JP2014179292A - Electrode material, method for manufacturing the same, and electrode, and lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode material which enables the further improvement of the high rate characteristic, especially further decrease in DC resistance (DCR), a method for manufacturing such an electrode material, an electrode, and a lithium ion battery.SOLUTION: An electrode material of the invention comprises an aggregate including carbonaceous material-coated electrode active material particles. The carbonaceous material-coated electrode active material particles each include a LiADPO(where A is at least one element selected from a group consisting of Co, Mn, Ni, Fe, Cu, and Cr, and D is at least one element selected from a group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, and x, y, and z satisfy the following conditions: 0<x≤2, 0<y≤1, and 0≤z≤1.5) particle and a carbonaceous coating film coating the surface thereof. The aggregate has a BET value of 8-40 m/g, an average pore size of 0.5 μm or smaller, and a pore distribution which describes a single-peak curve. The aggregate includes therein 0.3-3.0 mass% of conductive assistant to the LiADPOparticles.

Description

  TECHNICAL FIELD The present invention relates to an electrode material, a manufacturing method thereof, an electrode, and a lithium ion battery, and more particularly to an electrode material suitable for use in a positive electrode material for a battery, and further to a positive electrode material for a lithium ion battery, and a manufacturing method thereof. The present invention relates to a lithium ion battery including an electrode containing a material and a positive electrode made of the electrode.

  In recent years, with the rapid development of clean energy technology, it is necessary to create an environment that is friendly to the earth, such as oil removal, zero emissions, and the spread of power-saving products. In particular, high-capacity storage batteries that supply electric energy to electric vehicles are attracting attention recently, large-capacity storage batteries that supply electric energy in the event of an emergency or disaster, portable information devices, and portable information A secondary battery that supplies electrical energy to a terminal or the like, for example, a lead storage battery, an alkaline storage battery, or a lithium ion battery is known. In particular, lithium ion batteries can be reduced in size, weight and capacity, and have excellent characteristics of high output and high energy density. Are also commercialized as high-output power supplies such as, and the development of materials for next-generation lithium-ion batteries is becoming active all over the world.

  Recently, HEMS (Home Energy Management System), which has been in the limelight as a collaboration between large-capacity storage batteries that supply electrical energy and houses, It is a system that intelligently consumes energy by managing information related to electricity and control systems to manage automatic control and optimization of power supply and demand.

LiCoO ₂ and LiMnO ₂ are generally used as the electrode active material used for the positive electrode of the lithium ion battery currently in practical use. However, since Co is unevenly distributed on the earth, and a rare resource, when used in large quantities, the product cost becomes high, and there is a problem that a stable supply is difficult, therefore, to LiCoO ₂ Alternative positive electrode active materials include spinel LiMn ₂ O ₄ , ternary LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , lithium ferrate (LiFeO ₂ ), lithium iron phosphate (LiFePO ₄ ), etc. Research and development of positive electrode active materials is actively underway.
Among these positive electrode materials, LiFePO ₄ having an olivine structure has attracted attention as a positive electrode material having no problem in terms of resources and costs as well as safety.
Since the olivine-based positive electrode material represented by this LiFePO ₄ contains phosphorus as a constituent element and is strongly covalently bonded to oxygen, there is no risk of releasing oxygen at a higher temperature than a positive electrode material such as LiCoO ₂ . There is no risk of ignition due to oxidative decomposition of the electrolyte, and the material is excellent in safety.

However, even in LiFePO ₄ having such advantages, there is a problem that the electronic conductivity is low, and this low electronic conductivity is caused by the slow diffusion of lithium ions inside the active material derived from the structure and the electronic conductivity. It is thought that it is in low.
Therefore, as an electrode material with improved electron conductivity, for example, Li _x A _y B _z PO ₄ (where A is one or two selected from the group of Co, Mn, Ni, Fe, Cu, Cr) As described above, B is one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, and 0 < A plurality of primary particles of an electrode active material composed of x <2, 0 <y <1, 0 ≦ z <1.5) are aggregated to form secondary particles, and between these primary particles, electron conductivity There has been proposed an electrode material in which carbon is interposed as a substance and the surface of the electrode active material is covered with a carbonaceous film. Moreover, as a manufacturing method of these electrode materials, a slurry containing an electrode active material or an electrode active material precursor and an organic compound is sprayed and dried to generate a granulated body, and this granulated body is generated. And the method of heat-processing this granulated body in 500 degreeC or more and 1000 degreeC or less non-oxidizing atmosphere is proposed (for example, refer patent documents 1-3).

Further, a positive electrode material for a lithium ion secondary battery in which the content of carbon in a composite of LiFePO ₄ and carbon is 1 to 20% by mass (Patent Document 4), a lithium-containing phosphate having an average particle size of 1 μm or less And a positive electrode active material for a lithium ion secondary battery (patent document 5) composed of a lithium-containing phosphate aggregate having an average particle size of 3 μm or less. Yes.
These positive electrode active materials are said to be capable of coating the carbonaceous material with a uniform thickness by improving the granule density, thereby improving battery characteristics. In addition, the density of the positive electrode active material in the electrode can be increased by increasing the density, the capacity can be increased, and further, the diffusion distance of lithium ions can be shortened by increasing the density. It is said that ion diffusibility can be improved and ion conductivity in the positive electrode can be improved.

Furthermore, a method for producing a positive electrode active material for a lithium ion secondary battery was obtained by dispersing or dissolving particles made of a positive electrode active material, particles made of a conductive auxiliary agent, and a binder in a solvent. A method has been proposed in which conductive auxiliary agent particles are arranged on the surface of positive electrode active material particles by spraying a dispersion and drying (Patent Document 6).
In this manufacturing method, it is said that a positive electrode active material having reduced high rate characteristics, particularly direct current resistance (DCR), can be obtained by disposing conductive auxiliary agent particles on the surface of the positive electrode active material particles.
In addition, in order to make the particles made of the positive electrode active material contain an excessive conductive auxiliary agent, a direct current resistance (DCR) can be obtained by adding a conductive auxiliary agent such as CB or KB when firing the raw material by the solid phase method. A reduced positive electrode active material has been proposed (Patent Document 7).

JP 2004-014340 A JP 2004-014341 A JP 2001-015111 A JP 2006-032241 A JP 2009-048958 A JP 2009-259698 A JP 2008-183436 A

By the way, in recent years, further improvement in high-rate characteristics has been demanded in electrode materials for lithium ion batteries, and in particular, reduction in direct current resistance (DCR) has been demanded.
However, in the electrode materials of Patent Documents 1 to 5, since a large amount of carbonaceous film remains on the surface of the electrode active material, the thickness of the carbonaceous film increases, and this thick carbonaceous film is subjected to lithium diffusion. There is a problem that the high-rate characteristic is lowered, particularly the direct current resistance (DCR) is increased.

In the electrode material of Patent Document 6, since the surface of the positive electrode active material is coated with carbon particles as a conductive auxiliary agent, it becomes a discontinuous carbonaceous coating, resulting in poor electronic conductivity and high rate characteristics. There was a problem that it was greatly reduced.
In the electrode material of Patent Document 7, the addition of an excessive conductive auxiliary agent improves the electronic conductivity in the positive electrode active material and contributes to the reduction of direct current resistance (DCR), but the conductive auxiliary agent itself has a low bulk density. As a result, the electrode density is lowered, and as a result, the adhesiveness to the electrode is lowered. Therefore, it is necessary to increase the binder in addition to the addition amount, which causes a decrease in the energy density of the battery. It was.

  The present invention has been made to solve the above-described problems, and further provides an electrode material capable of further improving high-rate characteristics, in particular, further reducing direct current resistance (DCR), a manufacturing method thereof, and an electrode material thereof. Provided with a lithium ion battery having sufficient durability and high discharge capacity at a high-speed charge / discharge rate and having sufficient charge / discharge rate performance by having an electrode containing and a positive electrode made of this electrode Objective.

