatment temperature is less than 700 ° C., the decomposition / reaction of the organic compound does not proceed sufficiently, and the carbonization of the organic compound becomes insufficient. The decomposition / reaction product is not preferable because it becomes a high-resistance organic decomposition product. On the other hand, when the heat treatment temperature exceeds 1000 ° C., not only does the composition of the electrode active material, for example, lithium (Li) evaporate, causing a shift in the composition, but also the grain growth of the electrode active material is promoted, and high-speed charge / discharge The discharge capacity at the rate becomes low, and it becomes difficult to realize sufficient charge / discharge rate performance.
The heat treatment time is not particularly limited as long as the organic compound is sufficiently carbonized, and is, for example, 0.1 hours or more and 10 hours or less.

  When the granulated body contains a precursor of an electrode active material, the precursor of the electrode active material becomes an electrode active material, while the organic compound decomposes and reacts during the heat treatment to generate carbon. The carbon adheres to the surface of the electrode active material and forms a carbonaceous film. As a result, the surface of the electrode active material is covered with the carbonaceous film.

Here, when the electrode active material contains lithium as a constituent component, as the heat treatment time becomes longer, lithium diffuses from the electrode active material into the carbonaceous film, so that lithium is present in the carbonaceous film. This is preferable because the conductivity of the quality coating is further improved.
However, if the heat treatment time is too long, abnormal grain growth occurs or an electrode active material in which lithium is partially lost is generated, so that the performance of the electrode active material itself deteriorates. As a result, this electrode active material This is not preferable because it causes a deterioration in battery characteristics.

[electrode]
The electrode of the present embodiment is an electrode formed using the electrode material of the present embodiment.
In order to produce the electrode of this embodiment, the above-mentioned electrode material, a binder composed of a binder resin, and a solvent are mixed to prepare an electrode-forming paint or electrode-forming paste. At this time, a conductive aid such as carbon black may be added as necessary.
As the binder, that is, the binder resin, for example, polytetrafluoroethylene (PTFE) resin, polyvinylidene fluoride (PVdF) resin, fluororubber, and the like are preferably used.
The mixing ratio of the electrode material and the binder resin is not particularly limited. For example, the binder resin is 1 part by mass or more and 30 parts by mass or less, preferably 3 parts by mass or more and 20 parts by mass with respect to 100 parts by mass of the electrode material. Part or less.

  Examples of the solvent used for the electrode-forming paint or electrode-forming paste include water, methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol: IPA), butanol, pentanol, hexanol, octanol, diacetone alcohol, and the like. Alcohols, ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, esters such as γ-butyrolactone, diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol mono Ethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, diethylene Ethers such as recall monoethyl ether, ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetylacetone, cyclohexanone, amides such as dimethylformamide, N, N-dimethylacetoacetamide, N-methylpyrrolidone And glycols such as ethylene glycol, diethylene glycol, and propylene glycol. These may be used alone or in combination of two or more.

Next, this electrode-forming paint or electrode-forming paste is applied to one side of the metal foil, and then dried to form a coating film comprising a mixture of the above electrode material and binder resin on one side. Get a metal foil.
Next, this coating film is pressure-bonded and dried to produce a current collector (electrode) having an electrode material layer on one surface of the metal foil.
In this way, the electrode of this embodiment can be produced.
With this electrode, the electron conductivity of the electrode can be improved.

[Lithium ion battery]
The lithium ion battery of this embodiment is a battery having a current collector (electrode) having an electrode material layer on one surface of the metal foil of this embodiment as a positive electrode.
In the lithium ion battery of this embodiment, since it is formed by using the electrode material of this embodiment, Li desorption / insertion is improved, and thus stable charge / discharge cycle characteristics and high stability can be realized. .

