JP3014303B2 - Method for evaluating carbon material for battery, apparatus therefor, and method for manufacturing battery using same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a carbon material for a battery negative electrode, and more particularly, to a contact heat (immersion heat) obtained by contacting a carbon material for a lithium ion type battery negative electrode with various organic solvents. The present invention relates to a method for evaluating the electrode capacity characteristics of the carbon material based on the above, an apparatus therefor, and a method for manufacturing a battery using the carbon material evaluated thereby.

[0002]

2. Description of the Related Art Conventionally, various carbon materials have been used as a negative electrode carbon material in a lithium ion type battery.
It is roughly classified into three types: non-graphitizable carbon materials that are not easily graphitized by about 3000 ° C.), graphitizable carbon that is easily graphitized, and graphite-based carbon that has already been graphitized before treatment. All of these carbons have a layered structure having a hexagonal network structure formed by carbon atoms, that is, a graphite structure, but the manner of stacking of the hexagonal network structure differs depending on the type of carbon, and more generally, It differs for each production lot.

In a lithium ion battery, lithium ions enter and exit between layers of the negative electrode carbon crystal, that is, between layers of a hexagonal network structure, during charging and discharging, so that the properties of the hexagonal network structure and the layered structure formed by the hexagonal network structure are increased. The difference is an important evaluation point of carbon materials. In fact, the evaluation of the negative electrode carbon material for a lithium ion battery has been performed based on the geometrical structure, that is, the physical structure of the carbon material. Specifically, the physical structure of the carbon material was investigated by X-ray diffraction and / or Raman spectroscopy, and the carbon material was evaluated based on the obtained data.

From the pattern and spread data of the diffraction line obtained by using the X-ray diffraction method, the degree of graphitization, the crystallite size, the surface distance of the hexagonal network structure, and the graphite structure in the carbon material to be diffracted are obtained. Etc. can be evaluated. Here, the evaluation of the graphite structure means the distinction between the ABAB type and the ABC type, or the determination of the mixing ratio of those types. Among these properties, emphasis is placed on the surface distance of a hexagonal mesh structure (mesh plane), which is an index of the interlayer distance. For example, the surface distance d (002) in the C-axis direction of a graphite structure is used as an index. A carbon material having a value of 0.337 nm or less is recommended (JP-A-6-207).
No. 21).

[0005] In the case of using the Raman spectroscopy, the intensity ratio of the spectral lines of the specific Raman scattered light are important, for example, the intensity ratio of 1360 cm ^-1 and 1580 cm ^-1 is 0.4 or more It is recommended that carbon materials be suitable (see JP-A-6-236754). Here, the scattered radiation in the 1580 cm ^-1 corresponds to the vibration modes of the graphite structure, and scattered radiation in the 1360 cm ^-1 corresponds to the vibration mode in which a forbidden in graphite structure a vibration mode in the non-graphitic structure From this, it is considered that the intensity ratio of these two Raman spectra indicates the existence ratio of the graphite structure and the non-graphite structure.

[0006]

However, as described above, only the evaluation method based on the physical structure of the carbon material mainly using the X-ray diffraction method and / or the Raman spectroscopy requires the negative electrode carbon for the lithium ion type battery. In the quality control of material selection and / or production lots and the quality control of lithium ion batteries manufactured using those carbon materials, it is hard to say that a sufficiently reliable evaluation can be made. At present, it is necessary to actually manufacture batteries and evaluate and sort their performance.

This is considered to be due to the following reasons. Lithium ions exist in a state surrounded by organic solvent molecules, that is, in a solvated state, in an electrolytic solution composed of an organic solvent and an inorganic salt. Therefore, when lithium ions enter between layers of the hexagonal network structure of the negative electrode carbon material in the negative electrode of the lithium ion type battery, it is necessary to undergo a chemical reaction for removing all or a part of the solvated organic solvent molecules on the carbon surface. .
The chemical properties of the carbon surface structure, such as the affinity between the carbon surface and the organic solvent, greatly affect the ease of occurrence of this chemical reaction. However, such a chemical property of the carbon surface cannot be evaluated by a conventional physical structure evaluation method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. The present invention evaluates the chemical characteristics of a carbon material for a lithium ion type battery, and particularly controls the quality of the carbon material and a lithium-based material using the carbon material. It is an object of the present invention to provide a sufficiently reliable chemical evaluation method of carbon material and an apparatus for the same, which can evaluate the battery characteristics of a carbon material without producing a battery in quality control of an ion type battery. .

It is another object of the present invention to provide a method for manufacturing a lithium ion battery using a carbon material selected based on the chemical evaluation method of the present invention as a negative electrode material of the lithium ion battery.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned problems. As a result, the present inventors have measured the contact calorie between a carbon material and various organic solvents, and determined various contact calories based on the obtained contact calories. By calculating the value, for example, the calorific value ratio and the adsorption surface area ratio, it is possible to evaluate the chemical characteristics of the carbon material, and further measure the electrode capacity characteristics of the carbon material in a battery manufactured using the material, By investigating the correlation between the chemical characteristics of the above and the electrode capacity characteristics, it was found that an index that can be used for evaluating the carbon material for batteries was obtained, and the present invention was completed.

Thus, according to the present invention, the contact heat obtained by measuring the contact heat between the carbon material and various organic solvents and the value calculated therefrom, such as the calorific value ratio and the adsorption surface area ratio, are evaluated in advance. Based on the correlation between the chemical characteristics of the carbon material obtained and the electrode capacity characteristics of the carbon material previously investigated using a battery manufactured using the material, the contact heat between the carbon material and various organic solvents was used as an index. To determine the quality of the electrode capacitance characteristics of the carbon material,
A method and an apparatus for evaluating a carbon material for a battery are provided.

Further, there is provided a method of manufacturing a lithium ion battery, which is manufactured using the carbon material evaluated and selected by the evaluation method of the present invention.
In this specification, the term solvent is used to include all compounds in a gaseous, liquid or solid state or a mixture of compounds that react with carbon.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention is based on the following findings. The surface of a carbon material has various chemical properties due to various residual functional groups and the like for each type and production lot. Such chemical properties include:
The absolute amounts of the donor and acceptor moieties in hydrogen bonds and their ratios, and the area of the bottom of the graphite structure where the hexagonal network structure, which is considered to cause weak chemical bonding involving π electrons, appears, For example, the ratio to the area of the edge surface, which is considered to cause a relatively strong chemical bond due to the large number, can be mentioned. These properties determine the reactivity of the carbon material with various organic solvents. For example, a carbon material having a large number of hydrogen bond acceptor moieties is highly reactive with a certain type of organic solvent and generates a large amount of contact heat, but not so reactive with another organic solvent and generates contact heat. Not so much.