As a result of intensive studies to solve the above problems, the present inventors have determined that Li _x A _y D _z PO ₄ (where A is selected from the group of Co, Mn, Ni, Fe, Cu, and Cr). 1 type or 2 types or more, D is 1 type or 2 types selected from the group of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements As described above, 0 <x ≦ 2, 0 <y ≦ 1, 0 ≦ z ≦ 1.5) The BET value of the aggregate composed of carbonaceous coated electrode active material particles obtained by coating the surface of the particles with a carbonaceous coating is 8 m. ² / g or more and 40 m ² / g or less, the average pores are 0.5 μm or less, the pore distribution is unimodal, and a conductive auxiliary agent is incorporated into the Li _x A _y D _z PO ₄ particles inside the aggregate. On the other hand, if 0.3% by mass or more and 3.0% by mass or less are contained, the lithium ion conductivity is impaired. Without improves the electronic conductivity, thus, improved high rate characteristics, in particular found that the DC resistance (DCR) is greatly reduced, thereby completing the present invention.

That is, the electrode material of the present invention is Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr, D is Mg, One or more selected from the group of Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, 0 <x ≦ 2, 0 <y ≦ 1, 0 ≦ z ≦ 1.5) an aggregate composed of carbonaceous coated electrode active material particles obtained by coating the surface of the particles with a carbonaceous film,
The BET value of the aggregate is 8 m ² / g or more and 40 m ² / g or less, the average pore is 0.5 μm or less, and the pore distribution is unimodal. _x A _y D _z PO ₄ particles are contained in an amount of 0.3 mass% or more and 3.0 mass% or less.

The volume density of the aggregate is preferably 35% by volume or more and 50% by volume or less of the volume density when the aggregate is solid.
The conductive auxiliary agent is carbon particles, and is contained in an aggregate composed of the carbonaceous coated electrode active material particles as a conductive auxiliary agent particle aggregate in which fine particles having an average primary particle diameter of 50 nm or less are aggregated. It is preferable.
The iron content in the conductive assistant is 0.1% by mass to 10.0% by mass, the phosphorus content is 0.1% by mass to 10.0% by mass, and the oxygen content is 0%. It is preferable that they are 1 mass% or more and 10.0 mass% or less.

A method for producing an electrode material according to the present invention is a method for producing the above electrode material, wherein the Li _x A _y D _z PO ₄ particles or a precursor thereof, an organic compound, and a conductive additive are dissolved or dissolved in a solvent. A conductive additive formed by coating the surface of the Li _x A _y D _z PO ₄ particles with a carbonaceous film by performing a mechanochemical treatment after dispersion, or after being dissolved or dispersed, and then spraying and drying. An aggregate comprising carbonaceous coated electrode active material particles is obtained.

The electrode of the present invention is characterized by containing the electrode material of the present invention.
The lithium ion battery of the present invention includes a positive electrode comprising the electrode of the present invention.

According to the electrode material of the present invention, Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr, D is Mg, One or more selected from the group of Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, 0 <x ≦ 2, 0 <y ≦ 1, 0 ≦ z ≦ 1.5) The BET value of the aggregate composed of carbonaceous coated electrode active material particles formed by coating the surface of the particles with a carbonaceous coating is 8 m ² / g or more and 40 m ² / g or less, The average pore size is 0.5 μm or less, the pore distribution is unimodal, and the conductive assistant is contained in the aggregate in an amount of 0.3% by mass or more with respect to the Li _x A _y D _z PO ₄ particles. Since 0% by mass or less is contained, the electron conductivity and the ion conductivity are not impaired without impairing the lithium ion conductivity. It is possible to improve the resistance. Therefore, high-rate characteristics can be improved, and particularly direct current resistance (DCR) can be greatly reduced.

According to the method for producing an electrode material of the present invention, Li _x A _y D _z PO ₄ particles or a precursor thereof, an organic compound, and a conductive additive are dissolved or dispersed in a solvent, or after being dissolved or dispersed. subjected to chemical treatment and then, by spray-drying, agglomerate consisting of Li _x a _y D _z PO ₄ carbon coated electrode active material particles to the surface of the particles comprising an electrically conducting additive comprising coated by carbonaceous coating film Therefore, it is possible to easily and inexpensively manufacture an electrode material that can improve high-rate characteristics, and in particular, can greatly reduce direct current resistance (DCR).

  According to the electrode of the present invention, since the electrode material of the present invention is contained, high-rate characteristics can be improved, and in particular, direct current resistance (DCR) can be greatly reduced.

  According to the lithium ion battery of the present invention, since the positive electrode comprising the electrode of the present invention is provided, the high-rate characteristics are improved, and in particular, the direct current resistance (DCR) is greatly reduced, so that the durability is good and the high speed charge is achieved. The discharge capacity at the discharge rate is high, and sufficient charge / discharge rate performance can be achieved.

It is a scanning transmission electron microscope (STEM) image which shows the electrode of Example 2 of this invention. It is a figure which shows the surface analysis result by EDX in "001" of the electrode of Example 2 of this invention. It is a figure which shows the surface analysis result by EDX in "002" of the electrode of Example 2 of this invention.

The electrode material of the present invention, its manufacturing method, 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 the present embodiment is Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, and Cr, and 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, 0 <x ≦ 2, 0 <y ≦ 1, 0 ≦ z ≦ 1.5) an aggregate composed of carbonaceous coated electrode active material particles obtained by coating the surface of the particle with a carbonaceous film, wherein the aggregate has a BET value of 8 m ² / g or more and 40 m ² / g or less, average pore size is 0.5 μm or less, and the pore distribution is unimodal, and a conductive assistant is added to the inside of the agglomerate with respect to the Li _x A _y D _z PO ₄ particles. This is an electrode material containing 3% by mass or more and 3.0% by mass or less.

The Li _x A _y D _z PO ₄ particles as the electrode active material particles are Co, Mn, Ni, Fe for A, Mg, Ca, Sr, Ba, Ti, Zn, Al for D, It is preferable because a high discharge potential is easily obtained.
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.

  Here, the aggregate composed of carbonaceous coated electrode active material particles means that the carbonaceous coated electrode active material particles are aggregated in a state where they are in contact with each other to form one structure. Although it does not specifically limit as a state which contacted, It is preferable that it is an aggregate of the state where the contact area of particle | grains is small and the contact part became a neck shape with a small cross-sectional area, and was connected firmly. Thus, the contact portion between the electrode active material particles of the carbon-coated electrode active material particles becomes a neck shape with a small cross-sectional area, so that a channel-like (mesh-like) void is three-dimensionally inside the aggregate. Expanded structure.

In addition, in this carbon-coated electrode active material particle, when used as an electrode material of a lithium ion battery, in order to uniformly perform a reaction related to lithium ion desorption / insertion on the entire surface of the electrode active material particle, It is preferable that 80% or more, preferably 90% or more of the surface is covered with a carbonaceous film.
The coverage of a carbonaceous film can be measured using a transmission electron microscope (TEM) and an energy dispersive X-ray spectrometer (EDX). Here, when the coverage of the carbonaceous film is less than 80%, the coating effect of the carbonaceous film is insufficient, and the carbonaceous film is formed when the lithium ion deinsertion reaction is performed on the surface of the electrode active material. This is not preferable because the reaction resistance related to lithium ion desorption / insertion is increased at a portion where the discharge is not performed, and the voltage drop at the end of discharge becomes remarkable.

The thickness of the carbonaceous film in the carbonaceous coated electrode active material particles of the aggregate is preferably 0.1 nm or more and 20 nm or less.
Here, if the thickness of the carbonaceous film is less than 0.1 nm, the thickness of the carbonaceous film is too thin, and the electronic conductivity of the carbonaceous coated electrode active material particles themselves is lowered, which is not preferable. On the other hand, 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 may decrease, which is not preferable.

The volume density of the aggregate is preferably 35 volume% or more and 50 volume% or less, more preferably 40 volume% or more and 50 volume% or less of the volume density when the aggregate is solid.
Here, the solid aggregate is an aggregate having no voids at all, and the density of the solid aggregate is equal to the theoretical density of the electrode active material.

  This volume density can be measured using a mercury porosimeter, and is calculated from the mass of the entire electrode material constituted by the aggregate and the volume of the gap between the particles constituting the aggregate. is there. In other words, it is calculated from the particle gap inside the aggregate particle obtained by removing the gap between the particles from the total volume of the particle gap constituting the aggregate, and the mass of the entire electrode material constituted by the aggregate. It is the density of the aggregate to be formed.

