JP2014116290A - Negative electrode material, negative electrode active material, negative electrode for lithium ion battery, and lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode material for a lithium ion battery having excellent preservation characteristics while providing an average layer surface space of a (002) plane that is larger than that of a graphite material.SOLUTION: A negative electrode material is provided for a lithium ion battery, and an average layer surface space dof a (002) plane that is calculated by an X-ray diffraction method using a CuKα ray as a radiation source is 0.340 nm or more. A chemical adsorbed water ratio A calculated by the following procedures is 0.5% or less. (1) The negative electrode material according to this embodiment is held for 120 hours under a condition that a temperature is 40°C and a relative humidity is 90%RH. (2) (A) a step of holding the negative electrode material for one hour under a condition at a temperature of 130°C and in a nitrogen atmosphere, and (B) a step of raising a temperature of the negative electrode material after the step (A) from 40°C to 540°C at 10°C/minute under the nitrogen atmosphere to measure a weight reduction amount of the negative electrode material, are sequentially performed by using a thermogravimetry measurement device to calculate the chemical adsorbed water ratio A from the following formula. The chemical adsorbed water ratio A[%]=100×(Y-Y)/X where X represents a weight of the negative electrode material after the step (A), and Yrepresents a weight of the negative electrode material at 150°C at the step (B), and Yrepresents a weight of the negative electrode material at 250°C at the step (B).

Description

  The present invention relates to a negative electrode material, a negative electrode active material, a negative electrode for a lithium ion battery, and a lithium ion battery.

As a negative electrode material for a lithium ion battery, a graphite material is generally used.
However, since the graphite material expands and contracts between the crystallite layers due to lithium doping and dedoping, the crystallites are likely to be distorted. For this reason, the graphite material is likely to break the crystal structure due to repeated charge and discharge, and the lithium ion battery using the graphite material as the negative electrode material is inferior in charge and discharge cycle characteristics.

Patent Document 1 (Japanese Patent Laid-Open No. 8-115723) discloses that helium with respect to the density (ρ _B ) measured by using butanol as a substitution medium having an average layer spacing of (002) plane of 0.365 nm or more determined by X-ray diffraction method. A carbonaceous material for a secondary battery electrode is described in which the ratio (ρ _H / ρ _B ) of density (ρ _H ) measured using gas as a replacement medium is 1.15 or more.
Such a carbonaceous material is said to have excellent charge / discharge cycle characteristics because the crystallite layer is larger than the graphite material and the crystal structure is not easily destroyed by repeated charge / discharge compared to the graphite material. (See Patent Documents 1 and 2).

JP-A-8-115723 International Publication No. 2007/040007 Pamphlet

  However, as described in Patent Documents 1 and 2, a carbonaceous material having a larger crystallite layer than a graphite material is more easily deteriorated in the atmosphere than a graphite material and has poor storage characteristics. It was. For this reason, it has been necessary to store in an inert gas atmosphere immediately after production, and it has been difficult to handle compared to a graphite material.

  Therefore, an object of the present invention is to provide a negative electrode material for a lithium ion battery having an excellent (002) plane average layer spacing as compared with a graphite material and having excellent storage characteristics.

  The present inventors diligently studied design guidelines for realizing a negative electrode material for a lithium ion battery having an average layer spacing of (002) planes larger than that of a graphite material and having excellent storage characteristics. As a result, the present inventors have found that the measure of the chemical adsorption water ratio devised by the present inventors is effective as such a design guideline, and reached the present invention.

According to the first invention of the present invention,
A negative electrode material for a lithium ion battery having a (002) plane average layer spacing d ₀₀₂ of 0.340 nm or more obtained by X-ray diffraction using CuKα rays as a radiation source and carbonizing the resin composition. There,
After holding the negative electrode material for 120 hours under conditions of a temperature of 40 ° C. and a relative humidity of 90% RH,
Using a thermogravimetric measuring device,
(A) holding the negative electrode material under conditions of a temperature of 130 ° C. and a nitrogen atmosphere for 1 hour;
(B) The step of heating the negative electrode material after the step (A) at a temperature of 10 ° C./min from a temperature of 40 ° C. to 540 ° C. in a nitrogen atmosphere, and measuring the weight loss of the negative electrode material;
In order,
The weight of the negative electrode material after the step (A) is X,
The weight of the negative electrode material at 150 ° C. in the step (B) is Y ₁ ,
When the weight of the negative electrode material at 250 ° C. in the step (B) is Y ₂ ,
Provided is a negative electrode material for a lithium ion battery having a chemical adsorption water ratio A defined by 100 × (Y ₁ -Y ₂ ) / X of 0.5% or less.

According to the second invention of the present invention,
A negative electrode material for a lithium ion battery having an average layer spacing d _{002 of} (002) planes of 0.340 nm or more determined by an X-ray diffraction method using CuKα rays as a radiation source,
After holding the negative electrode material for 120 hours under conditions of a temperature of 40 ° C. and a relative humidity of 90% RH,
The negative electrode material is preliminarily dried by holding for 1 hour under conditions of a temperature of 130 ° C. and a nitrogen atmosphere, and then the negative electrode material after the preliminary drying is held at 200 ° C. for 30 minutes to remove moisture generated by Karl Fischer. When measured by coulometric titration,
Provided is a negative electrode material for a lithium ion battery, wherein the amount of water generated from the negative electrode material after the preliminary drying is 0.20% by mass or less with respect to 100% by mass of the negative electrode material after the preliminary drying. .

Furthermore, according to the present invention,
A negative electrode active material comprising the negative electrode material according to the first invention or the second invention of the present invention is provided.

Furthermore, according to the present invention,
There is provided a negative electrode for a lithium ion battery comprising the negative electrode active material.

Furthermore, according to the present invention,
There is provided a lithium ion battery comprising at least the negative electrode for a lithium ion battery, an electrolyte, and a positive electrode.

  According to the present invention, for example, a negative electrode material for a lithium ion battery having excellent storage characteristics can be provided.

It is a schematic diagram which shows an example of the lithium ion battery which concerns on this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the figure is a schematic diagram and does not necessarily match the actual dimensional ratio.

[First invention]
Hereinafter, an embodiment according to the first invention will be described.

<Negative electrode material>
The negative electrode material according to the present embodiment is a negative electrode material for a lithium ion battery, and an average layer spacing d ₀₀₂ (hereinafter referred to as “d ₀₀₂ ”) of (002) planes obtained by an X-ray diffraction method using CuKα rays as a radiation source. Is also 0.340 nm or more, preferably 0.350 nm or more, and more preferably 0.365 nm or more. When d ₀₀₂ is equal to or greater than the lower limit, the crystal structure is prevented from being destroyed by repeated lithium doping and dedoping, so that the charge / discharge cycle characteristics of the negative electrode material can be improved.
The upper limit of the average layer surface distance d ₀₀₂ is not particularly limited, but is usually 0.400 nm or less, preferably 0.395 nm or less, and more preferably 0.390 nm or less. When d ₀₀₂ is less than or equal to the above upper limit, the irreversible capacity of the negative electrode material can be suppressed.

  Further, in the negative electrode material according to the present embodiment, the chemical adsorption water ratio A calculated by the following procedure is 0.5% or less, preferably 0.4% or less, more preferably 0.3% or less. Has been identified to be.