Therefore, it is considered that the difference in the chemical properties of various carbon materials can be clarified by measuring the difference in contact heat generated when various carbon materials are brought into contact with various organic solvents. That is, whether or not a certain carbon material has desirable chemical properties as a battery negative electrode material is evaluated based on data obtained by measuring the amount of contact heat generated by bringing the carbon material into contact with an organic solvent. It is possible.

Furthermore, an appropriate battery was actually manufactured using the carbon material, and the electrode capacity characteristics of the negative electrode carbon material in the battery were measured. The obtained measured value was compared with the contact between the carbon material and various organic solvents. An index suitable for evaluating a carbon material can be obtained by clarifying a calorific value and a correlation between the calorific value and a value calculated therefrom, for example, a calorific ratio, an adsorbing solvent amount, an adsorbing surface area, and an adsorbing surface area ratio.

As the organic solvent used in the present invention, an organic solvent having a melting point of 20 ° C. or less and a boiling point of 50 ° C. or more is preferred because of easy handling. Further, the type of organic solvent that can be used in the evaluation method of the present invention is not particularly limited as long as it can react with carbon, but usually,
Solvents commonly used as electrolyte solvents for batteries, for example, linear hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, alcohols, ketones, ethers, carbonates, sulfoxides,
Alkyl cyanide and pyridine are preferably used.

Hexane (C ₆ H ₁₄ : boiling point 68 ° C.) can be exemplified as a preferable linear hydrocarbon used in the method of the present invention. If the boiling point of the straight-chain hydrocarbon is higher than room temperature, it is advantageous because it can be handled as a liquid at room temperature, but at a boiling point of about pentane (C ₅ H ₁₂ : 36 ° C.), a measurement error due to heat of vaporization occurs. A straight-chain hydrocarbon having a carbon number equal to or more than hexane is convenient for handling because it is easy to handle.

Further, as the number of carbon atoms in the straight-chain hydrocarbon increases, the heat of contact with carbon increases (JHClinte;
Chem. Soc. Faraday Tr.1, vol.69 (1973), p.1320
Hexane (C ₇ H ₁₆ ) or higher is preferred, but hexane is most preferable because the liquid viscosity at room temperature is high and the ease of handling is somewhat inferior.

[0019] However, a linear long chain hydrocarbons, alone linear hydrocarbon having about 28 to 36 carbon atoms are solids at room temperature in a solution dissolved in hexane, for example, dotriacontanoic (C ₃₂ H ₆₆ ) was dissolved in hexane at 2% by weight (hereinafter referred to as a 2% dotriacontane / hexane solution) and brought into contact with the carbon material to form a long linear carbonized hydrocarbon chain such as dotriacontane. Since the adsorption of hydrogen occurs prior to the adsorption of hexane and shows a behavior different from that of hexane alone, such a solution can also be suitably used in the evaluation method of the present invention.

The cyclic hydrocarbon used in the present invention includes:
Cyclic hydrocarbons having about 6 carbon atoms can be mentioned, and among them, the use of a cyclic hydrocarbon having a chair-shaped structure is convenient for evaluating a rough surface structure, and among those having such a structure, easy handling is possible. Cyclohexane (boiling point: 81 ° C.) can be suitably used.

The aromatic hydrocarbon used in the present invention is an aromatic hydrocarbon having about 6 carbon atoms, among which, it has π electrons and has a molecular structure almost identical to one of the hexagonal network structures on the bottom surface of the graphite structure. Therefore, benzene (boiling point: 80 ° C.), which preferentially adsorbs on the bottom surface of the graphite structure, is preferable.

The above cyclohexane and benzene both have a higher boiling point than hexane and are the most basic compounds having no substituents, so that their behavior can be simplified, so that the present invention can be simplified. It can be suitably used for the method of.

Further, pyridine, which is a six-membered heterocyclic compound exhibiting behavior similar to aromatics, also has a high donor number (W. Gutman; Electrochim., Vol . 21 (1976), p. 661).
Therefore, it is an organic solvent suitable for evaluating electron transfer reactivity.

By using normal butanol and tertiary butanol as the alcohols used in the present invention, it is possible to evaluate the effect of the conformation, and these can be suitably used. Trifluoroethanol can also be suitably used in the present invention, but this compound is a perfect hydrogen bond donor (RWTaft et al.,
J. Solution Chem., Vol . 14 (1985), p. 153), so that the hydrogen bond acceptor portion of carbon can be evaluated by using this.

In the present invention, by using ketone, ether or carbonate, it is possible to evaluate the easily oxidizable portion present on the carbon surface by utilizing the interaction between oxygen contained in the molecule and carbon. Ketones, ethers or carbonates that can be used in the present invention include acetone (boiling point 56 ° C.); tetrahydrofuran (boiling point 66 ° C.), dipropyl ether (boiling point 90 ° C.), dibutyl ether (boiling point 142 ° C.); and propylene carbonate, respectively. (Boiling point: 242 ° C.), dimethyl carbonate (boiling point: 90 ° C.), methyl ethyl carbonate (boiling point: 107 ° C.), diethyl carbonate (boiling point: 126 ° C.), and the like. Among these, propylene carbonate, which is one of the main battery solvents and has a high boiling point and is easy to handle, can be suitably used.

Similarly, in the present invention, by using a sulfoxide and an alkyl cyanide, a portion acting as a cation on a carbon surface is evaluated by utilizing the nucleophilicity of a sulfonic acid group and a cyano group of the sulfoxide and the alkyl cyanide group. Can be. Examples of the sulfoxide that can be used in the present invention include dimethyl sulfoxide (boiling point: 189 ° C.) and diethyl sulfoxide (boiling point: 90 ° C.), and alkyl cyanide includes acetonitrile (boiling point: 82 ° C.) and propiononitrile (boiling point: 97 ° C.) can do.

The measurement of the contact heat between the various organic solvents described above and the carbon to be evaluated can be performed as follows. First, a measuring container of a twin calorimeter equipped with a blade which can be operated from the outside is filled with an organic solvent, and the sealed carbon is immersed in a polyethylene bag and sealed therein. Then, the measurement container and the reference container are left at room temperature until they reach an isothermal state. After the two have reached the isothermal state, the cutting tool is operated from the outside to break the polyethylene bag containing carbon, thereby mixing the carbon with the organic solvent and measuring the generated contact heat.

At this time, if the contact heat is small compared to the heat of vaporization of the organic solvent, the airtightness of the measurement container greatly affects the accuracy of the contact heat measurement. Cost. In order to obtain sufficient airtightness, the lid of the measuring container is desirably a threaded seal having an O-ring seal. Further, it is desirable to select the type of the sealing material of the O-ring seal according to the type of the organic solvent to be used so that sufficient airtightness is always maintained.
Within the range of the following examples, good airtightness can be obtained by using an O-ring seal made of butyl rubber.