According to the electrode material of the present embodiment, an electrode active material containing as a main component one selected from the group consisting of lithium cobaltate, lithium nickelate, lithium manganate, lithium titanate, and Li _x A _y D _z PO ₄ peak intensity of a spectrum in the wavelength band of 1580 ± 50 cm ^-1 in the spectrum of the peak intensity in the wavelength band of Raman spectrum analysis of ₁₃₆₀ ± 50cm ^-1 _(I 1360) of the surface electrode material formed by covering with the carbonaceous coating Since the R value (I ₁₃₆₀ / I ₁₅₈₀ ), which is a ratio to (I ₁₅₈₀ ), is set to 0.65 or more and 1.00 or less, the non-volatile organic compound is included in the carbonaceous film covering the surface of the electrode active material. As a result, almost no components are present, and as a result, the film quality of the carbonaceous film can be improved. Therefore, the electron conductivity of the carbonaceous film can be improved, Li can be removed and inserted satisfactorily, and stable charge / discharge cycle characteristics and high stability can be realized.

According to the manufacturing method of the electrode material of the present embodiment, the main component is one selected from the group consisting of lithium cobaltate, lithium nickelate, lithium manganate, lithium titanate, and Li _x A _y D _z PO _4. A slurry containing an electrode active material or a precursor of an electrode active material and an organic compound is sprayed and dried to produce a granulated body, and this granulated body is treated under an inert atmosphere or a reducing atmosphere in a 700 atmosphere. Since the carbonaceous film is formed on the surface of the electrode active material by heat-treating at a temperature of not lower than 1000 ° C and not higher than 1000 ° C, the electronic conductivity of the carbonaceous film can be improved, and the desorption / insertion of Li is good It is possible to easily produce an electrode material that can achieve stable charge / discharge cycle characteristics and high stability.

According to the electrode of this embodiment, since it was formed using the electrode material of this embodiment, the electron conductivity of the electrode can be improved.
According to the electrode of the present invention, since it is formed using the electrode material of the present invention, the electron conductivity of the electrode can be improved.

  According to the lithium ion battery of this embodiment, since the current collector (electrode) of this embodiment is a positive electrode, Li can be desorbed and inserted satisfactorily, and thus stable charge / discharge cycle characteristics and High stability can be achieved.

Hereinafter, a detailed explanation of the present invention through examples 3-6 and Comparative Example 1-4, the present invention is not intended to be limited to these examples.
For example, in this embodiment, metal Li is used for the negative electrode in order to reflect the behavior of the electrode material itself in the data. However, a negative electrode material such as a carbon material, a Li alloy, or Li ₄ Ti ₅ O ₁₂ may be used. . A solid electrolyte may be used instead of the electrolytic solution and the separator.

A. Production and Evaluation of Electrode Material “ Comparative Example 3 ”
(Production of electrode material)
To 2 L (liter) of water, 4 mol of lithium acetate (LiCH ₃ COO), 2 mol of iron (II) sulfate (FeSO ₄ ), 2 mol of phosphoric acid (H ₃ PO ₄ ) were added and mixed, and the total amount was 4 L ( L) to prepare a uniform slurry mixture.
Next, this mixture was placed in a pressure-resistant sealed container having a capacity of 8 L (liter), hydrothermally synthesized at 120 ° C. for 1 hour, and the resulting precipitate was washed with water to obtain a cake-like electrode active material precursor. .
Next, a polyethylene glycol aqueous solution in which 5.5 g of polyethylene glycol as an organic compound is dissolved in 150 g of water is added to 150 g of the precursor of the electrode active material (in terms of solid content), and the mixture is put into a ball mill. Zirconia balls (500 g) were added, and dispersion treatment was performed for 12 hours using this ball mill to prepare a uniform slurry.

Next, this slurry was sprayed into an air atmosphere at 180 ° C. and dried to obtain a granulated body having an average particle diameter of 6 μm.
The obtained granulated body was fired at 700 ° C. for 1 hour under an inert atmosphere made of nitrogen (N ₂ ) gas to obtain an electrode material (A1).

(Evaluation of electrode material)
When this electrode material (A1) was observed with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), a plurality of primary particles gathered to form secondary particles, and the surface of these primary particles. Was covered with a thin film of carbon, and it was observed that carbon was present between the primary particles. The electrode material (A1) was spherical with an average particle diameter of 5 μm.