  Thus, by setting the volume density of the aggregate to 35 volume% or more and 50 volume% or less, the aggregate is densified in a state having pores (voids) of 50 volume% or more of the volume. The carbonaceous material can be permeated into the pores (voids) in the aggregate. Therefore, the electronic conductivity can be improved without impairing the lithium ion conductivity, and as a result, the high-rate characteristics can be improved, and in particular, the direct current resistance (DCR) can be greatly reduced.

The specific surface area (BET value) of the aggregate can be measured by a BET method using nitrogen (N ₂ ) adsorption or the like.
The specific surface area (BET value) of the aggregate is preferably 8 m ² / g or more and 40 m ² / g or less, more preferably 10 m ² / g or more and 35 m ² / g or less, more preferably 11 m ² / g or more and 30 m ² / g or less.
Here, if the BET value of the aggregate is less than 8 m ² / g, it is not preferable because the Li diffusion movement distance moving in the particles becomes long, and thus the resistance component becomes large. On the other hand, the BET value of the aggregate is 15 m. If it exceeds ² / g, the crystallinity of the particles is lowered, which causes a decrease in energy density, which is not preferable.

The average pores of the aggregate are preferably 0.5 μm or less, more preferably 0.4 μm or less, and still more preferably 0.3 μm or less.
Here, when the average pores of the aggregates exceed 0.5 μm, the volume density of the aggregates is less than 35% by volume, and the binder penetrates into the aggregates when the electrode slurry is prepared. As a result, the amount of the binder that connects the agglomerated particles decreases, and the strength of the electrode film formed as a coating film decreases, which is not preferable.

The pore distribution of the aggregate is preferably unimodal, and bimodal having a plurality of peaks is not preferable.
Here, the reason why the aggregate pore distribution is preferably unimodal is that the pore distribution is a unimodal normal distribution, which reduces the amount of coarse voids inside the aggregate. The volume density of the aggregate is made uniform, so that the amount of the aromatic carbon compound vaporized from the inside of the aggregate is made uniform, and thus the carbonaceous material supported on the surface of the electrode active material in the aggregate. This is because the unevenness of the carrying amount of the film is reduced.

Carbon particles are preferred as the conductive assistant contained in the aggregate.
The content of the conductive auxiliary agent in the aggregate is preferably 0.3% by mass or more and 3.0% by mass or less, more preferably 0.4% by mass with respect to the Li _x A _y D _z PO ₄ particles. It is above and 2.5 mass% or less, More preferably, it is 0.6 mass% or more and 2.0 mass% or less.
Here, the reason why the content of the conductive auxiliary agent inside the aggregate is limited to the above range is that this range is a range in which the direct current resistance (DCR) is reduced without impairing the lithium ion conductivity. .

  If the content of the conductive assistant is less than 0.3% by mass, the content of the conductive assistant in the aggregate is too small, and the electronic conductivity of the aggregate is lowered. When the content of the agent exceeds 3.0% by mass, the content of the conductive auxiliary agent in the aggregate is too large, and this conductive auxiliary agent becomes an obstacle and decreases the conductivity of lithium ions. As a result, the high-rate characteristic is lowered, and particularly the direct current resistance (DCR) is significantly increased.

The reason why the direct current resistance (DCR) can be reduced by containing the carbon particles in the agglomerate as described above can be estimated as follows.
That is, by containing carbon particles inside the aggregate, the aromatic carbon compound vaporized from the inside of the aggregate is preferentially decomposed and carbonized on the surface of the carbon particles, so that the surface of the electrode active material particles The decomposition of the aromatic carbon compound and the formation of the carbonaceous film are restricted, resulting in a thin and low-density carbonaceous film. Thereby, the lithium ion conductivity in a carbonaceous film improves, As a result, it is thought that direct current | flow resistance (DCR) can be reduced.

The carbon particles are preferably particles having an average primary particle diameter of 50 nm or less, and more preferably 40 nm or less. Here, the reason why the average primary particle diameter of the carbon particles is 50 nm or less is that the aromatic carbon compound is easily decomposed on the surface of the carbon particles.
When the average primary particle diameter of the carbon particles exceeds 50 nm, the specific surface area of the carbon particles is reduced, and the aromatic carbon compound is hardly decomposed. Moreover, there is no restriction | limiting in particular about the minimum of the average primary particle diameter of this carbon particle.

  Examples of such carbon particles include thermal black, furnace black, lamp black, acetylene black, ketjen black, carbon nanotubes that are fibrous carbon, and vapor-grown carbon fibers. Particularly preferred carbon particles having excellent conductivity are acetylene black and ketjen black. Acetylene black and ketjen black are preferred because they are readily available.

  This conductive auxiliary agent is preferably contained in the aggregate as an aggregate of conductive auxiliary agent particles. The reason why the conductive auxiliary agent particle aggregate is preferable is that such a bulky conductive auxiliary agent particle aggregate is included, so that the permeability (wetting property) of the electrolyte is improved and the lithium ion diffusibility is improved. As a result, the direct current resistance (DCR) can be reduced.

The content of iron (Fe) in the conductive additive is 0.1% by mass or more and 10.0% by mass or less, and the content of phosphorus (P) is 0.1% by mass or more and 10.0% by mass or less, The content of oxygen (O) is preferably 0.1% by mass or more and 10.0% by mass or less.
Here, the reason why the contents of iron (Fe), phosphorus (P), and oxygen (O) are limited to the above range is that this range is a range in which the electronic conductivity is improved without impairing the lithium ion conductivity. That's why.

When this electrode material is evaluated, a method is used in which a 2032 type coin type cell having an electrode film thickness of 60 μm is used and the internal resistance of this electrode material is measured by a current pause method. The internal resistance thus obtained is preferably 20Ω or less.
Here, the reason why the internal resistance is limited to 20Ω or less is that when the internal resistance exceeds 20Ω, it is necessary to reduce the internal resistance as a battery by reducing the electrode film thickness. This is because the capacity decreases, and as a result, the number of electrodes must be increased in order to achieve a desired battery capacity in the battery.
Increasing the number of electrodes is not preferable because the number of electrode members such as current collectors and separators having no battery activity increases according to the number of electrodes, resulting in a decrease in battery capacity.

[Method for producing electrode material]
The manufacturing method of the electrode material of the present embodiment is performed when the above Li _x A _y D _z PO ₄ particles or a precursor thereof, an organic compound, and a conductive additive are dissolved or dispersed in a solvent, or after being dissolved or dispersed. subjected to mechanochemical treatment followed by spray-drying, comprising the Li _x a _y D _z PO ₄ carbon coated electrode active material particles to the surface of the particles comprising an electrically conducting additive comprising coated by carbonaceous coating film This is a method for obtaining an aggregate.

Next, this manufacturing method will be described in detail.
First, the above Li _x A _y D _z PO ₄ particles or a precursor thereof, an organic compound, and a conductive additive are dissolved or dispersed in a solvent to form a uniform slurry. It is even better to add a dispersant during the dissolution or dispersion.
The _Li x _A y _D z PO ₄ particles or precursors thereof described above may be any one which in the last step the _Li x _A y _D z PO ₄ particles, it is not particularly limited.

Examples of the _Li x _A y _D z PO ₄ particles, similar to that described in the above electrode _{material, Li x A y D z PO} 4 ( where, A is Co, Mn, Ni, Fe, Cu, Cr One or more selected from the group of: 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, preferably 0 <x ≦ 2, 0 <y ≦ 1, 0 ≦ z ≦ 1.5).

Here, for A, Co, Mn, Ni, and Fe are preferable, and for D, Mg, Ca, Sr, Ba, Ti, Zn, and Al are preferable because a high discharge potential is easily obtained.
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 phosphate 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 particles) can be preferably used.

The Li _x A _y D _z PO ₄ powder may be crystalline particles or amorphous particles, or may be mixed crystal particles in which crystalline particles and amorphous particles coexist. Here, the reason that the Li _x A _y D _z PO ₄ powder may be amorphous particles is that the amorphous Li _x A _y D _z PO ₄ powder is 500 ° C. or more and 1000 ° C. or less. This is because crystallization occurs when heat-treated in a non-oxidizing atmosphere.