(Chemical adsorption water rate A calculation procedure)
(Procedure 1) The negative electrode material according to this embodiment is held for 120 hours under conditions of a temperature of 40 ° C. and a relative humidity of 90% RH.
(Procedure 2) Using a thermogravimetric measuring device, (A) a step of holding the negative electrode material at a temperature of 130 ° C. under a nitrogen atmosphere for 1 hour, (B) the negative electrode material after the step (A) Under a nitrogen atmosphere, the temperature is raised from 40 ° C. to 540 ° C. at a rate of 10 ° C./min, and the step of measuring the weight loss of the negative electrode material is sequentially performed, and the chemical adsorption water ratio A is calculated from the following formula.
Chemical adsorption water ratio A [%] = 100 × (Y ₁ −Y ₂ ) / X
Here, X represents the weight of the negative electrode material after the step (A). Y ₁ represents the weight of the negative electrode material at 150 ° C. in the step (B). Y ₂ represents the weight of the negative electrode material at 250 ° C. in the step (B).

When the chemical adsorption water ratio A is not more than the above upper limit value, even if a negative electrode material having an average layer spacing of (002) planes larger than that of the graphite material is stored in the air for a long time, the negative electrode material is deteriorated. Can be suppressed.
Although the minimum of the said chemical adsorption water rate A is not specifically limited, Usually, it is 0.01% or more.

(Chemical adsorption water ratio A)
The reason why a negative electrode material having excellent storage characteristics is obtained when the chemical adsorption water ratio A is not more than the above upper limit value is not necessarily clear, but a negative electrode material having a lower chemical adsorption water ratio A is less likely to cause moisture adsorption. This is thought to be due to the structure.

In general, since a negative electrode material having a larger d ₀₀₂ than a graphite material has fine pores developed more than the graphite material, moisture is easily adsorbed inside the pores. When moisture is adsorbed, an irreversible reaction occurs between lithium doped in the negative electrode material and moisture, resulting in an increase in irreversible capacity during initial charging and a decrease in charge / discharge cycle characteristics. End up. For these reasons, it has been considered that a negative electrode material having a large d ₀₀₂ is inferior in storage characteristics to a graphite material (see, for example, Patent Document 2). Therefore, conventionally, attempts have been made to improve storage characteristics by closing the pores of the negative electrode material and reducing the equilibrium moisture adsorption amount (see, for example, Patent Document 2).
However, when the present inventors regenerated the negative electrode material by heating and drying the deteriorated negative electrode material to remove the moisture adsorbed in the fine pores, the negative electrode material was completely regenerated. I couldn't. Further, as in Patent Document 2, when the pores of the negative electrode material are closed, there is a problem that the charge / discharge capacity decreases.

Therefore, the present inventors have further studied diligently. As a result, the water adsorbed on the negative electrode material can be broadly divided into physical adsorbed water and chemically adsorbed water. The negative electrode material with less adsorbed amount of chemically adsorbed water has better storage characteristics and charge / discharge capacity. Became clear. That is, the inventors have found that the scale of the amount of chemically adsorbed water adsorbed is effective as a design guideline for realizing a negative electrode material having excellent storage characteristics and charge / discharge capacity, and the present invention has been achieved.
Here, the physically adsorbed water refers to adsorbed water physically present mainly as water molecules on the surface of the negative electrode material. On the other hand, chemically adsorbed water refers to adsorbed water that is present in a coordinated or chemically bonded state with the first layer on the surface of the negative electrode material.
A negative electrode material with a small amount of chemically adsorbed water has a structure in which the surface is difficult to coordinate or chemically bind moisture, or to a structure that does not easily change to such a structure when left in the atmosphere. It is thought that it has become. Therefore, the negative electrode material of the present invention having the above-mentioned chemical adsorption water ratio A equal to or less than the above upper limit is less likely to cause moisture adsorption or change in surface structure even when stored for a long time in the atmosphere. It is considered excellent.

  In the present embodiment, moisture desorbed from the negative electrode material in the step (A) is referred to as physical adsorption water, and moisture desorbed from the negative electrode material in the step (B) is referred to as chemically adsorbed water. The chemical adsorption water rate A is a water absorption rate of chemically adsorbed water desorbed between 150 ° C. and 250 ° C., and means an index of the amount of chemically adsorbed water adsorbed in the negative electrode material.

(Chemical adsorption water ratio B)
In the negative electrode material according to the present embodiment, the chemical adsorption water ratio B calculated by the following procedure is preferably 1.0% or less, more preferably 0.7% or less, and further preferably 0.5%. It is as follows.

(Calculation procedure of chemical adsorption water ratio B)
(Procedure 1) The negative electrode material according to this embodiment is held for 120 hours under conditions of a temperature of 40 ° C. and a relative humidity of 90% RH.
(Procedure 2) Using a thermogravimetric measuring device, (A) a step of holding the negative electrode material at a temperature of 130 ° C. under a nitrogen atmosphere for 1 hour, (B) the negative electrode material after the step (A) Under a nitrogen atmosphere, the temperature is increased from 40 ° C. to 540 ° C. at a rate of 10 ° C./min, and the step of measuring the weight loss of the negative electrode material is sequentially performed, and the chemical adsorption water ratio B is calculated from the following formula.
Chemical adsorption water ratio B [%] = 100 × (Y ₂ −Y ₃ ) / X
Here, X represents the weight of the negative electrode material after the step (A). Y ₂ represents the weight of the negative electrode material at 250 ° C. in the step (B). Y ₃ represents the weight of the negative electrode material at 500 ° C. in the step (B).

  When the chemical adsorption water ratio B is not more than the above upper limit value, the storage characteristics of the negative electrode material can be further improved. Furthermore, the charge / discharge capacity of the negative electrode material can be further improved when the chemical adsorption water ratio B is not more than the upper limit. The chemical adsorption water rate B is the water absorption rate of chemically adsorbed water desorbed between 250 ° C. and 500 ° C., and the chemical adsorption is less likely to desorb than the chemically adsorbed water determined at the above-mentioned chemical adsorbed water rate A. It means an index of water adsorption.

In the negative electrode material according to the present embodiment, the weight reduction rate at 250 ° C. defined by the following formula is preferably 0.6% or less, and more preferably 0.5% or less.
Weight reduction rate at 250 ° C. [%] = 100 × (XY ₂ ) / X
Here, X represents the weight of the negative electrode material after the step (A). Y ₂ represents the weight of the negative electrode material at 250 ° C. in the step (B).
When the weight reduction rate is not more than the upper limit, the storage characteristics of the negative electrode material can be further improved.

In the negative electrode material according to the present embodiment, the weight reduction rate at 500 ° C. defined by the following formula is preferably 1.6% or less, more preferably 1.2% or less.
Weight reduction rate at 500 ° C. [%] = 100 × (XY ₃ ) / X
Here, X represents the weight of the negative electrode material after the step (A). Y ₃ represents the weight of the negative electrode material at 500 ° C. in the step (B).
When the weight reduction rate is not more than the upper limit, the storage characteristics of the negative electrode material can be further improved.