Further, the wavelength 513nm of the electrode material (A1) was subjected to Raman spectrum analysis using an argon ion laser beam, in the wavelength band of 1000～1500Cm ^-1 it has a peak of the spectrum in 1360 cm ^-1, the spectrum The full width at half maximum Δν ₁₃₆₀ was 263 cm ⁻¹ .
Further, an R value (I ₁₃₆₀ / I ₁₅₈₀ ) which is a ratio of the spectrum peak intensity (I ₁₃₆₀ ) in the wavelength band of 1360 ± 50 cm ^{−1 to} the spectrum peak intensity (I ₁₅₈₀ ) in the wavelength band of 1580 ± 50 cm ^−1. Was 0.83.
Furthermore, it was present different broad small peak and carbon derived from the wavelength band of 1100～1300Cm ^-1 and 1400~1500cm ^-1.

  Moreover, this electrode material (A1) was put into a metal mold and molded at a pressure of 50 MPa to prepare a measurement sample. And the powder resistance of this electrode material (A1) was measured by the 4 terminal method at 25 degreeC using the low resistivity meter Loresta-GP (made by Mitsubishi Chemical Corporation). As a result, the powder resistance of this electrode material (A1) was 155 Ω · cm.

" Comparative Example 4 "
The electrode material (A2) of Comparative Example 4 was obtained according to Comparative Example 3 , except that the granulated body was fired at 750 ° C. for 1 hour.
This electrode material (A2) was evaluated according to Comparative Example 3 .
As a result, in observation with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), as in the electrode material (A1), a plurality of primary particles are aggregated into secondary particles, and these primary particles The surface of was covered with a thin film of carbon, and it was observed that carbon was present between the primary particles. The electrode material (A2) was spherical with an average particle diameter of 5 μm.

The place where the electrode material Raman spectrum analysis of the (A2) was carried out in accordance with Comparative Example 3, there is a peak of the spectrum 1360 cm ^-1, the half width .DELTA..nu ₁₃₆₀ of the spectrum was 240 cm ^-1.
The R value (I ₁₃₆₀ / I ₁₅₈₀ ) was 0.88.
Furthermore, it was present different broad small peaks and carbon derived from the wavelength band of 1100～1300Cm ^-1 and 1400~1500cm ^-1.
Moreover, when the powder resistance of this electrode material (A2) was measured according to Comparative Example 3 , the powder resistance of this electrode material (A2) was 102 Ω · cm.

"Example 3"
An electrode material (A3) of Example 3 was obtained in accordance with Comparative Example 3 except that the granulated body was fired at 800 ° C. for 1 hour.
This electrode material (A3) was evaluated according to Comparative Example 3 .
As a result, in observation with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), as in the electrode material (A1), a plurality of primary particles are aggregated into secondary particles, and these primary particles The surface of was covered with a thin film of carbon, and it was observed that carbon was present between the primary particles. The electrode material (A3) was spherical with an average particle diameter of 5 μm.

The place where the electrode material a Raman spectrum analysis (A3) was carried out in accordance with Comparative Example 3, there is a peak of the spectrum 1360 cm ^-1, the half width .DELTA..nu ₁₃₆₀ of the spectrum was 220 cm ^-1.
The R value (I ₁₃₆₀ / I ₁₅₈₀ ) was 0.96.
Furthermore, it did not exist different peaks with carbon derived from the wavelength band of 1100～1300Cm ^-1 and 1400~1500cm ^-1.
Moreover, when the powder resistance of this electrode material (A3) was measured according to Comparative Example 3 , the powder resistance of this electrode material (A3) was 10 Ω · cm.

Example 4
An electrode material (A4) of Example 4 was obtained in accordance with Comparative Example 3 except that the granulated body was fired at 850 ° C. for 1 hour.
This electrode material (A4) was evaluated according to Comparative Example 3 .
As a result, in observation with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), as in the electrode material (A1), a plurality of primary particles are aggregated into secondary particles, and these primary particles The surface of was covered with a thin film of carbon, and it was observed that carbon was present between the primary particles. The electrode material (A4) was spherical with an average particle diameter of 5 μm.