The size of the Li _x A _y D _z PO ₄ particles is not particularly limited, but the average particle size is preferably 0.01 μm or more and 20 μm or less, more preferably 0.02 μm or more and 5 μm or less.
Here, the reason why the size of the Li _x A _y D _z PO ₄ particles, that is, the electrode active material particles (primary particles) is in the above range is that when the average particle size of the electrode active material particles is less than 0.01 μm, When the surface of the electrode active material particles is coated with a carbonaceous film, it becomes difficult to sufficiently coat with a thin film of carbon, the discharge capacity in high-speed charge / discharge is reduced, and sufficient charge / discharge performance can be realized. On the other hand, if the average particle diameter of the electrode active material particles exceeds 20 μm, the internal resistance of the electrode active material particles themselves increases and the discharge capacity in high-speed charge / discharge becomes insufficient. is there.

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

  The shape of the electrode active material particles is not particularly limited. The shape of the electrode active material particles is often characterized by the production method. For example, spherical particles are easily obtained by the solid phase method, and rectangular particles and rod-like particles are easily obtained by the hydrothermal synthesis method. Here, the spherical particles are excellent in packing properties, the rectangular particles are excellent in lithium ion insertion / release reactivity, and the rod-shaped particles are excellent in electronic conductivity because they are easily contacted between the particles. Therefore, these spherical particles, rectangular particles and rod-shaped particles may be used alone or in combination of two or more so as to satisfy the required electrical characteristics. Good. The shape of the electrode material formed by agglomerating the carbon-coated electrode active material particles obtained by coating the surfaces of the electrode active material particles with a carbonaceous film is preferably spherical, particularly true spherical.

  The reason why the shape of the electrode material is preferably spherical, and particularly true spherical, is that the electrode material, the binder resin (binder), the solvent, The amount of the solvent can be reduced when preparing the electrode (positive electrode) preparation paste by mixing the electrode and the electrode (positive electrode) preparation paste can be easily applied to the current collector. is there. Further, 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 to the electrode material can be suppressed to a minimum. This electrode (positive electrode) This is because the internal resistance of the electrode (positive electrode) obtained using the preparation paste can be reduced. Furthermore, since it is easy to close-pack, it is possible to provide a high-capacity lithium ion battery because the amount of electrode material filled per unit volume increases and the electrode density can be increased.

The organic compound is not particularly limited as long as it is an organic compound capable of forming a carbonaceous film on the surface of Li _x A _y D _z PO ₄ particles, that is, electrode active material particles (primary particles). For example, 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, polyether, polyhydric alcohol, etc. The

Examples of the polyhydric alcohol include polyethylene glycol, polypropylene glycol, polyglycerin, glycerin and the like. These may be used alone or in combination of two or more.
Examples of the conductive assistant include carbon particles such as acetylene black and ketjen black. These may be used alone or in combination of two or more. Moreover, you may add fine carbon fibers, such as a carbon nanotube (CNT), fibrous carbon, and VGCF (brand name: Showa Denko KK make).

  The solvent is preferably water, but in addition to water, for example, alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol: IPA), 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), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether Ethers such as tellurium, acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), ketones such as acetylacetone and cyclohexanone, amides such as dimethylformamide, N, N-dimethylacetoacetamide and N-methylpyrrolidone, ethylene glycol And glycols such as diethylene glycol and propylene glycol. These may be used alone or in combination of two or more.

The compounding ratio of the Li _x A _y D _z PO ₄ particles or the precursor thereof and the organic compound is based on 100 parts by mass of the Li _x A _y D _z PO ₄ particles when the total amount of the organic compound is converted into the amount of carbon. It is preferably 0.6 parts by mass or more and 4.0 parts by mass or less, more preferably 1.1 parts by mass or more and 1.7 parts by mass or less.
Here, when the compounding ratio in terms of carbon amount of the organic compound is less than 0.6 parts by mass, when the battery is formed, the discharge capacity at the high-speed charge / discharge rate is low, and it is difficult to realize sufficient charge / discharge rate performance. It becomes. On the other hand, when the compounding ratio in terms of carbon amount of the organic compound exceeds 4.0 parts by mass, when lithium ions diffuse in the carbonaceous film, the lithium ion transfer resistance increases due to steric hindrance, and as a result, the battery When formed, the internal resistance of the battery increases, and the voltage drop at the high speed charge / discharge rate cannot be ignored.

The compounding ratio of the Li _x A _y D _z PO ₄ particles or the precursor thereof to the conductive auxiliary agent is such that the conductive auxiliary agent is 0.3 mass% or more and 3.0 mass% with respect to the Li _x A _y D _z PO ₄ particles. % Or less, more preferably 0.4% by mass or more and 2.0% by mass or less.
Here, when the conductive assistant is less than 0.3% by mass, the discharge capacity at the high-speed charge / discharge rate of the Li _x A _y D _z PO ₄ particles becomes low, and it becomes difficult to realize sufficient charge / discharge rate performance. . On the other hand, if the conductive auxiliary exceeds 3.0% by mass, when lithium ions diffuse in the carbonaceous film, the lithium ion migration resistance increases due to steric hindrance. As a result, when the battery is formed, The internal resistance increases, and the voltage drop at the high speed charge / discharge rate cannot be ignored.

As a method of dissolving or dispersing Li _x A _y D _z PO ₄ particles or a precursor thereof, an organic compound, and a conductive additive in a solvent, a mechanochemical treatment can be performed when these are dissolved or dispersed. Any method may be used. For example, using a dispersing device such as a planetary ball mill, a vibration ball mill, a bead mill, a paint shaker, an attritor, etc., Li _x A _y D _z PO ₄ particles or a precursor thereof, an organic compound, and a conductive auxiliary agent are used. It is preferable to perform a mechanochemical treatment.

During the dissolution or dispersion is to disperse the Li _x A _y D _z PO ₄ particles or a precursor thereof as the primary particles, after which the organic compound was dissolved by adding, further added conductive auxiliary agent uniformly It is preferable to stir so as to disperse. In this way, the surface of the Li _x A _y D _z PO ₄ particle or its precursor is coated with an organic compound, and the Li _x A _y D _z PO ₄ particle or its precursor is impregnated with the conductive assistant. and, as a _{result, Li x a y D z PO} 4 particles or together with the carbon derived from the organic compound is uniformly interposed between the precursors _{thereof, Li x a y D z PO} 4 particles or conductive in its precursor A slurry containing the auxiliaries is obtained.

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 600 ° C. or higher and 1000 ° C. or lower, preferably 700 ° 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 600 ° C. or more and 1000 ° C. or less is that when the heat treatment temperature is less than 600 ° 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., the composition of Li _x A _y D _z PO ₄ particles constituting the electrode active material, for example, lithium (Li) evaporates to cause a deviation in composition, and Li _x A _y D grain growth of _z PO ₄ particles are accelerated, the discharge capacity in the high-speed charge and discharge rate is low, it is difficult to realize a sufficient charge and 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 Li _x A _y D _z PO ₄ particles, the precursor of the Li _x A _y D _z PO ₄ particles undergoes a chemical reaction by heat treatment to cause Li _x A _y D. becomes _z PO ₄ particles, whereas, the organic compounds are decomposed and react to produce carbon during the heat treatment, the carbon forms a carbonaceous coating adhered to the surface of the Li _x a _y D _z PO ₄ particles . _Thus, the surface of the Li _x A _y D z PO ₄ particles and thus covered by carbonaceous coating.
The conductive auxiliary _agent, Li _x A _y D z PO by ₄ precursor particles heat treated in the _Li x _A y _D z PO ₄ particles by chemical reaction, _Li x _A y _D z PO for this product ₄ particles are impregnated.

Here, since Li _x A _y D _z PO ₄ particles contain lithium, as the heat treatment time becomes longer, lithium diffuses from the Li _x A _y D _z PO ₄ particles into the carbonaceous film, and the inside of the carbonaceous film This is preferable because lithium is present in the carbon and the conductivity of the carbonaceous film is further improved.
However, if the heat treatment time becomes too long, abnormal grain growth occurs or Li _x A _y D _z PO ₄ particles partially lacking lithium are generated, so that the Li _x A _y D _z PO ₄ particles themselves The performance is lowered, and as a result, the battery characteristics using the carbonaceous coated electrode active material particles are deteriorated.
Thus, it is possible to obtain an aggregate consisting of Li _x A _y D _z PO ₄ carbon coated electrode active material particles to the surface of the particles comprising an electrically conducting additive comprising coated by carbonaceous coating film.