(Water content by Karl Fischer coulometric titration)
In the negative electrode material according to this embodiment, the negative electrode material is held for 120 hours under the conditions of a temperature of 40 ° C. and a relative humidity of 90% RH, and then the negative electrode material is held for 1 hour under the condition of a temperature of 130 ° C. and a nitrogen atmosphere. The moisture generated from the negative electrode material after the preliminary drying was measured by the Karl Fischer coulometric titration method. The amount is preferably 0.20% by mass or less, more preferably 0.15% by mass or less, particularly preferably 0.10% by mass or less, with respect to 100% by mass of the negative electrode material after the preliminary drying. is there.
The storage characteristic of a negative electrode material can be further improved as the said moisture content is below the said upper limit. The water content is an index of the amount of chemically adsorbed water that is desorbed by being held at 200 ° C. for 30 minutes.

(Crystallite size)
The negative electrode material according to the present embodiment preferably has a crystallite size in the c-axis direction obtained by X-ray diffraction (hereinafter sometimes abbreviated as “Lc ₍₀₀₂₎ ”) of 5 nm or less. More preferably, it is 3 nm or less, More preferably, it is 2 nm or less.

(Average particle size)
The negative electrode material according to this embodiment preferably has a 50% cumulative particle size (D ₅₀ , average particle size) in a volume-based cumulative distribution of 1 μm to 50 μm, and more preferably 2 μm to 30 μm. preferable. Thereby, a high-density negative electrode can be produced.

(Specific surface area)
In the negative electrode material of the present embodiment, the specific surface area according to the BET three-point method in nitrogen adsorption is preferably 1 m ² / g or more and 15 m ² / g or less, and more preferably 3 m ² / g or more and 8 m ² / g or less. .
When the specific surface area by the BET three-point method in nitrogen adsorption is not more than the above upper limit value, the irreversible reaction between the negative electrode material and the electrolytic solution can be further suppressed.
Moreover, appropriate permeability to the negative electrode material of electrolyte solution can be obtained because the specific surface area by the BET three point method in nitrogen adsorption is more than the said lower limit.

The calculation method of the specific surface area is as follows.
The monomolecular adsorption amount W _m is calculated from the following formula (1), the total surface area S _total is calculated from the following formula (2), and the specific surface area S is obtained from the following formula (3).
1 / [W · {(P _o / P) −1}] = {(C−1) / (W _m · C)} (P / P _o ) (1 / (W _m · C) (1)

In the above formula (1), P: pressure of an adsorbate gas in adsorption equilibrium, P _o : saturated vapor pressure of the adsorbate at the adsorption temperature, W: adsorption amount at the adsorption equilibrium pressure P, W _m : monolayer adsorption Amount, C: constant related to the magnitude of the interaction between the solid surface and the adsorbate (C = exp {(E ₁ -E ₂ ) RT}) [E ₁ : heat of adsorption of the first layer (kJ / mol), E ₂ : Heat of liquefaction at measurement temperature of adsorbate (kJ / mol)]

S _total = (W _m NA _cs ) M (2)
In the above formula (2), N: Avogadro number, M: molecular weight, A _cs : adsorption cross section

S = S _total / w (3)
In formula (3), w: sample weight (g)

(Carbon dioxide adsorption amount)
In the negative electrode material according to this embodiment, the amount of carbon dioxide adsorbed is preferably less than 10 ml / g, more preferably 8 ml / g or less, and further preferably 6 ml / g or less. When the adsorption amount of carbon dioxide gas is not more than the above upper limit value, the storage characteristics of the negative electrode material can be further improved.
In addition, the negative electrode material according to the present embodiment preferably has an adsorption amount of carbon dioxide gas of 0.05 ml / g or more, and more preferably 0.1 ml / g or more. When the adsorption amount of carbon dioxide gas is equal to or more than the lower limit, the charge capacity of lithium can be further improved.
The amount of carbon dioxide adsorbed is measured by using an ASAP-2000M manufactured by Micromeritics Instrument Corporation, which is obtained by vacuum drying a negative electrode material at 130 ° C. for 3 hours or more using a vacuum dryer. It can be carried out.

(Halogen content)
The negative electrode material according to this embodiment preferably has a halogen content of less than 50 ppm, more preferably 30 ppm or less, and even more preferably 10 ppm or less. When the halogen content is not more than the above upper limit, the storage characteristics of the negative electrode material can be further improved. The halogen content can be controlled by adjusting the halogen gas concentration in the processing gas used for the carbonization treatment and the halogen amount contained in the raw material of the negative electrode material. The halogen content is calculated by burning the negative electrode material, absorbing the halogen hydrogen gas in the generated combustion gas into sodium hydroxide, and then quantifying the halogen content in this solution with an ion chromatography analyzer. it can.

(Discharge capacity)
The negative electrode material of the present embodiment has a discharge capacity of 360 mAh / g or more, more preferably 380 mAh / g or more, when charging / discharging under the charge / discharge conditions described later for a half cell manufactured under the conditions described later. More preferably, it is 400 mAh / g or more, and particularly preferably 420 mAh / g or more. The upper limit of the discharge capacity is not particularly limited and is preferably as many as possible. However, in reality, it is 700 mAh / g or less, and usually 500 mAh / g or less. In the present specification, “mAh / g” indicates a capacity per 1 g of the negative electrode material.

(Half cell manufacturing conditions)
The conditions for producing the above-described half cell will be described.
The negative electrode used is formed of the negative electrode material. More specifically, an electrode is formed using a composition in which a negative electrode material, carboxymethyl cellulose, styrene-butadiene rubber, and acetylene black are mixed at a weight ratio of 100: 1.5: 3.0: 2.0. The formed one is used.
The counter electrode uses metallic lithium.
As the electrolytic solution, a solution obtained by dissolving LiPF ₆ in a carbonate solvent (a mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1: 1) at a ratio of 1 M is used.

The negative electrode can be produced, for example, as follows.
First, a predetermined amount of negative electrode material, carboxymethylcellulose, styrene-butadiene rubber, acetylene black, and water are mixed with stirring to prepare a slurry. The obtained slurry is applied onto a copper foil as a current collector, preliminarily dried at 60 ° C. for 2 hours, and then vacuum dried at 120 ° C. for 15 hours. Subsequently, the negative electrode comprised with the negative electrode material can be obtained by cutting out to a predetermined magnitude | size.

In addition, the negative electrode has a disk shape with a diameter of 13 mm, the negative electrode active material layer (a portion obtained by removing the current collector from the negative electrode) has a disk shape with a thickness of 50 μm, and the counter electrode (an electrode made of metallic lithium) It can be a disk with a diameter of 12 mm and a thickness of 1 mm.
Further, the shape of the half cell can be a 2032 type coin cell shape.

(Charge / discharge conditions)
The charging / discharging conditions of the half cell described above are as follows.
Measurement temperature: 25 ° C
Charging method: constant current constant voltage method, charging current: 25 mA / g, charging voltage: 0 mV, charging end current: 2.5 mA / g
Discharge method: constant current method, discharge current: 25 mA / g, final discharge voltage: 2.5 V

  Note that “charging” for a half cell refers to moving lithium ions from an electrode made of metallic lithium to an electrode made of a negative electrode material by applying a voltage. “Discharge” refers to a phenomenon in which lithium ions move from an electrode made of a negative electrode material to an electrode made of metallic lithium.