From the calorific value of the contact between the carbon material and various organic solvents measured as described above, the calorific ratio, the amount of each organic solvent adsorbed, the adsorbed surface area and the adsorbed surface area ratio can be determined. In addition, the electrode performance can be investigated by preparing an appropriate battery using the test carbon material according to a conventional method. By examining the correlation between various measured values and calculated values obtained in this way, it is possible to clarify the chemical characteristics of the carbon material and determine an index for evaluating the carbon material. And
Based on the index, a carbon material suitable for manufacturing a battery having desired battery performance can be selected, and a battery can be manufactured using the material.

However, as described above, carbon materials are roughly classified into three types based on the crystal structure. Therefore, when examining an evaluation index obtained by measuring the amount of heat of contact between the carbon material and various organic solvents, However, it is necessary to perform this for each type of carbon material. Further, the evaluation method of the present invention can be performed using only one kind of organic solvent. However, by using two or more kinds of organic solvents, a more accurate evaluation result can be obtained. It is preferred to carry out the method of the invention using a solvent. The following examples illustrate the invention in more detail.

[0031]

【Example】

Embodiment 1 FIG. Six types of non-graphitizable carbon shown in Table 1 below were used as carbon materials.
Have different starting material (base / crosslinking agent) ratios, and A1
And A2, B1 and B2, and C1 and C2 have different processing temperatures when producing carbon materials. First, these six types of carbon materials were subjected to X-ray diffraction. The result is shown in FIG. As can be seen in FIG. 1, the strong diffraction line is the angle of the (002) plane diffraction line (26.3 using CuKα ray).
Degree), and the half-width of the diffraction line is about 20 times larger than that of normal graphite, so that the test sample has a large interlayer spacing and It can be seen that there is a feature that the range of spread is large. Further, since two diffraction lines of (100) plane diffraction line and (101) plane diffraction line observed around 42 to 44 degrees in ordinary graphite are not separated, the structure of the test carbon material is a graphite structure. You can see that it is far away from Thereby, it was confirmed that the six types of carbon materials tested were non-graphitizable carbon.

Next, the amount of heat of contact between the test carbon material and the ten kinds of organic solvents shown in Table 1 was measured by the above-described method using a twin calorimeter. Hexane, benzene, normal butanol,
The measurement results of trifluoroethanol and methyl sulfoxide are shown, and the resulting contact calories (mJ / g) are shown in Table 1 below.
Shown in The meanings of the abbreviations used in the tables and figures in this specification are as follows. H: Hexane B: Benzene cH: Cyclohexane tBt: Tertiary butanol nBt: Normal butanol Py: Pyridine TFE: Trifluoroethanol DMSO: Dimethyl sulfoxide PC: Propylene carbonate Dc / H: 2% dotriacontane / hexane solution

[0033]

[Table 1]

Table 1 does not show the endothermic amount of endotherm that appears after the generation of contact heat when the carbon material is brought into contact with trifluoroethanol and pyridine. Table 2 below summarizes the correlation coefficients between the organic solvents.

[0035]

[Table 2]

From Table 2 above, it can be seen that the combinations showing a high negative correlation are three combinations of hexane-normal butanol, hexane-trifluoroethanol and hexane-benzene. In the combination showing such a negative correlation, it is considered that one organic solvent evaluates a portion having a contradictory property on the surface of the carbon material with the other organic solvent. For example, when a certain organic solvent evaluates the bottom surface of the graphite structure and another organic solvent evaluates the edge surface, a relationship such that the ratio of the edge surface decreases as the ratio of the bottom area increases, that is, a negative relationship. It is considered that a correlation occurs. That is, it is considered that hexane, normal butanol, trifluoroethanol, and benzene evaluate a portion having a contradictory property on the surface of the carbon material.

On the other hand, combinations showing a positive correlation are three combinations of benzene-trifluoroethanol, benzene-dimethylsulfoxide and dimethylsulfoxide-trifluoroethanol. It is considered that these are evaluating portions having similar properties on the surface of the carbon material.

BET surface area (m ² / g) of each sample according to a conventional method
A1: 17.8, A2: 19.4, B1: 9.9.
93, B2: 9.18, C1: 20.2, C2: 5.68. Table 3 shows the correlation between the calorific value of the contact heat and the BET surface area of the carbon material.

[0039]

[Table 3]

From Table 3 above, the carbon material was hexane,
Calorific value of contact heat generated by contact with benzene, trifluoroethanol and dimethyl sulfoxide (mJ / g)
Has a high correlation with the BET surface area, that is, the adsorption of these organic solvents depends on the surface area value.
Furthermore, the calorific value (mJ / m2) of the 2% dotriacontan / hexane solution obtained by converting the contact calorific value (mJ / g) per unit area
² ) also shows a high correlation with the BET surface area.

Next, using a test carbon material (2 g) as a negative electrode and LiCoO ₂ (5 g) as a positive electrode active material, 1M perchloric acid in a 1: 1 mixed solvent of ethylene carbonate and dimethoxymethane was used as an electrolytic solution. A cylindrical battery having a size of 2 / 3A was produced using lithium dissolved therein.
This battery was subjected to a charge / discharge cycle test, and the first charge capacity, the first discharge capacity, the difference between them (capacity loss), and the discharge capacity (2) when charged to a voltage lower than usual were measured. Table 4 shows a correlation coefficient between the obtained measured value and the contact calorific value shown in Table 1 above.

[0042]

[Table 4]

From Table 4 above, it can be seen that the first discharge capacity of the battery has a high correlation with the contact heat of many organic solvents. Organic solvents that showed a high correlation with the first discharge capacity were hexane, benzene, trifluoroethanol, dimethyl sulfoxide, and normal butanol. The only organic solvent shown was hexane. FIG. 9 shows the relationship between the first discharge capacity and the contact heat of benzene (mJ / g), and FIG. 10 shows the relationship between the first discharge capacity and the contact heat of trifluoroethanol (mJ / g). These figures also show that the first discharge capacity has a positive correlation with benzene and trifluoroethanol, and that the larger the contact calorific value of these organic solvents, the larger the first discharge capacity.

On the other hand, when the battery is charged to a voltage lower than normal to obtain a large capacity, the correlation between the discharge capacity and these organic solvents is lower than when the battery is charged to the normal charging voltage. However, dimethyl sulfoxide still maintained a high correlation. FIG. 11 shows the relationship between the discharge capacity when charged to a voltage lower than usual and the contact heat (mJ / g) of dimethyl sulfoxide. This figure also shows that there is a positive correlation between them, and that the discharge capacity increases as the contact heat of dimethyl sulfoxide increases.