[electrode]
The electrode of the present embodiment is an electrode containing 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.

  The solvent used for the electrode-forming paint or electrode-forming paste may be appropriately selected according to the properties of the binder resin. For example, water, methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol: IPA) , Butanol, pentanol, hexanol, octanol, diacetone alcohol and other 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 monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl celloso) B), 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 -Amides such as 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 includes a positive electrode made of the electrode of this embodiment, a negative electrode made of metal Li, Li alloy, Li ₄ Ti ₅ O ₁₂ , a carbon material, etc., and an electrolyte solution and a separator or a solid electrolyte. Yes.
In this lithium ion battery, when an electrode is produced using the electrode material of the present embodiment, the desorption / insertion of Li becomes good, and thus high stability can be realized.
Moreover, the electronic conductivity of the electrode can be improved. Therefore, high-rate characteristics can be improved, and particularly direct current resistance (DCR) can be greatly reduced.

As described above, according to the electrode material of the present embodiment, the BET value of an aggregate composed of carbonaceous coated electrode active material particles obtained by coating the surface of Li _x A _y D _z PO ₄ particles with a carbonaceous film. Is 8 m ² / g or more and 40 m ² / g or less, the average pore is 0.5 μm or less, the pore distribution is unimodal, and the conductive auxiliary agent is incorporated in the aggregate inside the Li _x A _y D _z PO _4. Since 0.3 mass% or more and 3.0 mass% or less were contained with respect to particle | grains, electronic conductivity can be improved, without impairing the conductivity of lithium ion. Therefore, high-rate characteristics can be improved, and particularly direct current resistance (DCR) can be greatly reduced.

According to the method for producing an electrode material of the present embodiment, Li _x A _y D _z PO ₄ particles or a precursor thereof, an organic compound, and a conductive additive are dissolved or dispersed in a solvent, or after being dissolved or dispersed. By applying a mechanochemical treatment, and then spraying and drying, a coagulant composed of carbonaceous coated electrode active material particles containing a conductive assistant formed by coating the surface of Li _x A _y D _z PO ₄ particles with a carbonaceous coating. Since the aggregate is obtained, it is possible to easily and inexpensively manufacture an electrode material that can improve high-rate characteristics, and in particular, can greatly reduce direct current resistance (DCR).

  According to the electrode of the present embodiment, since the electrode material of the present embodiment is contained, high rate characteristics can be improved, and in particular, direct current resistance (DCR) can be greatly reduced.

  According to the lithium ion battery of the present embodiment, since the positive electrode comprising the electrode of the present embodiment is provided, the high-rate characteristics are improved, and in particular, the direct current resistance (DCR) is greatly reduced, and the durability is good. The discharge capacity at a high speed charge / discharge rate is high, and sufficient charge / discharge rate performance can be obtained.

EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-15 and Comparative Examples 1-3, this invention is not limited by 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.

"Example 1"
(Production of electrode material)
4 mol of lithium acetate (LiCH ₃ COO), 2 mol of iron (II) sulfate (FeSO ₄ ), and 2 mol of phosphoric acid (H ₃ PO ₄ ) were mixed with 2 L (liter) of water so that the total amount was 4 L. Thus, a uniform slurry mixture was prepared.
Subsequently, this mixture was accommodated in a pressure-resistant sealed container having a capacity of 8 L, and hydrothermal synthesis was performed at 120 ° C. for 1 hour.
Next, the obtained precipitate was washed with water to obtain a cake-like electrode active material precursor.

  Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material 0.4 mass% was mixed with 500 g of zirconia balls having a diameter of 5 mm, and mechanochemical treatment was performed together with dispersion treatment for 12 hours in a 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. An electrode material (A1) of Example 1 was obtained.

(Evaluation of electrode material)
The volume density and BET value of this electrode material (A1) were evaluated.
The evaluation method is as follows.
(1) Volume density Using a mercury porosimeter, the volume density (%) of the electrode material (A1) was calculated from the mass of the entire electrode material (A1) and the volume of the gap between the particles of the electrode material (A1).
(2) Specific surface area (BET value)
The BET value of the electrode material (A1) was measured by BELSORP-mini using nitrogen (N ₂ ) adsorption.
As a result, the volume density of the electrode material (A1) was 49%, and the BET value was 12.5 m ² / g.

When this electrode material (A1) was observed with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), a plurality of LiFePO ₄ particles (primary particles) were aggregated to form aggregates, and these The surface of the LiFePO ₄ particles was covered with a thin film-like carbonaceous film, and it was observed that carbon was interposed between the LiFePO ₄ particles.

(Production of lithium ion battery)
The electrode material (A1), polyvinylidene fluoride (PVdF) as a binder, and acetylene black (AB) as a conductive additive are mixed so that the mass ratio is 90: 5: 5, and further N as a solvent. -Methyl-2-pyrrolidinone (NMP) was added to impart fluidity to produce a slurry.
Next, this slurry was applied onto an aluminum (Al) foil having a thickness of 15 μm and dried. Then, it pressurized by the pressure of 600 kgf / cm < ² >, and the positive electrode of the lithium ion battery of Example 1 was produced.

Lithium metal was disposed as a negative electrode with respect to the positive electrode of the lithium ion battery, and a separator made of porous polypropylene was disposed between the positive electrode and the negative electrode to obtain a battery member.
On the other hand, lithium hexafluorophosphate (LiPF) was added to a mixed solution in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 1 so as to have a concentration of 1 mol / dm ³ . ₆ ) was dissolved to prepare a non-aqueous electrolyte solution.
Next, the battery member was immersed in the nonaqueous electrolyte solution, and a lithium ion battery of Example 1 was produced.

(Evaluation of lithium-ion battery)
For the above lithium ion battery, after charging at an environmental temperature of 25 ° C. and 0.1% SOC at 50% SOC, as the first cycle, “1C charge 10 seconds → pause 10 minutes → 1C discharge 10 seconds → pause 10 minutes” The second cycle is “3C charge 10 seconds → pause 10 minutes → 3C discharge 10 seconds → pause 10 minutes”, and the third cycle is “5C charge 10 seconds → pause 10 minutes → 5C discharge 10 seconds → pause 10 minutes” As the fourth cycle, “10C charging for 10 seconds → pause 10 minutes → 10C discharge for 10 seconds → pause 10 minutes” is carried out in this order, and each charge and discharge at that time is based on the values after 10 seconds. An approximate curve was drawn, and the slopes of the straight lines in the approximate curve were defined as the DC resistance (input DCR) on the input side and the DC resistance (output DCR) on the output side, respectively.
As a result, the input DCR was 8.0Ω, the output DCR was 7.2Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 90%.

"Example 2"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material 0.8 mass% was mixed with 500 g of zirconia balls having a diameter of 5 mm, and mechanochemical treatment was performed together with dispersion treatment for 12 hours in a 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. An electrode material (A2) of Example 2 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A2) were performed according to Example 1. As a result, the volume density of the electrode material (A2) was 48%, and the BET value was 12.7 m ² / g.
Using this electrode material (A2), a lithium ion battery of Example 2 was produced according to Example 1 and evaluated.
As a result, the input DCR was 7.9Ω, the output DCR was 7.3Ω, the initial capacity was 157 mAh / g, and the rate rate (3C / 0.1C) was 91%.

FIG. 1 is a scanning transmission electron microscope (STEM) image showing an electrode produced using the electrode material (A2) of Example 2, in which “001” and “002” are energy dispersive X-ray spectroscopy ( EDX) shows the location where the surface analysis was performed.
FIG. 2 is a view showing a surface analysis result by EDX at an analysis location “001” of an electrode manufactured using the electrode material (A2) of Example 2, and FIG. 3 is an analysis of “002” of the electrode. It is a figure which shows the surface analysis result by EDX in a location.
These surface analysis results are shown in Table 1.