<Method for producing negative electrode material>
Next, the manufacturing method of the negative electrode material according to the present embodiment will be described.
The negative electrode material according to the present embodiment can be produced, for example, by carbonizing a specific resin composition as a raw material under appropriate conditions.
The production of the anode material using the resin composition as a raw material itself has been performed in the prior art. However, in the present embodiment, factors such as (1) the composition of the resin composition, (2) the conditions for the carbonization treatment, and (3) the ratio of the raw material to the space where the carbonization treatment is performed are highly controlled. In order to obtain the negative electrode material according to the present embodiment, it is important to highly control these factors.
In particular, the present inventors set the conditions (1) and (2) appropriately in order to obtain a negative electrode material having the chemical adsorption water ratio A equal to or lower than the upper limit value. It was found that it is important to set the occupation ratio of the raw material with respect to the space to be carbonized lower than the conventional standard.
Hereinafter, an example of the manufacturing method of the negative electrode material which concerns on this embodiment is shown. However, the manufacturing method of the negative electrode material according to the present embodiment is not limited to the following example.

(Resin composition)
First, (1) a resin composition to be carbonized is selected as a raw material for the negative electrode material.
Examples of the resin contained in the resin composition that is the raw material of the negative electrode material according to the present embodiment include a thermosetting resin; a thermoplastic resin; a petroleum-based tar and pitch that are by-produced during ethylene production, and a coal produced by dry distillation. Coal tar, heavy components or pitch obtained by distilling off low boiling components of coal tar, petroleum-based or coal-based tar or pitch such as tar or pitch obtained by coal liquefaction; And the like subjected to crosslinking treatment. Among these, one kind or a combination of two or more kinds can be used. Among these, a thermosetting resin is preferable because it can be purified at the raw material stage, a negative electrode material with few impurities can be obtained, and the steps required for purification can be greatly shortened, leading to cost reduction.

Examples of the thermosetting resin include: phenol resins such as novolak type phenol resins and resol type phenol resins; epoxy resins such as bisphenol type epoxy resins and novolac type epoxy resins; melamine resins; urea resins; aniline resins; Examples include furan resins; ketone resins; unsaturated polyester resins; urethane resins. In addition, modified products obtained by modifying these with various components can also be used.
Among these, phenol resins such as novolac type phenol resin and resol type phenol resin; melamine resin; urea resin; aniline resin, which are resins using formaldehyde, are preferable because of the high residual carbon ratio.

Moreover, when using a thermosetting resin, the hardening | curing agent can be used together.
As the curing agent used, for example, hexamethylenetetramine, resol type phenol resin, polyacetal, paraformaldehyde and the like can be used in the case of a novolak type phenol resin. In the case of a resol type phenol resin, melamine resin, urea resin, aniline resin, hexamethylenetetramine or the like can be used.
The compounding quantity of a hardening | curing agent is 0.1 to 50 mass parts normally with respect to 100 mass parts of said thermosetting resins.

  Moreover, in the resin composition as a raw material of negative electrode material, an additive can be mix | blended other than the said thermosetting resin and a hardening | curing agent.

  Although it does not specifically limit as an additive used here, For example, the carbon material precursor carbonized at 200 to 800 degreeC, an organic acid, an inorganic acid, a nitrogen-containing compound, an oxygen-containing compound, an aromatic compound, nonferrous A metal element etc. can be mentioned. These additives can be used alone or in combination of two or more depending on the type and properties of the resin used.

  The method for preparing the resin composition is not particularly limited. For example, (1) a method in which the above resin and other components are melt-mixed, (2) the above resin and other components are dissolved in a solvent. (3) The resin and other components may be pulverized and mixed.

  The apparatus for preparing the resin composition is not particularly limited. For example, when melt mixing is performed, a kneading apparatus such as a kneading roll, a single screw or a twin screw kneader can be used. When performing dissolution and mixing, a mixing device such as a Henschel mixer or a disperser can be used. When performing pulverization and mixing, for example, an apparatus such as a hammer mill or a jet mill can be used.

  The resin composition thus obtained may be one obtained by physically mixing a plurality of types of components, or is applied during mixing (stirring, kneading, etc.) during preparation of the resin composition. A part of the material may be chemically reacted with mechanical energy and thermal energy converted from the mechanical energy. Specifically, a mechanochemical reaction using mechanical energy or a chemical reaction using thermal energy may be performed.

(Carbonization treatment)
Next, the obtained resin composition is carbonized.
Here, as the conditions for the carbonization treatment, for example, the temperature is raised from normal temperature to 1 ° C./hour to 200 ° C./hour, 800 ° C. to 3000 ° C., 0.01 Pa to 101 kPa (1 atm), The reaction can be performed for 1 hour to 50 hours, preferably 0.5 hours to 10 hours. The atmosphere during carbonization is preferably an inert atmosphere such as nitrogen or helium gas; a substantially inert atmosphere in which a trace amount of oxygen is present in the inert gas; a reducing gas atmosphere, or the like. . By doing in this way, thermal decomposition (oxidative decomposition) of resin can be suppressed and a desired negative electrode material can be obtained.

  Conditions such as temperature and time during the carbonization treatment can be appropriately adjusted in order to optimize the characteristics of the negative electrode material.

In addition, you may perform a pre carbonization process before performing the said carbonization process.
Here, the conditions for the pre-carbonization treatment are not particularly limited. Thus, even if the resin composition is infusibilized by performing pre-carbonization treatment before carbonization treatment and pulverization treatment of the resin composition or the like is performed before the carbonization treatment step, the resin composition after pulverization can be obtained. It is possible to prevent re-fusion during carbonization and to obtain a desired negative electrode material efficiently.

Moreover, you may perform the hardening process of a resin composition before this pre carbonization process.
Although it does not specifically limit as a hardening processing method, For example, it can carry out by the method of giving heat quantity which can perform hardening reaction to a resin composition, the method of thermosetting, or the method of using together a thermosetting resin and a hardening | curing agent. . As a result, the pre-carbonization treatment can be performed substantially in the solid phase, so that the carbonization treatment or the pre-carbonization treatment can be performed while maintaining the structure of the thermosetting resin to some extent, and the structure and characteristics of the negative electrode material are controlled. Will be able to.

  In addition, when performing the carbonization treatment or the pre-carbonization treatment, a metal, a pigment, a lubricant, an antistatic agent, an antioxidant, or the like is added to the resin composition to impart desired characteristics to the negative electrode material. You can also.

  When the said hardening process or pre carbonization process is performed, you may grind | pulverize a processed material before the said carbonization process after that. In such a case, variation in the thermal history during carbonization can be reduced, and the uniformity of the surface state of the obtained negative electrode material can be increased. And the handleability of a processed material can be improved.

(Occupation ratio of raw materials in the space for carbonization)
Moreover, in order to obtain the negative electrode material according to the present embodiment, it is important to appropriately adjust the occupation ratio of the raw material in the space where the carbonization treatment is performed. Specifically, the occupation ratio of the raw material with respect to the space for carbonization is preferably set to 10.0 kg / m ³ or less, more preferably 5.0 kg / m ³ or less, and particularly preferably 1.0 kg / m ³ or less. . Here, the space for performing the carbonization treatment usually represents the furnace volume of the heat treatment furnace used for the carbonization treatment.
The reason why the negative electrode material according to the present embodiment can be obtained by setting the occupation ratio of the raw material in the space for performing the carbonization treatment to be equal to or less than the above upper limit value is not necessarily clear, but from the raw material (resin composition) during the carbonization treatment. This is probably because the generated gas is efficiently removed out of the system, so that the surface of the obtained negative electrode material tends to have a structure in which moisture is not easily coordinated or chemically bonded.

  The negative electrode material according to this embodiment can be obtained by the above procedure.