On the other hand, two kinds of organic solvents, cyclohexane and tertiary butanol, whose conformations are more complicated than those of the above five kinds of organic solvents, have a high negative correlation with the first charge capacity and capacity loss. Showed sex. FIG. 7 shows the relationship between the first charging capacity and the contact heat of tertiary butanol (mJ / g), and FIG. 8 shows the relationship between the capacity loss and the contact heat of cyclohexane (mJ / g). As can be seen from these figures, the relationship between the first charge capacity and the tertiary butanol and the relationship between the capacity loss and cyclohexane are both negatively correlated, and as the contact calorific value of these organic solvents increases, the first charge capacity or It can be seen that the capacity loss is reduced. Next, Table 5 shows the correlation coefficient between the measured electrode capacitance characteristic value and the calorific value (mJ / m ² ) obtained by converting the contact calorific value (mJ / g) used in Table 4 per unit area.

[0046]

[Table 5]

From the above Table 5, when the amount of contact heat is converted into the amount of heat per unit area (mJ / m ² ), the discharge capacity and the three kinds of organic solvents of tertiary butanol, pyridine and a 2% dotriacontane / hexane solution are compared. It can be seen that the correlation of was improved. FIG. 12 shows the relationship between the discharge capacity when charged to a voltage lower than normal and the contact heat (mJ / m ² ) of tertiary butanol. This figure also shows that there is a negative correlation between them, and that the discharge capacity decreases as the contact heat of tertiary butanol increases.

The relationship between the electrode capacitance characteristics of the non-graphitizable carbon material and the contact heat between the carbon material and each organic solvent as described above can be summarized as follows. I) The first charge capacity is the contact calorie of tertiary butanol (mJ /
g) has a negative correlation with g); b) the first discharge capacity has a positive correlation with the contact calorie (mJ / g) of trifluoroethanol, benzene and dimethyl sulfoxide, and the contact calorie of hexane (MJ / g) and negative correlation; c) Capacity loss is the contact calorie of cyclohexane (mJ / g)
And d) the discharge capacity when charged to a voltage lower than normal is
Contact heat of tertiary butanol, pyridine and 2% dotriacontane / hexane solution having a positive correlation with dimethyl sulfoxide and converted to a value per unit area (mJ
/ m ² ). These correlations can be used as an index for evaluating the carbon material. Further, from the measured calorific value, various values, such as a calorific value ratio, a solvent adsorption amount, an adsorption surface area and an adsorption surface area ratio, are calculated, and the correlation between them and various electrode capacitance characteristic values is investigated. Index can also be obtained.

Here, the amount of adsorption (μmol / g or μmol / m ² ) is obtained by dividing the obtained contact calorific value (mJ / g or mJ / m ² ) by the heat of adsorption (mJ / μmol). And the calorific value multiplied by the adsorption area value (m ² / μmol) gives the adsorption surface area (m ² / g or m ² / m ² ). For the organic solvent used in this example, the heat of adsorption and the adsorption area have already been reported (EM Arnett, BJ Huchin
son & MH Healy, J. American Chem. Soc., Vol . 110
(1988), p. 5255; PA Elkington & G. Curthoys, J.
Phys. Chem., Vol . 73 (1969), p. 2321; AL McClell
an & HF Harnsberger, J. Colloid Interface Sci.,
Vol. 23 (1967), p. 577), and these values were used to determine the adsorption amount and adsorption surface area of each organic solvent. The heat of adsorption and the adsorption area used in the calculation are shown in Table 6 below. However, no report on tertiary butanol was found, so the calculation was performed by substituting the value of normal butanol. For normal butanol and dotriacontan, the following Groszek conversion formula (AJ Groszek; Ca
rbon, Vol.25 (1987), p.717). Normal butanol: 1 J / g = 6.7 m ² / g Dotriacontan: 1 J / g = 19.3 m ² / g

[0050]

[Table 6]

Next, Table 7 below shows the calculation results of the adsorption amount of each organic solvent, and Table 8 shows the calculation results of the adsorption surface area of each organic solvent.

[0052]

[Table 7]

[0053]

[Table 8]

When various adsorption area ratios were determined from the values obtained in Table 8, some of the adsorption surface area ratios had a high correlation with the first discharge capacity (mAh / g). I was
Table 9 below shows such adsorption surface area ratios and correlation coefficients between them and the first discharge capacity.

[0055]

[Table 9]

Since the adsorption surface area ratio shown in Table 9 above has a high correlation with the first discharge capacity, by obtaining these adsorption surface area ratios, it is possible to obtain the desired first surface area using the non-graphitizable carbon material to be tested. It can be evaluated whether or not the discharge capacity can be obtained. That is, the adsorption surface area ratio TFE / (TFE +
H), DMSO / (DMSO + H), nBt / (H + nBt) and B / (B + H) are
It is an index for evaluating non-graphitizable carbon materials. Table 9
As shown in the above, the calorific value ratio B / (B + H) also shows a high positive correlation with the first discharge capacity, indicating that it can be used as an evaluation index. Further, it can be seen that when the heat quantity ratio is 0.5 or more, a high first discharge capacity is exhibited.

FIG. 13 is a graph in which the abscissa is the adsorption surface area ratio B / (B + H) and the ordinate is the first discharge capacity. By using this figure, the ratio of adsorption surface area that the carbon material should satisfy when obtaining a specific first discharge capacity B / (B + H)
Is determined, and only such a test carbon material is selected to manufacture a battery. In the present example and the following examples, the adsorption surface area ratio of various organic solvents is illustrated as a calculated value that can be used as an evaluation index of a carbon material. However, as described above, the adsorption surface area is obtained by multiplying a calorific value by a coefficient. It is clear that the calculated value is proportional to the calorific value, and thus, similarly to the adsorption surface area ratio, other calculated values such as the calorific value ratio or the adsorption amount ratio of various organic solvents can be used as the evaluation index. .

Embodiment 2 FIG. As a carbon material, the following Table 1
In the table, six types of graphitizable carbon, ie, mesophase carbon microbeads (hereinafter, may be abbreviated as MCMB), were used. Oxygen concentration and processing time). First, these six types of carbon materials were subjected to X-ray diffraction. The result is shown in FIG.
As shown in FIG. 14, the mirror index of the obtained diffraction line matches that of hexagonal graphite, so that the test sample has a certain degree of graphite structure, that is, the six types of carbon materials tested have It turns out that it is graphitizable carbon. In the drawing, the diffraction line observed near 13 degrees is likely to be a (001) plane diffraction line. From these X-ray diffraction results, 6
The difference between the types of samples is hardly known.