According to these figures and Table 1, it can be seen that trace amounts of components derived from the electrode active material are detected on the surface of the conductive additive. This is thought to be due to the fact that part of the conductive auxiliary and part of the electrode active material were integrated because the mechanochemical treatment was performed when the electrode active material and the conductive auxiliary were dispersed. It is considered that the integration improves the conductivity, and the direct current resistance (DCR) is greatly reduced.
Moreover, it turns out that the conductive support agent particle is contained in the space | gap of an electrode material as an aggregate. By including such a bulky conductive auxiliary agent particle aggregate, the permeability (wetting property) of the electrolytic solution is improved, and the conductive auxiliary agent particles preferentially decompose the aromatic carbon compound inside the electrode material. Therefore, the carbonaceous film on the surface of the active material particles is adjusted, and the ionic conductivity is improved. As a result, the direct current resistance (DCR) is considered to be greatly reduced.

"Example 3"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material 1.2% by mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment for 12 hours in a 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. An electrode material (A3) of Example 3 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A3) were performed according to Example 1. As a result, the volume density of the electrode material (A3) was 47.5%, and the BET value was 12.8 m ² / g.
Using this electrode material (A3), a lithium ion battery of Example 3 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.2Ω, the output DCR was 7.1Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 91%.

Example 4
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material 2.0 mass% was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment for 12 hours in a 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. The electrode material (A4) of Example 4 was obtained.

(Evaluation)
The volume density and BET value of this electrode material (A4) and the respective evaluations were performed according to Example 1. As a result, the volume density of the electrode material (A4) was 46%, and the BET value was 12.9 m ² / g.
Using this electrode material (A4), a lithium ion battery of Example 4 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.5Ω, the output DCR was 7.7Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 89%.

"Example 5"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material Then, 3.0% by mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment together with dispersion treatment for 12 hours in a 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. An electrode material (A5) of Example 5 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A5) were performed according to Example 1. As a result, the volume density of the electrode material (A5) was 45.2%, and the BET value was 13.2 m ² / g.
Using this electrode material (A5), a lithium ion battery of Example 5 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.5Ω, the output DCR was 7.5Ω, the initial capacity was 157 mAh / g, and the rate rate (3C / 0.1C) was 89%.

"Example 6"
(Production of electrode material)
4 mol of lithium acetate (LiCH ₃ COO), 2 mol of iron (II) sulfate (FeSO ₄ ), and 2 mol of phosphoric acid (H ₃ PO ₄ ) were mixed with 2 L (liter) of water so that the total amount was 4 L. Then, dilute sulfuric acid was added to adjust to pH = 2.5, and a uniform slurry mixture having a pH lower than that of the slurry mixture of Example 1 was prepared.
Subsequently, this mixture was accommodated in a pressure-resistant sealed container having a capacity of 8 L, and hydrothermal synthesis was performed at 120 ° C. for 1 hour.
Next, the obtained precipitate was washed with water to obtain a cake-like electrode active material precursor.

  Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material 1.0% by mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment in a ball mill for 12 hours 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. An electrode material (A6) of Example 6 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A6) were performed according to Example 1. As a result, the volume density of the electrode material (A6) was 49.5%, and the BET value was 8.3 m ² / g.
Using this electrode material (A6), a lithium ion battery of Example 6 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.9Ω, the output DCR was 7.9Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 86%.

"Example 7"
(Production of electrode material)
4 mol of lithium acetate (LiCH ₃ COO), 2 mol of iron (II) sulfate (FeSO ₄ ), and 2 mol of phosphoric acid (H ₃ PO ₄ ) were mixed with 2 L (liter) of water so that the total amount was 4 L. Next, dilute sulfuric acid was added to adjust to pH = 3.0 to prepare a uniform slurry mixture having a pH lower than that of the slurry mixture of Example 1.
Subsequently, this mixture was accommodated in a pressure-resistant sealed container having a capacity of 8 L, and hydrothermal synthesis was performed at 120 ° C. for 1 hour.
Next, the obtained precipitate was washed with water to obtain a cake-like electrode active material precursor.

  Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material 1.0% by mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment in a ball mill for 12 hours 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. An electrode material (A7) of Example 7 was obtained.

(Evaluation)
The volume density and BET value of this electrode material (A7) and the respective evaluations were performed according to Example 1. As a result, the volume density of the electrode material (A7) was 47.6%, and the BET value was 10.5 m ² / g.
Using this electrode material (A7), a lithium ion battery of Example 7 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.2Ω, the output DCR was 7.4Ω, the initial capacity was 157 mAh / g, and the rate rate (3C / 0.1C) was 87%.

"Example 8"
(Production of electrode material)
4 mol of lithium acetate (LiCH ₃ COO), 2 mol of iron (II) sulfate (FeSO ₄ ), and 2 mol of phosphoric acid (H ₃ PO ₄ ) were mixed with 2 L (liter) of water so that the total amount was 4 L. Then, ammonia water was added to adjust to pH = 4.0 to prepare a uniform slurry mixture having a pH higher than that of the slurry mixture of Example 1.
Subsequently, this mixture was accommodated in a pressure-resistant sealed container having a capacity of 8 L, and hydrothermal synthesis was performed at 120 ° C. for 1 hour.
Next, the obtained precipitate was washed with water to obtain a cake-like electrode active material precursor.

  Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material 1.0% by mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment in a ball mill for 12 hours 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. The electrode material (A8) of Example 8 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A8) were performed according to Example 1. As a result, the volume density of the electrode material (A8) was 46.2%, and the BET value was 13.8 m ² / g.
Using this electrode material (A8), a lithium ion battery of Example 8 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.0Ω, the output DCR was 7.2Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 89%.

"Example 9"
(Production of electrode material)
4 mol of lithium acetate (LiCH ₃ COO), 2 mol of iron (II) sulfate (FeSO ₄ ), and 2 mol of phosphoric acid (H ₃ PO ₄ ) were mixed with 2 L (liter) of water so that the total amount was 4 L. Then, ammonia water was added to adjust the pH to 4.5, and a uniform slurry mixture having a pH higher than that of the slurry mixture of Example 1 was prepared.
Subsequently, this mixture was accommodated in a pressure-resistant sealed container having a capacity of 8 L, and hydrothermal synthesis was performed at 120 ° C. for 1 hour.
Next, the obtained precipitate was washed with water to obtain a cake-like electrode active material precursor.

  Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass of the above electrode active material precursor converted to the electrode active material 1.0% by mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment in a ball mill for 12 hours 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and further, acetylene black was impregnated into the LiFePO ₄ particles. An electrode material (A9) of Example 9 was obtained.

(Evaluation)
The volume density and BET value of the electrode material (A9) were evaluated in accordance with Example 1. As a result, the volume density of the electrode material (A9) was 45.8%, and the BET value was 14.8 m ² / g.
Using this electrode material (A9), a lithium ion battery of Example 9 was produced according to Example 1 and evaluated.
As a result, the input DCR was 7.9Ω, the output DCR was 7.1Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 92%.

"Example 10"
(Production of electrode material)
4 mol of lithium acetate (LiCH ₃ COO), 2 mol of manganese (II) sulfate (MnSO ₄ ), and 2 mol of phosphoric acid (H ₃ PO ₄ ) were mixed in 2 L (liter) of water so that the total amount was 4 L. Then, ammonia water was added to adjust the pH to 4.5, and a uniform slurry mixture having a pH higher than that of the slurry mixture of Example 1 was prepared.
Subsequently, this mixture was accommodated in a pressure-resistant sealed container having a capacity of 8 L, and hydrothermal synthesis was performed at 120 ° C. for 1 hour.
Next, the obtained precipitate was washed with water to obtain a cake-like electrode active material precursor.

Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, lithium acetate (LiCH ₃ COO) and ferrous acetate (Fe (CH ₃ COO) ₂ ) as the catalyst And diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) in terms of LiMnPO ₄ , 6.3 g, and acetylene black as a conductive additive in terms of the above electrode active material precursor in terms of electrode active material 0.8% by mass with respect to the obtained mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment for 12 hours in a 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 baked for 1 hour in a nitrogen (N ₂ ) gas atmosphere at 700 ° C., the surface of LiMnPO ₄ particles was covered with a carbonaceous film, and acetylene black was impregnated into the LiMnPO ₄ particles. An electrode material (A10) of Example 10 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A10) were performed according to Example 1. As a result, the volume density of the electrode material (A10) was 45.1%, and the BET value was 30.8 m ² / g.
Using this electrode material (A10), a lithium ion battery of Example 10 was produced according to Example 1 and evaluated.
As a result, the input DCR was 28.0Ω, the output DCR was 23.1Ω, the initial capacity was 153 mAh / g, and the rate rate (3C / 0.1C) was 89%.