<Negative electrode active material>
Hereinafter, the negative electrode active material according to the present embodiment will be described.
The negative electrode active material refers to a material capable of taking in and out lithium ions in a lithium ion secondary battery. The negative electrode active material according to the present embodiment includes the negative electrode material according to the present embodiment described above.

  The negative electrode active material according to the present embodiment may further include a type of negative electrode material different from the negative electrode material described above. Examples of such a negative electrode material include generally known negative electrode materials such as silicon, silicon monoxide, and graphite materials.

  Among these, the negative electrode active material according to the present embodiment preferably includes a graphite material in addition to the negative electrode material according to the present embodiment described above. Thereby, the charge / discharge capacity of the obtained lithium ion battery can be improved. Therefore, the obtained lithium ion battery can be made particularly excellent in the balance between charge / discharge capacity and charge / discharge efficiency.

  The particle size (average particle size) at the time of 50% accumulation in the volume-based cumulative distribution of the graphite material used is preferably 2 μm or more and 50 μm or less, and more preferably 5 μm or more and 30 μm or less. Thereby, a high-density negative electrode can be produced while maintaining high charge / discharge efficiency.

<Anode for lithium ion battery, lithium ion battery>
Hereinafter, the negative electrode for lithium ion batteries and the lithium ion battery according to this embodiment will be described.

The negative electrode for a lithium ion battery according to the present embodiment (hereinafter sometimes simply referred to as a negative electrode) is produced using the negative electrode active material according to the present embodiment described above. Thereby, the negative electrode excellent in storage characteristics and charge / discharge capacity can be provided.
In addition, the lithium ion battery according to the present embodiment is manufactured using the negative electrode according to the present embodiment. Thereby, a lithium ion battery excellent in storage characteristics and charge / discharge capacity can be provided.

Hereinafter, preferred embodiments of a negative electrode for a lithium ion battery and a lithium ion battery according to the present embodiment will be described.
FIG. 1 is a schematic view showing an example of a lithium ion battery according to this embodiment.

  As shown in FIG. 1, the lithium ion battery 10 includes a negative electrode 13, a positive electrode 21, an electrolytic solution 16, and a separator 18.

As shown in FIG. 1, the negative electrode 13 includes a negative electrode active material layer 12 and a negative electrode current collector 14.
The negative electrode current collector 14 is not particularly limited, and generally known negative electrode current collectors can be used. For example, copper foil or nickel foil can be used.

The negative electrode active material layer 12 is composed of the negative electrode active material according to the present embodiment described above.
The negative electrode 13 can be manufactured as follows, for example.

For 100 parts by weight of the negative electrode active material, generally known organic polymer binders (for example, fluorine-based polymers such as polyvinylidene fluoride and polytetrafluoroethylene; styrene / butadiene rubber, butyl rubber, butadiene rubber, etc.) 1 to 30 parts by weight and an appropriate amount of a viscosity adjusting solvent (N-methyl-2-pyrrolidone, dimethylformamide, etc.) or water is added and kneaded to prepare a negative electrode slurry. Prepare.
The negative electrode active material layer 12 can be obtained by molding the obtained slurry into a sheet shape, a pellet shape, or the like by compression molding, roll molding, or the like. And the negative electrode 13 can be obtained by laminating | stacking the negative electrode active material layer 12 and the negative electrode collector 14 which were obtained in this way.
Moreover, the negative electrode 13 can also be manufactured by apply | coating the obtained negative electrode slurry to the negative electrode collector 14, and drying.

  The electrolyte solution 16 fills the space between the positive electrode 21 and the negative electrode 13 and is a layer in which lithium ions move by charge / discharge.

  The electrolytic solution 16 is not particularly limited, and a generally known electrolytic solution can be used. For example, a solution obtained by dissolving a lithium salt serving as an electrolyte in a non-aqueous solvent is used.

  Examples of the non-aqueous solvent include cyclic esters such as propylene carbonate, ethylene carbonate, and γ-butyrolactone; chain esters such as dimethyl carbonate and diethyl carbonate; chain ethers such as dimethoxyethane; or a mixture thereof. Can be used.

Is not particularly limited as electrolytes generally be a known electrolyte, for example, it may be used lithium metal salt such as LiClO _4, LiPF _6. Further, the above salts can be mixed with polyethylene oxide, polyacrylonitrile, etc. and used as a solid electrolyte.

  It does not specifically limit as the separator 18, Generally a well-known separator can be used, For example, porous films, nonwoven fabrics, etc., such as polyethylene and a polypropylene, can be used.

As illustrated in FIG. 1, the positive electrode 21 includes a positive electrode active material layer 20 and a positive electrode current collector 22.
It does not specifically limit as the positive electrode active material layer 20, Generally, it can form with a well-known positive electrode active material. Is not particularly limited as the cathode active material include lithium cobalt oxide (LiCoO _2), lithium nickel oxide (LiNiO _2), composite oxides such as lithium manganese oxide (LiMn ₂ O _4); polyaniline, polypyrrole, etc. Or the like can be used.

The positive electrode current collector 22 is not particularly limited, and generally known positive electrode current collectors can be used. For example, an aluminum foil can be used.
And the positive electrode 21 in this embodiment can be manufactured with the manufacturing method of a well-known positive electrode generally.

[Second invention]
Hereinafter, an embodiment according to the second invention will be described.
<Negative electrode material>
The negative electrode material according to the present embodiment is a negative electrode material for a lithium ion battery, and an average layer spacing d ₀₀₂ (hereinafter referred to as “d ₀₀₂ ”) of (002) planes obtained by an X-ray diffraction method using CuKα rays as a radiation source. Is also 0.340 nm or more, preferably 0.350 nm or more, and more preferably 0.365 nm or more. When d ₀₀₂ is equal to or greater than the lower limit, the crystal structure is prevented from being destroyed by repeated lithium doping and dedoping, so that the charge / discharge cycle characteristics of the negative electrode material can be improved.
The upper limit of the average layer surface distance d ₀₀₂ is not particularly limited, but is usually 0.400 nm or less, preferably 0.395 nm or less, and more preferably 0.390 nm or less. When d ₀₀₂ is less than or equal to the above upper limit, the irreversible capacity of the negative electrode material can be suppressed.

In addition, the negative electrode material according to the present embodiment is held for 120 hours under the conditions of a temperature of 40 ° C. and a relative humidity of 90% RH, and then the negative electrode material is maintained at a temperature of 130 ° C. under a nitrogen atmosphere for 1 hour. Holding and pre-drying, and then measuring the moisture generated by holding the negative electrode material after the pre-drying at 200 ° C. for 30 minutes by Karl Fischer coulometric titration, the above after the pre-drying The amount of water generated from the negative electrode material is 0.20% by mass or less, preferably 0.15% by mass or less, more preferably 0.10% with respect to 100% by mass of the negative electrode material after the preliminary drying. It is below mass%.
The storage characteristic of a negative electrode material can be improved as the said moisture content is below the said upper limit. The water content is an index of the amount of chemically adsorbed water that is desorbed by being held at 200 ° C. for 30 minutes.

(Crystallite size)
The negative electrode material according to the present embodiment preferably has a crystallite size in the c-axis direction obtained by X-ray diffraction (hereinafter sometimes abbreviated as “Lc ₍₀₀₂₎ ”) of 5 nm or less. More preferably, it is 3 nm or less, More preferably, it is 2 nm or less.