Next, the contact heat between the test carbon material and the ten kinds of organic solvents shown in Table 10 below was measured by the above-described method using a twin calorimeter. FIG.
18 each with benzene, trifluoroethanol,
The measurement results of a normal butanol and a 2% dotriacontane / hexane solution are shown, and the obtained contact heat (mJ /
g) and the correlation between these values and the BET surface area (m ² / g) are shown in Table 10 below. The BET surface area was determined according to a conventional method, and was as follows: M1: 3.14, M2: 3.34, M3: 2.
99, M4: 3.02, M5: 3.23 and M6: 4.28.

[0060]

[Table 10]

Table 10 above does not show the endothermic amount of endotherm that appears after the generation of contact heat when the carbon material is brought into contact with trifluoroethanol and pyridine. As seen in Table 10, unlike the non-graphitizable carbon material, the correlation with the BET surface area is not very high, but this is considered to be due to the difference in the surface state. However, benzene and normal butanol show a slightly higher correlation. Next, Table 11 below summarizes the correlation coefficients between the respective organic solvents.

[0062]

[Table 11]

From Table 11 above, the combinations showing high correlation are only the three combinations of hexane-trifluoroethanol showing negative correlation and propylene carbonate-cyclohexane and propylene carbonate-normal butanol showing positive correlation. It can be seen that it is. Among these, the combination of hexane-trifluoroethanol showed a high correlation even in non-graphitizable carbon materials.

Next, using a test carbon material (2 g) as a negative electrode and LiCoO ₂ (5 g) as a positive electrode active material, 1 M perchloric acid in a 1: 1 mixed solvent of ethylene carbonate and dimethoxymethane was used as an electrolytic solution. A cylindrical battery having a size of 2 / 3A was prepared using a material in which lithium was dissolved.
This battery was subjected to a charge / discharge cycle test, and the first charge capacity, the first discharge capacity, and the difference between them (capacity loss) were measured. The correlation coefficient between the obtained measured value and the contact calorific value (mJ / g) shown in Table 10 above is shown in Table 12 below.

[0065]

[Table 12]

From Table 12 above, the three types of organic solvents having a high correlation with the first charge capacity of the battery were tertiary butanol, trifluoroethanol and a 2% dotriacontane / hexane solution. It turns out that it showed a positive correlation. Further, all of these three types of organic solvents have a positive correlation with the capacity loss. further,
It can be seen that the tertiary butanol and 2% dotriacontane / hexane solution also have a positive correlation with the first discharge capacity.

FIG. 19 shows the relationship between the electrode capacity characteristics and the contact heat (mJ / g) of a 2% dotriacontane / hexane solution.
0 shows the relationship between the electrode capacity characteristic and the contact heat (mJ / g) of tertiary butanol, respectively. From these figures, it can also be seen that the contact heat (mJ / g) of the 2% dotriacontane / hexane solution has a high positive correlation with all electrode capacity characteristics, and that of tertiary butanol (mJ / g). Have a high positive correlation with the first charge capacity and the capacity loss, and as the contact calorific value (mJ / g) of these organic solvents increases, their electrode capacity characteristic values also increase. Understand.

Next, the correlation coefficient between the measured electrode capacitance characteristic value and the calorific value (mJ / m ² ) obtained by converting the contact calorific value (mJ / g) used in Table 12 into unit area is shown in Table 13. Shown in

[0069]

[Table 13]

From Table 13 above, when the amount of contact heat is converted into the amount of heat per unit area (mJ / m ² ), high correlation is recognized because the first charge capacity, the first discharge capacity, and the capacity loss. It can be seen that the benzene and 2% dotriacontan / hexane solution and the first charge capacity and capacity loss are only between the hexane and the hexane.

The relationship between the electrode capacity characteristics of the graphitizable carbon material and the contact heat between the carbon material and each organic solvent as described above can be summarized as follows. I) The first charge capacity is the contact heat of tertiary butanol (mJ
/ g), contact heat of trifluoroethanol (mJ / g), 2%
It has a positive correlation with the contact heat of dotriacontan / hexane solution (mJ / g or mJ / m ² ), and also the contact heat of hexane (mJ / m ² ) and the contact heat of benzene (mJ / m ² ) B) the first discharge capacity is the contact calorie of tertiary butanol (mJ
/ g) and the contact calorie (mJ / g or mJ / m ² ) of a 2% dotriacontane / hexane solution, and the contact calorie of benzene (mJ / g or mJ / m ² ) (C) capacity loss is the contact calorie of tertiary butanol (mJ / g)
And 2% dotriacontane / hexane solution, have a positive correlation with the contact calorie (mJ / g or mJ / m ² ), and have the contact calorie of hexane (mJ / m ² ) and benzene (mJ / m ² )
J / g or mJ / m ² ). These correlations can be used as an index for evaluating the carbon material. Further, from the measured calorific value, various values, such as a calorific value ratio, a solvent adsorption amount, an adsorption surface area and an adsorption surface area ratio, are calculated, and the correlation between them and various electrode capacitance characteristic values is investigated. Index can also be obtained.

The adsorption amount and adsorption surface area of each organic solvent were determined in the same manner as in Example 1. Table 14 below shows the calculation results of the adsorption amount of each organic solvent, and Table 15 shows the calculation results of the adsorption surface area of each organic solvent.

[0073]

[Table 14]

[0074]

[Table 15]

Various adsorption area ratios were determined from the values obtained in Table 15 above, and the correlation with the first discharge capacity (mAh / g) was examined. The results are shown in Table 16 below.

[0076]

[Table 16]

As can be seen from Table 16 above, the adsorption surface area ratio B / (B + H), which could be used as an evaluation index, cannot be used for easily graphitizable carbon in non-graphitizable carbon materials. As an index of the evaluation of the graphitizable carbon material, the adsorption surface area ratio B / (B + nBt), B / (B + Dc / H) and B / (B + tBt) having a high correlation with the first discharge capacity are used. ) Can be used. Also, as shown in Table 16, the calorific value ratio
B / (B + Dc / H) also shows a high negative correlation with the first discharge capacity, indicating that it can be used as an index for evaluation. Further, it can be seen that when the calorific ratio is 0.4 or less, a high first discharge capacity (240 mAh / g or more) is exhibited.
FIG. 21 shows a graph in which the abscissa is the adsorption surface area ratio B / (B + Dc / H) and the ordinate is the first discharge capacity. From this figure, 2
In order to obtain a first discharge capacity of 00 mAh / g or more, it is desirable to manufacture a battery by selecting only carbon materials having an adsorption surface area ratio B / (B + Dc / H) of 0.4 or less. You can see that.