The place where the electrode material Raman spectrum analysis of the (A4) was carried out in accordance with Comparative Example 3, there is a peak of the spectrum 1360 cm ^-1, the half width .DELTA..nu ₁₃₆₀ of the spectrum was 181cm ^-1.
The R value (I ₁₃₆₀ / I ₁₅₈₀ ) was 0.98.
Furthermore, it did not exist different peaks with carbon derived from the wavelength band of 1100～1300Cm ^-1 and 1400~1500cm ^-1.
Moreover, when the powder resistance of this electrode material (A4) was measured according to Comparative Example 3 , the powder resistance of this electrode material (A4) was 12 Ω · cm.

"Example 5"
An electrode material (A5) of Example 5 was obtained in accordance with Comparative Example 3 except that the granulated body was fired at 900 ° C. for 1 hour.
This electrode material (A5) was evaluated according to Comparative Example 3 .
As a result, in observation with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), as in the electrode material (A1), a plurality of primary particles are aggregated into secondary particles, and these primary particles The surface of was covered with a thin film of carbon, and it was observed that carbon was present between the primary particles. The electrode material (A5) was spherical with an average particle diameter of 5 μm.

The place where the electrode material a Raman spectrum analysis (A5) was carried out in accordance with Comparative Example 3, there is a peak of the spectrum 1360 cm ^-1, the half width .DELTA..nu ₁₃₆₀ of the spectrum was 172cm ^-1.
The R value (I ₁₃₆₀ / I ₁₅₈₀ ) was 0.99.
Furthermore, it did not exist different peaks with carbon derived from the wavelength band of 1100～1300Cm ^-1 and 1400~1500cm ^-1.
Moreover, when the powder resistance of this electrode material (A5) was measured according to Comparative Example 3 , the powder resistance of this electrode material (A5) was 8 Ω · cm.

"Example 6"
A slurry was prepared in accordance with Comparative Example 3 using manganese sulfate (II) (MnSO ₄ ) as a manganese source instead of iron sulfate (II) (FeSO ₄ ) serving as an iron source. Next, this slurry was sprayed into an air atmosphere at 180 ° C. and dried to obtain a granulated body having an average particle size of 5 μm.
The obtained granulated body was fired at 800 ° C. for 1 hour under an inert atmosphere made of nitrogen (N ₂ ) gas to obtain an electrode material (A6).

This electrode material (A6) was evaluated according to Comparative Example 3 .
As a result, in observation with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), as in the electrode material (A1), a plurality of primary particles are aggregated into secondary particles, and these primary particles The surface of was covered with a thin film of carbon, and it was observed that carbon was present between the primary particles. The electrode material (A6) was spherical with an average particle diameter of 5 μm.

The place where the electrode material a Raman spectrum analysis (A6) was carried out in accordance with Comparative Example 3, there is a peak of the spectrum 1360 cm ^-1, the half width .DELTA..nu ₁₃₆₀ of the spectrum was 260 cm ^-1.
The R value (I ₁₃₆₀ / I ₁₅₈₀ ) was 0.91.
Furthermore, it did not exist different peaks with carbon derived from the wavelength band of 1100～1300Cm ^-1 and 1400~1500cm ^-1.
Moreover, when the powder resistance of this electrode material (A6) was measured according to Comparative Example 3 , the powder resistance of this electrode material (A6) was 11 Ω · cm.

“Comparative Example 1”
An electrode material (B1) of Comparative Example 1 was obtained in accordance with Comparative Example 3 , except that the granulated body was fired at 500 ° C. for 1 hour.
This electrode material (B1) was evaluated according to Comparative Example 3 .
As a result, in observation with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), as in the electrode material (A1), a plurality of primary particles are aggregated into secondary particles, and these primary particles The surface of was covered with a thin film of carbon, and it was observed that carbon was present between the primary particles. The electrode material (B1) was spherical with an average particle diameter of 5 μm.

When the Raman spectrum analysis of this electrode material (B1) was conducted according to Comparative Example 3 , there was a spectrum peak at 1360 cm ⁻¹ and the half-value width Δν ₁₃₆₀ of this spectrum was 361 cm ⁻¹ .
The R value (I ₁₃₆₀ / I ₁₅₈₀ ) was 0.58.
Furthermore, it was present different peaks with carbon derived from the wavelength band of 1100～1300Cm ^-1 and 1400~1500cm ^-1.
Moreover, when the powder resistance of this electrode material (B1) was measured according to Comparative Example 3 , the powder resistance of this electrode material (B1) was 1000 Ω · cm.