(Average particle size)
The negative electrode material according to this embodiment preferably has a 50% cumulative particle size (D ₅₀ , average particle size) in a volume-based cumulative distribution of 1 μm to 50 μm, and more preferably 2 μm to 30 μm. preferable. Thereby, a high-density negative electrode can be produced.

(Specific surface area)
In the negative electrode material of the present embodiment, the specific surface area according to the BET three-point method in nitrogen adsorption is preferably 1 m ² / g or more and 15 m ² / g or less, and more preferably 3 m ² / g or more and 8 m ² / g or less. .
When the specific surface area by the BET three-point method in nitrogen adsorption is not more than the above upper limit value, the irreversible reaction between the negative electrode material and the electrolytic solution can be further suppressed.
Moreover, appropriate permeability to the negative electrode material of electrolyte solution can be obtained because the specific surface area by the BET three point method in nitrogen adsorption is more than the said lower limit.

  Since the calculation method of the specific surface area is the same as that of the negative electrode material according to the first invention described above, description thereof is omitted.

(Carbon dioxide adsorption amount)
In the negative electrode material according to this embodiment, the amount of carbon dioxide adsorbed is preferably less than 10 ml / g, more preferably 8 ml / g or less, and further preferably 6 ml / g or less. When the adsorption amount of carbon dioxide gas is not more than the above upper limit value, the storage characteristics of the negative electrode material can be further improved.
In addition, the negative electrode material according to the present embodiment preferably has an adsorption amount of carbon dioxide gas of 0.05 ml / g or more, and more preferably 0.1 ml / g or more. When the adsorption amount of carbon dioxide gas is equal to or more than the lower limit, the charge capacity of lithium can be further improved.
The amount of carbon dioxide adsorbed is measured by using an ASAP-2000M manufactured by Micromeritics Instrument Corporation, which is obtained by vacuum drying a negative electrode material at 130 ° C. for 3 hours or more using a vacuum dryer. It can be carried out.

(Halogen content)
The negative electrode material according to this embodiment preferably has a halogen content of less than 50 ppm, more preferably 30 ppm or less, and even more preferably 10 ppm or less. When the halogen content is not more than the above upper limit, the storage characteristics of the negative electrode material can be further improved. The halogen content can be controlled by adjusting the halogen gas concentration in the processing gas used for the carbonization treatment and the halogen amount contained in the raw material of the negative electrode material. The halogen content is calculated by burning the negative electrode material, absorbing the halogen hydrogen gas in the generated combustion gas into sodium hydroxide, and then quantifying the halogen content in this solution with an ion chromatography analyzer. it can.

(Discharge capacity)
In the negative electrode material of the present embodiment, the discharge capacity when charging / discharging under the charge / discharge conditions described in the first invention is preferably 360 mAh / g or more for the half cell produced under the conditions described in the first invention. More preferably, it is 380 mAh / g or more, More preferably, it is 400 mAh / g or more, Most preferably, it is 420 mAh / g or more. The upper limit of the discharge capacity is not particularly limited and is preferably as many as possible. However, in reality, it is 700 mAh / g or less, and usually 500 mAh / g or less. In the present specification, “mAh / g” indicates a capacity per 1 g of the negative electrode material.

<Method for producing negative electrode material>
The negative electrode material which concerns on 2nd invention can be manufactured according to the manufacturing method of the negative electrode material which concerns on 1st invention. Details are omitted here.

<Negative electrode active material>
Hereinafter, the negative electrode active material according to the present embodiment will be described.
The negative electrode active material refers to a material capable of taking in and out lithium ions in a lithium ion secondary battery. The negative electrode active material according to the present embodiment includes the negative electrode material according to the present embodiment described above.

  The negative electrode active material according to the present embodiment may further include a type of negative electrode material different from the negative electrode material described above. Examples of such a negative electrode material include generally known negative electrode materials such as silicon, silicon monoxide, and graphite materials.

  Among these, the negative electrode active material according to the present embodiment preferably includes a graphite material in addition to the negative electrode material according to the present embodiment described above. Thereby, the charge / discharge capacity of the obtained lithium ion battery can be improved. Therefore, the obtained lithium ion battery can be made particularly excellent in the balance between charge / discharge capacity and charge / discharge efficiency.

  The particle size (average particle size) at the time of 50% accumulation in the volume-based cumulative distribution of the graphite material used is preferably 2 μm or more and 50 μm or less, and more preferably 5 μm or more and 30 μm or less. Thereby, a high-density negative electrode can be produced while maintaining high charge / discharge efficiency.

<Anode for lithium ion battery, lithium ion battery>
The negative electrode for lithium ion batteries and the lithium ion battery according to the second invention can be produced according to the negative electrode for lithium ion batteries and the lithium ion battery according to the first invention. Details are omitted here.

  As mentioned above, although embodiment of each invention of this invention was described, these are illustrations of this invention and can employ | adopt various structures other than the above.

  Needless to say, the present inventions described above can be combined within a range in which the contents do not conflict with each other.

  Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to these. In the examples, “part” means “part by weight”.

[1] Evaluation method of negative electrode material First, the evaluation method of the negative electrode material obtained by the Example and comparative example which are mentioned later is demonstrated.

1. Particle size distribution The particle size distribution of the negative electrode material was measured by a laser diffraction method using a laser diffraction particle size distribution measuring apparatus LA-920 manufactured by Horiba. From the measurement results, the particle size (D ₅₀ , average particle size) at 50% accumulation in the volume-based cumulative distribution was determined for the negative electrode material.

2. Specific surface area It measured by the BET 3 point | piece method in nitrogen adsorption | suction using the Nova-1200 apparatus made from Yuasa. The specific calculation method is as described above.

3. Negative electrode material d ₀₀₂ and Lc ₍₀₀₂₎
Using an X-ray diffractometer “XRD-7000” manufactured by Shimadzu Corporation, the average layer spacing d ₀₀₂ of the (002) plane was measured.
From the spectrum obtained from the X-ray diffraction measurement of the negative electrode material, the average layer spacing d ₀₀₂ of the (002) plane was calculated from the following Bragg equation.
λ = 2d _hkl sinθ Bragg equation (d _hkl = d ₀₀₂ )
λ: wavelength of characteristic X-ray K _α1 output from the cathode θ: reflection angle of spectrum Lc ₍₀₀₂₎ was measured as follows.
It was determined from the half width of the 002 plane peak and the diffraction angle in the spectrum obtained from the X-ray diffraction measurement using the following Scherrer equation.
Lc ₍₀₀₂₎ = 0.94 λ / (βcos θ) (Scherrer equation)
Lc ₍₀₀₂₎ : Crystallite size λ: Wavelength of characteristic X-ray K _α1 output from the cathode β: Half width of peak (radian)
θ: Spectral reflection angle

4). Carbon dioxide gas adsorption amount Carbon dioxide gas adsorption amount was measured using a vacuum drier with a negative electrode material vacuum-dried at 130 ° C. for 3 hours or more as a measurement sample, using ASAP-2000M manufactured by Micromeritics Instrument Corporation. Done using.
A measurement sample tube (0.5 g) was placed in a measurement sample tube and dried under reduced pressure at 300 ° C. for 3 hours or more under a reduced pressure of 0.2 Pa or less. Thereafter, the amount of carbon dioxide adsorbed was measured.
The adsorption temperature is 0 ° C., the pressure is reduced until the pressure of the sample tube containing the measurement sample becomes 0.6 Pa or less, carbon dioxide gas is introduced into the sample tube, and the equilibrium pressure in the sample tube is 0.11 MPa (relative pressure). The amount of carbon dioxide adsorbed until it reached (corresponding to 0.032) was determined by the constant volume method and expressed in ml / g. The adsorption amount is a value converted to a standard state (STP).