Embodiment 3 FIG. As a carbon material, the following Table 1
The four types of graphite-based carbon shown in Table 7 were used.
To N4 are obtained by crushing natural graphite and classifying them by particle size, and the order of average particle size is N1 <N2 <N
3 <N4. First, these four types of carbon materials were subjected to X-ray diffraction. The result is shown in FIG. As shown in FIG. 22, among the diffraction lines observed between 42 degrees and 45 degrees, the diffraction line near 43.3 degrees is a diffraction line indicating the presence of a rhombohedral structure. In these samples, It seems that some rhombohedral structure is mixed in the hexagonal graphite structure. However, since the diffraction line becomes smaller for a sample having a smaller particle size, it is considered that the content of the rhombohedral structure decreases as the particle size decreases.

Next, the contact heat between the test carbon material and the ten kinds of organic solvents shown in Table 17 below was measured by the above-described method using a twin calorimeter. The resulting contact heat (mJ / g) and their values and BET surface area (m ² /
The correlation with g) is shown in Table 17 below. Where BET above
The surface area was determined according to a conventional method, N1: 13.1, N
2: 8.70, N3: 5.23 and N4: 2.66.

[0080]

[Table 17]

Table 17 does not show the endothermic amount of endotherm that appears after the generation of contact heat when the carbon material is brought into contact with trifluoroethanol and pyridine. As can be seen from Table 17, in the case of graphite-based carbon materials, the amount of contact heat (mJ / g) with many organic solvents has a high correlation with the BET surface area. Closer to non-graphitizable carbon than carbonized,
That is, it is considered that the chemical characteristics of the graphite-based carbon surface are similar to the non-graphitizable carbon. Therefore, when considered in conjunction with the results of X-ray diffraction, it is considered that the graphite-based carbon material has an overall structure closer to the graphitizable carbon material, but the surface chemical characteristics are closer to the non-graphitizable carbon material. Next, Table 18 below summarizes the correlation coefficients between the respective organic solvents.

[0082]

[Table 18]

As shown in Table 18, the characteristics of the graphite-based carbon material are such that although the number of combinations showing a high positive correlation between organic solvents is large, the combinations showing a negative correlation are almost observed. That is not. That is, as shown in Table 17 above, although there is much organic solvent adsorbed according to the BET surface area, almost no negative correlation is observed between the organic solvents. It is considered that the surface structure of the graphite-based carbon material used shows homogeneity such that the bottom surface and the edge surface of the graphite structure cannot be distinguished.

Next, Table 19 below shows the calculation results of the adsorption amount of each organic solvent, and Table 20 shows the calculation results of the adsorption surface area of each organic solvent.

[0085]

[Table 19]

[0086]

[Table 20]

Regarding the electrode capacity characteristics of the graphite-based carbon material, the test carbon material (2 g) was used as a negative electrode, and LiCoO ₂ (5
g) was used as a positive electrode active material, and 1 M lithium perchlorate dissolved in a 1: 1 mixed solvent of ethylene carbonate and dimethoxymethane was used as an electrolytic solution.
A cylindrical battery having a size of / 3 A was prepared, and this battery was subjected to a charge / discharge cycle test, and a first charge capacity, a first discharge capacity,
The investigation was conducted by measuring the difference between the two (capacity loss) and the discharge capacity when charged to a low voltage.

However, since only two types of samples were used, it was not possible to find a correlation between the electrode capacity characteristic of graphite-based carbon and the contact calorific value only from the obtained measured values.
A comparison was made between the electrode capacity characteristics of the non-graphitizable carbon and the graphitizable carbon obtained in Examples 1 and 2 and the correlation between the contact calorific values. As a result, as expected from the results of the contact heat measurement, it was found that the chemical characteristics of the graphite-based carbon surface were closer to non-graphitizable carbon rather than easily graphitic carbon.

FIGS. 23 to 26 show the relationship between the electrode capacity characteristic and the contact calorific value of the non-graphitizable carbon obtained in Example 1 with the measurement results of graphite-based carbon added. . FIG. 23 shows the relationship between the first charge capacity and the contact heat of tertiary butanol (mJ / g) of the battery prepared using the non-graphite carbon material, and the measurement results of graphite-based carbon were added to FIG. It is a diagram showing that the relationship between the first charge capacity of a battery made using a graphite-based carbon material and the contact heat (mJ / g) of tertiary butanol almost coincides with that of non-graphitizable carbon. ing. Although not shown, the non-graphitizable carbon material and the graphite-based carbon material tended to be almost the same in the relationship between the capacity loss and the contact heat of benzene (mJ / g).

FIG. 24 shows the relationship between the first discharge capacity and the contact heat of benzene (mJ / g) of the battery prepared using the non-graphitizable carbon material. FIG. 9 shows the measurement results of the graphite-based carbon. It is a figure added, and also shows that the graphite-based carbon material and the non-graphite-based carbon material have a tendency almost identical in this relationship. However, the measurement results of graphite-based carbon materials showed a different tendency from the relationship between the first discharge capacity of batteries using non-graphitizable carbon materials and the contact heat of trifluoroethanol (mJ / g) (Fig. Not shown).

FIG. 25 shows the discharge capacity (2) when a battery using a non-graphitizable carbon material was charged to a voltage lower than usual, and the contact heat (mJ /
FIG. 12 is a diagram in which the measurement results of graphite-based carbon are added to FIG. 11 showing the relationship with g). Although the measurement results for graphite-based carbon materials tend to almost match the straight lines obtained from the measurement results for non-graphitizable carbon materials, they are located below the straight lines, but this difference is caused by differences in charging conditions. It is thought that it was. Similarly, FIG. 12 shows the relationship between the discharge capacity (2) and the contact heat of tertiary butanol (mJ / m ² ) when the battery using the non-graphitizable carbon material was charged to a voltage lower than usual. FIG. 26 to which the measurement result of the graphite-based carbon material is added also shows that the measurement result of the graphite-based carbon material has a tendency to substantially match the straight line obtained from the measurement result of the non-graphitizable carbon material. I have.

Further, the first discharge capacity and the adsorption surface area ratio B / (B + H) of the battery prepared using the non-graphitizable carbon material
FIG. 13 showing the relationship between the measured values of the graphite-based carbon material was added. The data points were plotted on a straight line obtained from the result of the discharge capacity (2) when the battery was charged to a voltage lower than usual. I knew I could get on (not shown). From the above, it was considered that the chemical characteristics of the graphite-based carbon surface were close to those of non-graphitizable carbon, and the evaluation could be performed according to the non-graphitizable carbon material.