“Comparative Example 2”
An electrode material (B2) of Comparative Example 2 was obtained in accordance with Comparative Example 3 except that the granulated body was fired at 600 ° C. for 1 hour.
This electrode material (B2) was evaluated according to Comparative Example 3 .
As a result, in observation with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), as in the electrode material (A1), a plurality of primary particles are aggregated into secondary particles, and these primary particles The surface of was covered with a thin film of carbon, and it was observed that carbon was present between the primary particles. The electrode material (B2) was spherical with an average particle diameter of 5 μm.

The place where the electrode material Raman spectrum analysis of the (B2) was carried out in accordance with Comparative Example 3, there is a peak of the spectrum 1360 cm ^-1, the half width .DELTA..nu ₁₃₆₀ of the spectrum was 298cm ^-1.
The R value (I ₁₃₆₀ / I ₁₅₈₀ ) was 0.61.
Furthermore, it was present different peaks with carbon derived from the wavelength band of 1100～1300Cm ^-1 and 1400~1500cm ^-1.
Moreover, when the powder resistance of this electrode material (B2) was measured according to Comparative Example 3 , the powder resistance of this electrode material (B2) was 281 Ω · cm.

Table 1 shows the results of Raman spectra of Examples 3 to 6 and Comparative Examples 1 to 4 .
In addition, FIGS. 1 and 2 show Raman spectrum waveforms of Example 3 and Comparative Examples 1 and 3, respectively.
Incidentally, FIG. 1 shows the Raman spectrum of the waveform including a back ground Wound, 2, move the spectral intensity of 1350cm ^-1, 1100~1300cm ^-1 at spectral peaks in a wavelength band of 1000～1500Cm ^-1 And the result of having compared the state of the swelling of the peak of 1400-1500cm < ^-1 > is shown.
Moreover, the waveform of the Raman spectrum including the background of Example 6 is shown in FIG.

According to the above results, it can be seen that the electrode materials of Examples 3 to 5 have a smaller half-value width Δν ₁₃₆₀ than the electrode materials of Comparative Examples 1 and 2, and the half-value width is further reduced by raising the firing temperature. .
The electrode material of Comparative Examples 3 and 4, in the spectrum of the peak in the wavelength band of 1000～1500Cm ^-1, but different spectra appear from the carbon derived from 1100～1300Cm ^-1 and 1400～1500Cm ^-1, this The spectrum disappears as the firing temperature is increased, and the electrode materials of Examples 3 to 6 were fired at 800 ° C. or higher, so that the peak of the spectrum in the wavelength band of 1000 to 1500 cm ⁻¹ was 1100 to 1300 cm. ^No spectrum different from that derived from carbon appeared at ^-1 and 1400-1500 cm- ¹ .

B. Fabrication and evaluation of lithium ion battery (production of lithium ion battery)
Using examples 3-6 and Comparative Examples 1-4 Each of the electrode materials were produced in Example 3-6 and Comparative Example 1-4 each lithium ion battery.
First, 90 parts by mass of an electrode material, 5 parts by mass of acetylene black as a conductive auxiliary agent, 5 parts by mass of polyvinylidene fluoride (PVDF) as a binder, and N-methyl-2-pyrrolidinone (NMP) as a solvent were mixed.
Next, these were kneaded using a three-roll mill to prepare an electrode forming paste.

Next, this electrode forming paste was applied onto an aluminum current collector foil having a thickness of 30 μm, and then dried under reduced pressure at 120 ° C. to produce a positive electrode having a thickness of 60 μm.
Next, this positive electrode was punched into a 2 cm ² disk shape, dried under reduced pressure, and then a lithium ion battery was produced using a stainless steel 2016 coin cell in a dry argon atmosphere.
Here, metallic lithium is used for the negative electrode, a porous polypropylene film is used for the separator, and 1 mol of LiPF ₆ is mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a ratio of 1: 1. A mixture mixed into the mixed solution was used.