"Example 11"
(Production of electrode material)
4 mol of lithium acetate (LiCH ₃ COO), 2 mol of manganese (II) sulfate (MnSO ₄ ), and 2 mol of phosphoric acid (H ₃ PO ₄ ) were mixed in 2 L (liter) of water so that the total amount was 4 L. Then, ammonia water was added to adjust to pH = 5.5, and a uniform slurry mixture having a pH higher than that of the slurry mixture of Example 10 was prepared.
Subsequently, this mixture was accommodated in a pressure-resistant sealed container having a capacity of 8 L, and hydrothermal synthesis was performed at 120 ° C. for 1 hour.
Next, the obtained precipitate was washed with water to obtain a cake-like electrode active material precursor.

Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, lithium acetate (LiCH ₃ COO) and ferrous acetate (Fe (CH ₃ COO) ₂ ) as the catalyst And diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) in terms of LiMnPO ₄ , 6.3 g, and hydrophilic acetylene black surface-treated with carboxylic acid as a conductive assistant as an aqueous dispersion The above electrode active material precursor is mixed with 500 g of zirconia balls having a diameter of 5 mm with respect to the mass of the electrode active material converted into the electrode active material, and is mechanochemically treated with a ball mill for 12 hours. 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 baked for 1 hour in a nitrogen (N ₂ ) gas atmosphere at 700 ° C., the surface of LiMnPO ₄ particles was covered with a carbonaceous film, and acetylene black was impregnated into the LiMnPO ₄ particles. An electrode material (A11) of Example 11 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A11) were performed according to Example 1. As a result, the volume density of the electrode material (A11) was 44.1%, and the BET value was 39.2 m ² / g.
Using this electrode material (A11), a lithium ion battery of Example 11 was produced according to Example 1 and evaluated.
As a result, the input DCR was 21.2Ω, the output DCR was 19.0Ω, the initial capacity was 154 mAh / g, and the rate rate (3C / 0.1C) was 90%.

"Example 12"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, and Ketjen black as the conductive auxiliary agent were converted into the electrode active material from the above electrode active material precursor. 0.5% by mass with respect to the mass was mixed with 500 g of zirconia balls having a diameter of 5 mm, and mechanochemical treatment was performed together with dispersion treatment for 12 hours in a 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 calcined for 1 hour in a nitrogen (N ₂ ) gas atmosphere at 700 ° C., the surface of LiFePO ₄ particles was covered with a carbonaceous film, and ketjen black was further added to the LiFePO ₄ particles. An impregnated electrode material (A12) of Example 12 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A12) were performed according to Example 1. As a result, the volume density of the electrode material (A12) was 49.5%, and the BET value was 12.7 m ² / g.
Using this electrode material (A12), a lithium ion battery of Example 12 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.9Ω, the output DCR was 7.7Ω, the initial capacity was 159 mAh / g, and the rate rate (3C / 0.1C) was 91%.

"Example 13"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, and Ketjen black as the conductive auxiliary agent were converted into the electrode active material from the above electrode active material precursor. 1.0 mass% with respect to the mass was mixed with 500 g of zirconia balls having a diameter of 5 mm, and a mechanochemical treatment was performed together with a dispersion treatment in a ball mill for 12 hours 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 calcined for 1 hour in a nitrogen (N ₂ ) gas atmosphere at 700 ° C., the surface of LiFePO ₄ particles was covered with a carbonaceous film, and ketjen black was further added to the LiFePO ₄ particles. The impregnated electrode material (A13) of Example 13 was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A13) were performed according to Example 1. As a result, the volume density of the electrode material (A13) was 49.2%, and the BET value was 12.9 m ² / g.
Using this electrode material (A13), a lithium ion battery of Example 13 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.7Ω, the output DCR was 7.8Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 90%.

"Example 14"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, and Ketjen black as the conductive auxiliary agent were converted into the electrode active material from the above electrode active material precursor. 2.0% by mass with respect to the mass was mixed with 500 g of zirconia balls having a diameter of 5 mm, and a mechanochemical treatment was performed together with a dispersion treatment for 12 hours in a 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 calcined for 1 hour in a nitrogen (N ₂ ) gas atmosphere at 700 ° C., the surface of LiFePO ₄ particles was covered with a carbonaceous film, and ketjen black was further added to the LiFePO ₄ particles. An impregnated electrode material (A14) of Example 14 was obtained.

(Evaluation)
The volume density and BET value of the electrode material (A14) and the respective evaluations were performed according to Example 1. As a result, the volume density of the electrode material (A14) was 47.3%, and the BET value was 13.2 m ² / g.
Using this electrode material (A14), a lithium ion battery of Example 14 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.7Ω, the output DCR was 7.8Ω, the initial capacity was 157 mAh / g, and the rate rate (3C / 0.1C) was 91%.

"Example 15"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, and Ketjen black as the conductive auxiliary agent were converted into the electrode active material from the above electrode active material precursor. 3.0% by mass with respect to the mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment for 12 hours in a 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 calcined for 1 hour in a nitrogen (N ₂ ) gas atmosphere at 700 ° C., the surface of LiFePO ₄ particles was covered with a carbonaceous film, and ketjen black was further added to the LiFePO ₄ particles. An impregnated electrode material (A15) of Example 15 was obtained.

(Evaluation)
The volume density and BET value of the electrode material (A15) and the respective evaluations were performed according to Example 1. As a result, the volume density of the electrode material (A15) was 46.9%, and the BET value was 13.7 m ² / g.
Using this electrode material (A15), a lithium ion battery of Example 15 was produced according to Example 1 and evaluated.
As a result, the input DCR was 8.8Ω, the output DCR was 7.5Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 87%.

"Example 16"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, carbon nanotubes (CNT) as the conductive assistant, and the precursor of the above electrode active material as the electrode active material 0.8% by mass with respect to the converted mass was mixed with 500 g of zirconia balls having a diameter of 5 mm and subjected to mechanochemical treatment with a dispersion treatment for 12 hours in a 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour, the surface of LiFePO ₄ particles was covered with a carbonaceous film, and carbon nanotubes (CNTs) were further formed in the LiFePO ₄ particles. ) Was impregnated to obtain an electrode material (A16) of Example 16.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A16) were performed according to Example 1. As a result, the volume density of the electrode material (A16) was 48.8%, and the BET value was 12.6 m ² / g.
Using this electrode material (A16), a lithium ion battery of Example 16 was produced according to Example 1 and evaluated.
As a result, the input DCR was 9.1Ω, the output DCR was 7.6Ω, the initial capacity was 159 mAh / g, and the rate rate (3C / 0.1C) was 88%.

"Example 17"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, and fine carbon fiber (VGCF: trade name, manufactured by Showa Denko KK) as the conductive auxiliary agent are used as the above electrodes. 0.8% by mass with respect to the mass of the active material precursor converted to the electrode active material is mixed with 500 g of zirconia balls having a diameter of 5 mm, and subjected to mechanochemical treatment together with dispersion treatment for 12 hours in a ball mill. A suitable slurry was prepared.

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 resulting granular material to 700 ° C. in a nitrogen _{(N 2)} and baked for one hour under atmosphere, covers the surface of the LiFePO ₄ particles carbonaceous coating further fine carbon fibers in the LiFePO ₄ within the particle ( The electrode material (A17) of Example 17 impregnated with (VGCF) was obtained.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (A17) were performed according to Example 1. As a result, the volume density of the electrode material (A17) was 48.1%, and the BET value was 12.8 m ² / g.
Using this electrode material (A17), a lithium ion battery of Example 17 was produced in accordance with Example 1 and evaluated.
As a result, the input DCR was 8.8Ω, the output DCR was 8.0Ω, the initial capacity was 157 mAh / g, and the rate rate (3C / 0.1C) was 88%.

"Comparative Example 1"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of this electrode active material precursor (in terms of solid content) and 5.5 g of polyethylene glycol as an organic compound are mixed with 500 g of zirconia balls having a diameter of 5 mm, and subjected to a dispersion treatment for 12 hours using a ball mill. A suitable slurry was prepared.