Embodiment 4 FIG. The method for evaluating a carbon material according to the present invention, that is, by measuring the contact heat between any one type of carbon material selected from non-graphitizable carbon material, easily graphitizable carbon material and graphite-based carbon material and a plurality of organic solvents. The obtained contact heat and the value calculated therefrom, for example, the calorific value ratio, the amount of adsorption, the adsorption surface area or the adsorption surface area ratio, and the electrode capacity characteristics of the carbon material obtained by evaluating the battery manufactured using the carbon material Beforehand, and the amount of contact heat between the carbon material and the plurality of organic solvents of the same kind as the carbon material is measured, and based on the correlation checked in advance, the electrode of the test carbon material is used. An apparatus used in a method for evaluating a carbon material for a battery, which is characterized by evaluating capacity characteristics, was produced. FIG. 27 shows the configuration of the device.

In FIG. 27, reference numeral 1 denotes a measuring container of a twin calorimeter, 2 denotes a reference container of the calorimeter, 3 denotes a thermoelectric bank for measuring a temperature difference between the measuring container and the reference container, and 4 denotes a temperature from the thermoelectric bank. An amplifier for amplifying the difference signal, 5 an A / D converter for converting the output signal of the amplifier, 6 an arithmetic unit for integrating the temperature difference signal and converting it into a contact calorific value, and comparing the obtained value;
Is a storage device for storing data for evaluating the carbon material, and 8 is an output device for outputting results. Specifically, the present inventors have described a twin calorimeter (MMC-5111U) manufactured by Tokyo Riko as 1-4, a hybrid recorder (YEW3087) manufactured by Yokogawa Electric as 5, a personal computer manufactured by NEC as 6 and 7, and PC9801DA) and an apparatus using an Epson printer (LP1500) as No. 8 were prepared, and carbon materials were evaluated.

In the measurement by the apparatus according to the present embodiment, one example of non-graphitizable carbon is as follows: 1) The relationship between the adsorption surface area ratio for evaluation and the capacity of the electrode is investigated in advance as shown in FIG. 2) FIGS. 2 and 3 show the amounts of heat when the non-graphitizable carbon material to be tested is brought into contact with benzene and hexane, respectively.
3) calorimetric ratio or adsorption surface area ratio B / (B + H) is calculated from the measured data by an arithmetic unit; and 4) the obtained calorimetric ratio or adsorption surface area ratio is determined by the previously measured adsorption surface area. The evaluation is performed according to a procedure as described above in which the carbon material to be tested is evaluated in light of the relationship between the ratio of the carbon material and the capacity of the electrode using the non-graphitizable carbon material.

FIG. 28 shows a flowchart of the process of evaluating the carbon material. The evaluation standard, that is, the reference line for determining the quality of the carbon material can be arbitrarily set as desired. The present inventors set a judgment center line at a discharge capacity of 250 mAh / g and controlled the quality of the carbon material by a method using a carbon material falling within a range of ± 5% from the center line. The occurrence rate of battery failures due to variations in characteristics between manufacturing lots could be reduced to 1% or less.

Embodiment 5 FIG. A battery was manufactured using the non-graphitizable carbon material and the graphite-based carbon material selected by the evaluation method according to the present invention for a negative electrode. First, the relationship between the contact calorific value of non-graphitizable carbon with benzene and the adsorption surface area ratio B / (B + H) obtained from the contact calorific value with hexane and the first discharge capacity of a battery using non-graphitizable carbon In order to obtain a discharge capacity of 250 mAh / g or more, a graphitizable carbon material and a graphite-based carbon material having an adsorption surface area ratio B / (B + H) of 0.5 or more are selected based on FIG. It was decided to.

Next, according to the method of the present invention, non-graphitizable carbon materials and graphite-based carbon materials satisfying the above conditions were selected. The selected material (2 g) is used as a negative electrode for LiCoO
₂ (5 g) was used as a positive electrode active material, and a 2 / 3A size cylindrical battery using 1M lithium perchlorate dissolved in a 1: 1 mixed solvent of ethylene carbonate and dimethoxymethane was used as an electrolytic solution. Produced. The design capacity of this battery was 500 mAh. FIG. 29 shows a discharge curve of the manufactured battery. As can be seen from FIG. 29, the batteries prepared using the selected non-graphitizable carbon and the graphite-based carbon material both have the designed capacity, and the adsorption surface area ratio B / (B + H) has a non-graphitizable carbon. It was confirmed that it was useful as an index for evaluating materials and graphite-based carbon materials.

Embodiment 6 FIG. A battery was manufactured using the graphitizable carbon material selected by the evaluation method according to the present invention for the negative electrode. First, a battery using adsorbable surface area ratio B / (B + Dc / H) obtained from the contact calorific value of graphitizable carbon with benzene and the contact calorific value with a 2% dotriacontan / hexane solution. Based on FIG. 21 showing the relationship with the first discharge capacity, the adsorption surface area ratio B / (B + Dc / H) was set to 0.4 in order to obtain a discharge capacity of 200 mAh / g or more.
The following easily graphitizable carbon materials were selected.

Next, graphitizable carbon materials satisfying the above conditions were selected according to the method of the present invention. Using the selected material (2.5 g) as a negative electrode and LiCoO ₂ (5 g) as a positive electrode active material, 1 M lithium perchlorate was dissolved in a 1: 1 mixed solvent of ethylene carbonate and dimethoxymethane as an electrolytic solution. A 2 / 3A size cylindrical battery was manufactured using the same. The design capacity of this battery was 500 mAh. FIG. 30 shows a discharge curve of the manufactured battery. Batteries made using the selected graphitizable carbon material show the capacity as designed, and the adsorption surface area ratio B / (B + Dc / H)
Was useful as an index for evaluation of graphitizable carbon materials.

[0101]

According to the method for evaluating a carbon material according to the present invention, it is possible to clarify the chemical characteristics of a carbon material for a negative electrode of a lithium ion type battery and to evaluate battery characteristics without actually manufacturing a battery. Can be. Moreover, the method of the present invention can be performed in a short time and at low cost,
Enables cost reduction of battery production. Further, according to the present invention, a high-performance lithium-ion battery carbon material and a high-performance lithium-ion battery using the same can be provided at low cost and with high reliability based on a chemical evaluation method.

[Brief description of the drawings]

FIG. 1 is a diagram showing X-ray diffraction results of six types of non-graphitizable carbon materials.

FIG. 2 is a view showing the results of measuring the contact heat between six types of non-graphitizable carbon materials and hexane.

FIG. 3 is a diagram showing the results of measuring the contact heat between six types of non-graphitizable carbon materials and benzene.

FIG. 4 is a diagram showing the results of measuring the contact heat between six types of non-graphitizable carbon materials and normal butanol.

FIG. 5 is a diagram showing the results of measuring the contact heat between six types of non-graphitizable carbon materials and trifluoroethanol.

FIG. 6 is a view showing the results of measuring the contact heat between six types of non-graphitizable carbon materials and dimethyl sulfoxide.