(Evaluation of lithium-ion battery)
Evaluation of each of the lithium ion batteries of Examples 3 to 6 and Comparative Examples 1 to 4 was performed based on the battery charge / discharge characteristics and the cycle characteristic maintenance rate. The test method is as follows.
(1) Battery charge / discharge characteristics The cut-off voltage was set to 2.0 V to 4.0 V, the battery was charged at 0.1 C, discharged at 0.1 C, and the initial discharge capacity was measured.

(2) Cycle characteristic maintenance ratio Cutoff voltage is 2.0V to 4.0V, measurement temperature is 60 ° C, 1C discharge is 1 cycle after 1C charge, and the percentage of capacity at 600th cycle to the capacity of the first cycle is The cycle characteristic retention rate was used.
Table 2 shows the battery charge / discharge characteristics and the cycle characteristic maintenance ratios of Examples 3 to 6 and Comparative Examples 1 to 4 .

According to the above results, the lithium ion batteries of Examples 3 to 6 have a higher initial discharge capacity in battery charge / discharge characteristics than the lithium ion batteries of Comparative Examples 1 and 2, and have stable charge / discharge performance. And high output performance was achieved.
In particular, the lithium ion batteries of Examples 3 to 5 were superior to the lithium ion battery of Example 6 in the cycle characteristic maintenance ratio and showed a high discharge capacity. The reason is considered to be that the film quality of the carbonaceous film has been improved, so that the electron conductivity works well and the battery characteristics are improved.

Claims (6)

A plurality of primary particles of the electrode active material made of LiFePO ₄ are aggregated to form secondary particles, and carbon is interposed between the primary particles, and the surface of the primary particles of the electrode active material is coated with a carbonaceous film. An electrode material coated with
The R value (I ₁₃₆₀ / I) is the ratio of the spectral peak intensity (I ₁₃₆₀ ) in the wavelength band of 1360 ± 50 cm ^{−1 to} the spectral peak intensity (I ₁₅₈₀ ) in the wavelength band of 1580 ± 50 cm ⁻¹ in Raman spectral analysis. ₁₅₈₀₎ is 0.65 or more and 1.00 or less, and electrode material in the wavelength band of ^{1100cm -1 ~1300cm} -1 is characterized by the presence of only a peak derived from carbons. The Raman spectral analysis peaks in the spectrum are present in a wavelength band of ^{1000cm -1 ~1500cm} -1 of the electrode material according to claim 1, wherein the half-value width Δν of a peak of the spectrum is 300 cm ^-1 or less .   The electrode material according to claim 1, wherein the powder resistance is 200 Ω · cm or less. A slurry containing an electrode active material composed of LiFePO ₄ or a precursor of the electrode active material and one organic compound is sprayed and dried to form a granulated body, and the granulated body is subjected to an inert atmosphere or reduced. Heat treatment at a temperature of 800 ° C. or higher and 1000 ° C. or lower in a neutral atmosphere, a plurality of primary particles of the electrode active material are aggregated to become secondary particles, and carbon is interposed between the primary particles. Further, by covering the surface of the primary particles of the electrode active material with a carbonaceous film, the spectrum in the wavelength band of 1360 ± 50 cm ⁻¹ of the Raman spectrum analysis of the electrode active material coated with the carbonaceous film R value 1580 is the ratio to the peak intensity of the spectrum _{(I 1580)} at a wavelength band of ± 50 cm ^-1 of the peak intensity _{(I 1360) (I 1360 /} I 1580) 0.6 Or more and 1.00 or less, and so there is only a peak derived from carbons in the wavelength band of ^{1100cm -1 ~1300cm} -1,
The organic compound is polyvinyl alcohol, polyvinyl pyrrolidone, cellulose, starch, gelatin, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, polystyrene sulfonic acid, polyacrylamide, polyvinyl acetate, glucose, fructose, galactose, mannose. , Maltose, sucrose, lactose, glycogen, pectin, alginic acid, glucomannan, chitin, hyaluronic acid, chondroitin, agarose, polyethylene glycol, polypropylene glycol, polyglycerin, or glycerin . An electrode comprising the electrode material according to any one of claims 1 to 3 as a forming material .   A lithium ion battery comprising the electrode according to claim 5 as a positive electrode.

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