5. Content of Chlorine The negative electrode material was burned using an oxyhydrogen flame combustion apparatus, and HCl in the produced combustion gas was absorbed in 0.01 mol NaOH aqueous solution. Next, the chlorine content in the aqueous solution was quantified with an ion chromatography analyzer. The calibration curve of the ion chromatography analyzer was prepared by analyzing a solution prepared by diluting a chloride ion standard solution for ion chromatography (sodium chloride aqueous solution, chlorine ion concentration 1000 ppm, manufactured by Kanto Chemical Co., Inc.). .

6). Chemical adsorption water rate A and B
The chemical adsorption water ratios A and B were measured by the following procedures, respectively.
(Procedure 1) In an apparatus of a small environmental tester (SH-241 manufactured by ESPEC), 1 g of a negative electrode material was held for 120 hours under the conditions of a temperature of 40 ° C. and a relative humidity of 90% RH. The negative electrode material was spread in a container having a length of 5 cm, a width of 8 cm, and a height of 1.5 cm so as to be as thin as possible, and then left in the apparatus.
(Procedure 2) Using a thermogravimetry apparatus (TG / DTA6300 manufactured by Seiko Instruments), (A) a step of holding 10 mg of the negative electrode material under conditions of a temperature of 130 ° C. and a nitrogen atmosphere for 1 hour; and (B) the above (A) The above-mentioned negative electrode material after the step is heated at a rate of 10 ° C./min from a temperature of 40 ° C. to 540 ° C. in a nitrogen atmosphere, and the step of measuring the weight loss of the negative electrode material is sequentially performed. From the above, the chemical adsorption water ratio A and the chemical adsorption water ratio B were calculated.
Chemical adsorption water ratio A [%] = 100 × (Y ₁ −Y ₂ ) / X
Chemical adsorption water ratio B [%] = 100 × (Y ₂ −Y ₃ ) / X
Here, X represents the weight of the negative electrode material after the step (A). Y ₁ represents the weight of the negative electrode material at 150 ° C. in the step (B). Y ₂ represents the weight of the negative electrode material at 250 ° C. in the step (B). Y ₃ represents the weight of the negative electrode material at 500 ° C. in the step (B).

7). Measurement of water content by Karl Fischer coulometric titration The water content by Karl Fischer coulometric titration was measured by the following procedure.
(Procedure 1) In an apparatus of a small environmental tester (SH-241 manufactured by ESPEC), 1 g of a negative electrode material was held for 120 hours under the conditions of a temperature of 40 ° C. and a relative humidity of 90% RH. The negative electrode material was spread in a container having a length of 5 cm, a width of 8 cm, and a height of 1.5 cm so as to be as thin as possible, and then left in the apparatus.
(Procedure 2) The negative electrode material was preliminarily dried by holding it for 1 hour under conditions of a temperature of 130 ° C. and a nitrogen atmosphere, and then the negative electrode material after preliminarily drying using CA-06 manufactured by Mitsubishi Chemical Analytech Inc. was 200 The water generated by holding at 30 ° C. for 30 minutes was measured by the Karl Fischer coulometric titration method.

8). Storage characteristics The initial efficiency of each of the negative electrode material immediately after production and the negative electrode material after the following storage test was measured according to the following method. Next, the change rate of the initial efficiency was calculated.

(Preservation test)
1 g of the negative electrode material was held for 7 days under conditions of a temperature of 40 ° C. and a relative humidity of 90% RH in a small environmental tester (SH-241 manufactured by ESPEC). The negative electrode material was spread in a container having a length of 5 cm, a width of 8 cm, and a height of 1.5 cm so as to be as thin as possible, and then left in the apparatus. Thereafter, the negative electrode material was dried by holding at a temperature of 130 ° C. for 1 hour under a nitrogen atmosphere.

(1) Production of half cell With respect to 100 parts of the negative electrode material obtained in Examples and Comparative Examples described later, 1.5 parts of carboxymethyl cellulose (manufactured by Daicel Finechem, CMC Daicel 2200), styrene-butadiene rubber (manufactured by JSR) , TRD-2001) 3.0 parts, 2.0 parts of acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 100 parts of distilled water were added and stirred and mixed with a rotating / revolving mixer to prepare a negative electrode slurry. did.

  The prepared negative electrode slurry was applied to one side of a copper foil having a thickness of 14 μm (Furukawa Electric Co., Ltd., NC-WS), followed by preliminary drying in air at 60 ° C. for 2 hours, and then at 120 ° C. for 15 hours. Vacuum dried. After vacuum drying, the electrode was pressure-formed by a roll press. This was cut into a disk shape having a diameter of 13 mm to produce a negative electrode. The thickness of the negative electrode active material layer was 50 μm.

  Metallic lithium was formed in a disk shape with a diameter of 12 mm and a thickness of 1 mm to produce a counter electrode. In addition, a polyolefin porous film (manufactured by Celgard, trade name: Celgard 2400) was used as a separator.

Using the negative electrode, the counter electrode, and the separator described above, a mixed solvent obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 as an electrolytic solution and adding LiPF ₆ at a ratio of 1 M was used in an argon atmosphere. A 2032 type coin cell-shaped bipolar half cell was manufactured in the glove box, and the evaluation described below was performed on the half cell.

(2) Charging / discharging of a half cell Charging / discharging was performed on the following conditions.
Measurement temperature: 25 ° C
Charging method: constant current constant voltage method, charging current: 25 mA / g, charging voltage: 0 mV, charging end current: 2.5 mA / g
Discharge method: constant current method, discharge current: 25 mA / g, final discharge voltage: 2.5 V

Further, the charge capacity and discharge capacity [mAh / g] per gram of the negative electrode material were determined based on the charge capacity and discharge capacity values obtained under the above conditions. Further, the initial efficiency and the rate of change of the initial efficiency were obtained from the following formula.
Initial efficiency [%] = 100 x (Discharge capacity) / (Charge capacity)
Rate of change in initial efficiency [%] = 100 x (initial efficiency after storage test) / (initial efficiency immediately after production)

[2] Production of negative electrode material (Example 1)
An oxidized pitch was prepared according to the method described in paragraph 0051 of JP-A-8-279358. Next, using this oxidized pitch as a raw material, the following steps (a) to (f) were carried out in order, whereby a negative electrode material 1 was obtained.

(A) In a heat treatment furnace having a furnace internal volume of 60 L (length 50 cm, width 40 cm, height 30 cm), 510 g of oxidation pitch was spread and allowed to stand as thin as possible. Thereafter, the temperature was raised from room temperature to 500 ° C. at 100 ° C./hour without any of reducing gas replacement, inert gas replacement, reducing gas flow, and inert gas flow.

(B) Next, degreasing treatment was performed at 500 ° C. for 2 hours without cooling gas replacement, inert gas replacement, reducing gas flow, and inert gas flow, and then cooled.