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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour to obtain an electrode material (B1) of Comparative Example 1 in which the surface of LiFePO ₄ particles was covered with a carbonaceous film.

(Evaluation)
The volume density and BET value of the electrode material (B1) and the respective evaluations were performed according to Example 1. As a result, the volume density of the electrode material (B1) was 48.9%, and the BET value was 12.5 m ² / g.
Using this electrode material (B1), a lithium ion battery of Comparative Example 1 was produced according to Example 1 and evaluated.
As a result, the input DCR was 10.1Ω, the output DCR was 8.6Ω, the initial capacity was 157 mAh / g, and the rate rate (3C / 0.1C) was 65%.

"Comparative Example 2"
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g of the electrode active material precursor (in terms of solid content), 1.1 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass obtained by converting the above electrode active material precursor into the electrode active material 1.0% by mass was mixed with 500 g of zirconia balls having a diameter of 5 mm, and dispersion treatment was performed for 12 hours in a 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour to cover the surface of the LiFePO ₄ particles with a carbonaceous film, and the carbonaceous film LiFePO ₄ particles, acetylene black, The electrode material (B2) of Comparative Example 2 was mixed.

(Evaluation)
The volume density and BET value of the electrode material (B2) and the respective evaluations were performed according to Example 1. As a result, the volume density of the electrode material (B2) was 31.5%, and the BET value was 12.8 m ² / g.
Using this electrode material (B2), a lithium ion battery of Comparative Example 2 was produced according to Example 1 and evaluated.
As a result, the input DCR was 10.2Ω, the output DCR was 8.8Ω, the initial capacity was 157 mAh / g, and the rate rate (3C / 0.1C) was 88%.

“Comparative Example 3”
(Production of electrode material)
A cake-like electrode active material precursor was obtained according to Example 1.
Next, 150 g (in terms of solid content) of this electrode active material precursor, 22.0 g of polyethylene glycol as the organic compound, acetylene black as the conductive auxiliary agent, and the mass obtained by converting the above electrode active material precursor into the electrode active material 1.0% by mass was mixed with 500 g of zirconia balls having a diameter of 5 mm, and dispersion treatment was performed for 12 hours in a 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour to cover the surface of the LiFePO ₄ particles with a carbonaceous film, and the carbonaceous film LiFePO ₄ particles, acetylene black, The electrode material (B3) of Comparative Example 3 was mixed.

(Evaluation)
The volume density, BET value, and evaluation of this electrode material (B3) were performed in accordance with Example 1. As a result, the volume density of the electrode material (B3) was 78.5%, and the BET value was 12.4 m ² / g.
Using this electrode material (B3), a lithium ion battery of Comparative Example 3 was produced according to Example 1 and evaluated.
As a result, the input DCR was 10.5Ω, the output DCR was 8.9Ω, the initial capacity was 158 mAh / g, and the rate rate (3C / 0.1C) was 87%.

“Comparative Example 4”
A cake-like electrode active material precursor was obtained according to Example 10.
Next, 150 g of this electrode active material precursor (in terms of solid content), 5.5 g of polyethylene glycol as the organic compound, lithium acetate (LiCH ₃ COO) and ferrous acetate (Fe (CH ₃ COO) ₂ ) as the catalyst And diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), 6.3 g in terms of LiMnPO ₄ , are mixed with 500 g of zirconia balls having a diameter of 5 mm, and mechano with dispersion treatment for 12 hours in a ball mill. Chemical treatment was performed 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 in a nitrogen (N ₂ ) gas atmosphere at 700 ° C. for 1 hour to obtain an electrode material (B4) of Comparative Example 4 in which the surface of LiMnPO ₄ particles was coated with a carbonaceous film.

(Evaluation)
The volume density and BET value of the electrode material (B4) and the respective evaluations were performed according to Example 1. As a result, the volume density of the electrode material (B4) was 43.0%, and the BET value was 29.9 m ² / g.
Using this electrode material (B4), a lithium ion battery of Comparative Example 4 was produced according to Example 10 and evaluated.
As a result, the input DCR was 35.1Ω, the output DCR was 29.2Ω, the initial capacity was 150 mAh / g, and the rate rate (3C / 0.1C) was 85%.
These evaluation results are shown in Table 2.

As can be seen from Table 2, battery properties, particularly direct current resistance (DCR), are reduced by adding 0.1 to 3.0% by mass of a conductive additive in the aggregate (spherical granules) with respect to the electrode active material. It was found that excellent high rate characteristics were exhibited.
The reason is that, as already mentioned, the conductive auxiliary particles preferentially decompose the aromatic carbon compound inside the electrode material, so that the carbonaceous film on the surface of the active material particles is adjusted and the ion conductivity is improved. Conceivable.
Moreover, it is thought that the permeability (wetting property) of the electrolytic solution was improved and excellent battery characteristics were exhibited by containing a bulky conductive auxiliary agent inside the aggregate (spherical granule).
Furthermore, it is thought that the electronic conductivity inside the aggregate (spherical granules) was improved by the conductive assistant.

From the above results, LiFePO ₄ and LiMnPO ₄ containing a conductive additive in the aggregate (spherical granule) of the electrode active material can reduce the direct current resistance (DCR) and increase the rate of the secondary battery. It was possible to improve.

Electrode material of the present _{invention, Li x A y D z PO} 4 ( where, A is Co, Mn, Ni, Fe, Cu, 1 or two or more elements selected from a group consisting of Cr, D is Mg, Ca, One or more selected from the group consisting of Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, 0 <x ≦ 2, 0 <y ≦ 1 0 ≦ z ≦ 1.5) The BET value of the aggregate composed of carbonaceous coated electrode active material particles obtained by coating the surface of the particles with a carbonaceous coating is 8 m ² / g or more and 40 m ² / g or less, and the average fineness The pores are 0.5 μm or less, the pore distribution is unimodal, and the conductive auxiliary agent is 0.3% by mass or more and 3.0% by mass with respect to the Li _x A _y D _z PO ₄ particles inside the aggregate. % Or less improves electronic conductivity without impairing lithium ion conductivity Therefore, high-rate characteristics can be improved, and in particular, direct current resistance (DCR) can be greatly reduced, so that the next generation is expected to be smaller, lighter, and higher in capacity. The secondary battery can be applied to the secondary battery, and in the case of the next-generation secondary battery, the effect is very large.

Claims (7)

Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Co, Mn, Ni, Fe, Cu, Cr, 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, 0 <x ≦ 2, 0 <y ≦ 1, 0 ≦ z ≦ 1. 5) Aggregates comprising carbonaceous coated electrode active material particles obtained by coating the surface of the particles with a carbonaceous coating,
The BET value of the aggregate is 8 m ² / g or more and 40 m ² / g or less, the average pore is 0.5 μm or less, and the pore distribution is unimodal. An electrode material comprising 0.3% by mass or more and 3.0% by mass or less based on _x A _y D _z PO ₄ particles.   2. The electrode material according to claim 1, wherein a volume density of the aggregate is 35% by volume or more and 50% by volume or less of a volume density when the aggregate is solid.   The conductive auxiliary agent is carbon particles, and is contained in an aggregate composed of the carbonaceous coated electrode active material particles as a conductive auxiliary agent particle aggregate in which fine particles having an average primary particle diameter of 50 nm or less are aggregated. The electrode material according to claim 1 or 2, wherein   The iron content in the conductive assistant is 0.1% by mass to 10.0% by mass, the phosphorus content is 0.1% by mass to 10.0% by mass, and the oxygen content is 0%. The electrode material according to any one of claims 1 to 3, wherein the electrode material is not less than 1% by mass and not more than 10.0% by mass. A method for producing the electrode material according to any one of claims 1 to 4,
When the Li _x A _y D _z PO ₄ particles or a precursor thereof, an organic compound and a conductive additive are dissolved or dispersed in a solvent, or after being dissolved or dispersed, a mechanochemical treatment is performed, and then sprayed and dried. by, the Li _x a _y D _z PO electrode material characterized by obtaining an aggregate of carbon coated electrode active material particles containing ₄ surface of the particles a conductive additive formed by coating a carbonaceous coat Production method.   An electrode comprising the electrode material according to any one of claims 1 to 4.   A lithium ion battery comprising a positive electrode comprising the electrode according to claim 6.