(C) The obtained powder was finely pulverized with a vibration ball mill.
(D) Thereafter, 204 g of the obtained powder was spread and allowed to stand as thin as possible in a heat treatment furnace having a furnace volume of 24 L (length 40 cm, width 30 cm, height 20 cm). Subsequently, the temperature was raised from room temperature to 1200 ° C. at 100 ° C./hour under inert gas (nitrogen) substitution and circulation.

(E) Under an inert gas (nitrogen) flow, it was kept at 1200 ° C. for 8 hours and carbonized.
(F) Under natural gas (nitrogen) circulation, the mixture was naturally cooled to 600 ° C., and then cooled from 600 ° C. to 100 ° C. at 100 ° C./hour.

In addition, the occupation ratio of the raw material with respect to the space which carbonizes is 8.5 kg / m < ³ >.

(Example 2)
Using the phenol resin PR-55321B (manufactured by Sumitomo Bakelite Co., Ltd.), which is a thermosetting resin, as a raw material, the following steps (a) to (f) were performed in order, and the negative electrode material 2 was obtained.

(A) 510 g of thermosetting resin was spread and allowed to stand as thin as possible in a heat treatment furnace having a furnace internal volume of 60 L (length 50 cm, width 40 cm, height 30 cm). Thereafter, the temperature was raised from room temperature to 500 ° C. at 100 ° C./hour without any of reducing gas replacement, inert gas replacement, reducing gas flow, and inert gas flow.

(B) Next, degreasing treatment was performed at 500 ° C. for 2 hours without cooling gas replacement, inert gas replacement, reducing gas flow, and inert gas flow, and then cooled.

(C) The obtained powder was finely pulverized with a vibration ball mill.
(D) Thereafter, 204 g of the obtained powder was spread and allowed to stand as thin as possible in a heat treatment furnace having a furnace volume of 24 L (length 40 cm, width 30 cm, height 20 cm). Subsequently, the temperature was raised from room temperature to 1200 ° C. at 100 ° C./hour under inert gas (nitrogen) substitution and circulation.

(E) Under an inert gas (nitrogen) flow, it was kept at 1200 ° C. for 8 hours and carbonized.
(F) Under natural gas (nitrogen) circulation, the mixture was naturally cooled to 600 ° C., and then cooled from 600 ° C. to 100 ° C. at 100 ° C./hour.

In addition, the occupation ratio of the raw material with respect to the space which carbonizes is 8.5 kg / m < ³ >.

(Example 3)
A negative electrode material 3 was produced in the same manner as in Example 2 except that the occupation ratio of the raw material with respect to the space to be carbonized was changed to 3.5 kg / m ³ .

Example 4
A negative electrode material 4 was produced in the same manner as in Example 2 except that the occupation ratio of the raw material to the space for carbonization treatment was changed to 0.9 kg / m ³ .

(Example 5)
A negative electrode material 5 was produced in the same manner as in Example 2 except that the occupation ratio of the raw material with respect to the space to be carbonized was changed to 0.5 kg / m ³ .

(Comparative Example 1)
A negative electrode material 6 was produced in the same manner as in Example 1 except that the occupation ratio of the raw material with respect to the space to be carbonized was changed to 16 kg / m ³ .

(Comparative Example 2)
A negative electrode material 7 was produced in the same manner as in Example 2 except that the occupation ratio of the raw material to the space for carbonization was changed to 16 kg / m ³ .

  Various evaluations described above were performed on the negative electrode materials 1 to 7 obtained in the above examples and comparative examples. The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 10 Lithium ion battery 12 Negative electrode active material layer 13 Negative electrode 14 Negative electrode collector 16 Electrolyte 18 Separator 20 Positive electrode active material layer 21 Positive electrode 22 Positive electrode collector

Claims (14)

A negative electrode material for a lithium ion battery having a (002) plane average layer spacing d ₀₀₂ of 0.340 nm or more obtained by X-ray diffraction using CuKα rays as a radiation source and carbonizing the resin composition. There,
After holding the negative electrode material for 120 hours under conditions of a temperature of 40 ° C. and a relative humidity of 90% RH,
Using a thermogravimetric measuring device,
(A) holding the negative electrode material at a temperature of 130 ° C. under a nitrogen atmosphere for 1 hour;
(B) The step of measuring the weight loss of the negative electrode material by heating the negative electrode material after the step (A) at a temperature of 10 ° C./min from a temperature of 40 ° C. to 540 ° C. in a nitrogen atmosphere;
In order,
The weight of the negative electrode material after the step (A) is X,
The weight of the negative electrode material at 150 ° C. in the step (B) is Y ₁ ,
When the weight of the negative electrode material at 250 ° C. in the step (B) is Y ₂ ,
_{100 × (Y 1 -Y 2)} / X chemisorbed water ratio A defined by the 0.5% or less, the negative electrode material for lithium ion batteries. The negative electrode material for a lithium ion battery according to claim 1,
A negative electrode material for a lithium ion battery, wherein the chemical adsorption water ratio A is 0.3% or less. The negative electrode material for a lithium ion battery according to claim 1 or 2,
A negative electrode material for a lithium ion battery, wherein 100 × (XY ₂ ) / X is 0.6% or less. The negative electrode material for a lithium ion battery according to any one of claims 1 to 3,
When the weight of the negative electrode material at 500 ° C. in the step (B) is Y ₃ ,
A negative electrode material for a lithium ion battery, wherein the chemical adsorption water ratio B defined by 100 × (Y ₂ -Y ₃ ) / X is 1.0% or less. The negative electrode material for a lithium ion battery according to claim 4,
A negative electrode material for a lithium ion battery, wherein 100 × (XY ₃ ) / X is 1.6% or less. The negative electrode material for a lithium ion battery according to any one of claims 1 to 5,
After holding the negative electrode material for 120 hours under conditions of a temperature of 40 ° C. and a relative humidity of 90% RH,
The negative electrode material is preliminarily dried by holding it at a temperature of 130 ° C. for 1 hour under a nitrogen atmosphere, and then the moisture generated by holding the negative electrode material after the preliminary drying at 200 ° C. for 30 minutes is Karl Fischer. When measured by coulometric titration,
The negative electrode material for a lithium ion battery, wherein the amount of water generated from the negative electrode material after the preliminary drying is 0.20% by mass or less with respect to 100% by mass of the negative electrode material after the preliminary drying. The negative electrode material for a lithium ion battery according to any one of claims 1 to 6,
A negative electrode material for a lithium ion battery, having a specific surface area of 1 m ² / g or more and 15 m ² / g or less by a BET three-point method in nitrogen adsorption. The negative electrode material for a lithium ion battery according to any one of claims 1 to 7,
A negative electrode material for a lithium ion battery, wherein an adsorption amount of carbon dioxide gas is less than 10 ml / g. The negative electrode material for a lithium ion battery according to any one of claims 1 to 8,
A negative electrode material for a lithium ion battery, wherein the halogen content is less than 50 ppm.   The negative electrode active material containing the negative electrode material as described in any one of Claims 1 thru | or 9. The negative electrode active material according to claim 10,
A negative electrode active material further comprising a negative electrode material of a type different from the negative electrode material. The negative electrode active material according to claim 11,
A negative electrode active material, wherein the different types of negative electrode materials are graphite materials.   The negative electrode for lithium ion batteries containing the negative electrode active material as described in any one of Claims 10 thru | or 12.   A lithium ion battery comprising at least the negative electrode for a lithium ion battery according to claim 13, an electrolyte, and a positive electrode.

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