FIG. 7 is a diagram showing a first charge capacity of a battery manufactured using six types of non-graphitizable carbon materials, and a relation between contact heat between those materials and tertiary butanol.

FIG. 8 is a diagram showing the initial capacity loss of batteries manufactured using six types of non-graphitizable carbon materials, and the relationship between the contact heat of those materials and cyclohexane.

FIG. 9 is a diagram illustrating first discharge capacities of batteries manufactured using six types of non-graphitizable carbon materials, and a relationship between contact heat between those materials and benzene.

FIG. 10 is a diagram showing first discharge capacities of batteries manufactured using six types of non-graphitizable carbon materials, and a relation between contact heat between those materials and trifluoroethanol.

FIG. 11 shows discharge capacities (2) when batteries manufactured using six types of non-graphitizable carbon materials were charged to a voltage lower than usual, and a relationship between contact heat between those materials and dimethyl sulfoxide. FIG.

FIG. 12 shows the discharge capacity (2) when batteries prepared using six types of non-graphitizable carbon materials were charged to a voltage lower than usual, and the relationship between the contact heat of those materials and tertiary butanol. FIG.

FIG. 13: Discharge capacity and adsorption surface area ratio B / (B + H) of batteries made using six types of non-graphitizable carbon materials
FIG.

FIG. 14 is a diagram showing X-ray diffraction results of six types of graphitizable carbon materials.

FIG. 15 is a diagram showing the results of measuring the contact heat between six types of graphitizable carbon materials and benzene.

FIG. 16 is a diagram showing the results of measuring the contact heat between six types of graphitizable carbon materials and trifluoroethanol.

FIG. 17 is a diagram showing the results of measuring the contact heat between six types of graphitizable carbon materials and normal butanol.

FIG. 18 is a view showing the results of measuring the contact heat between six types of graphitizable carbon materials and a 2% dotriacontane / hexane solution.

FIG. 19 is a diagram showing the capacity of batteries manufactured using six types of graphitizable carbon materials and the relationship between the materials and the contact heat of a 2% dotriacontane / hexane solution.

FIG. 20 is a diagram showing the capacity of batteries manufactured using six types of graphitizable carbon materials and the relationship between the contact heat of those materials and tertiary butanol.

FIG. 21 is a diagram showing a relationship between a discharge capacity and a surface area ratio B / (B + Dc / H) of batteries manufactured using six types of graphitizable carbon materials.

FIG. 22 is a diagram showing X-ray diffraction results of four types of graphite-based carbon materials.

FIG. 23 is a diagram showing a first charge capacity of a battery manufactured using two types of graphite-based carbon materials, and a relation between contact heat between those materials and tertiary butanol.

FIG. 24 is a diagram illustrating a first charge capacity of a battery manufactured using two types of graphite-based carbon materials, and a relationship between contact heat between the materials and benzene.

FIG. 25 is a diagram showing a discharge capacity of a battery manufactured using two types of graphite-based carbon materials, and a relationship between contact heat between those materials and dimethyl sulfoxide.

FIG. 26 is a diagram showing the discharge capacity of batteries manufactured using two types of graphite-based carbon materials and the relationship between the contact heat of those materials and tertiary butanol.

FIG. 27 is a configuration diagram of an apparatus for measuring the amount of heat of contact between a carbon material and various organic solvents according to the method of the present invention to evaluate the carbon material.

FIG. 28 is a flow chart showing a process of measuring the amount of heat of contact between a carbon material and various organic solvents according to the method of the present invention, and evaluating the carbon material.

FIG. 29 is a diagram showing a discharge curve of a battery produced using a non-graphitizable carbon material and a graphite-based carbon material selected by the evaluation method according to the present invention.

FIG. 30 is a diagram showing a discharge curve of a battery manufactured using a graphitizable carbon material selected by the evaluation method according to the present invention.

[Description of Signs] 1 Measuring container for twin calorimeter, 2 reference container for twin calorimeter, 3 thermoelectric bank, 4 amplifier, 5 A / D converter,
6 arithmetic unit, 7 storage device, 8 output device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/02-4/04 H01M 4/58 H01M 10/40

Claims (28)

(57) [Claims] 1. A contact calorie obtained by measuring a contact heat between one type of carbon material selected from a non-graphitizable carbon material, a graphitizable carbon material and a graphite-based carbon material and one or more organic solvents. And / or a correlation between a value calculated from the calculated value and an electrode capacitance characteristic of the carbon material obtained by evaluating a battery manufactured using the carbon material, is determined in advance. A method for evaluating a carbon material for a battery, comprising: measuring a contact heat amount between a test carbon material and the plurality of organic solvents; and evaluating an electrode capacitance characteristic of the test carbon material based on a correlation that has been investigated in advance. . 2. The method according to claim 1, wherein the calculated value is a calorific value ratio, an adsorption amount ratio, and / or an adsorption surface area ratio.
The evaluation method according to claim 1. 3. The method according to claim 2, wherein the electrode capacity characteristic is a first time charge capacity,
3. The evaluation method according to claim 1, wherein the discharge capacity is a first discharge capacity, a capacity loss, and a discharge capacity when charged to a voltage lower than normal. 4. 4. The organic solvent is an organic solvent selected from the group consisting of linear hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, alcohols, ketones, ethers, carbonates, sulfoxides, alkyl cyanides, and pyridine. The evaluation method according to claim 1, wherein: 5. The method according to claim 1, wherein the linear hydrocarbon is hexane or 2%.
The evaluation method according to claim 4, wherein the evaluation method is a dotriacontan / hexane solution. 6. The evaluation method according to claim 4, wherein the cyclic hydrocarbon is cyclohexane. 7. The evaluation method according to claim 4, wherein the aromatic hydrocarbon is benzene. 8. The method according to claim 1, wherein the alcohol is normal butanol,
The evaluation method according to claim 4, wherein the evaluation method is tertiary butanol and / or trifluoroethanol. 9. The evaluation method according to claim 4, wherein the ketone is acetone. 10. The method wherein the ether is dipropyl ether,
The evaluation method according to claim 4, wherein the evaluation method is dibutyl ether or tetrahydrofuran. 11. The evaluation method according to claim 4, wherein the carbonate is propylene carbonate, dimethyl carbonate, methyl ethyl carbonate or diethyl carbonate. 12. The evaluation method according to claim 4, wherein said sulfoxide is dimethyl sulfoxide. 13. The method according to claim 4, wherein said alkyl cyanide is acetonitrile. 14. The organic material is selected from the group consisting of linear hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, alcohols, carbonates, sulfoxides and pyridines. The evaluation method according to any one of claims 1 to 3, wherein 15. The organic solvent is selected from the group consisting of hexane, 2% dotriacontane / hexane solution, cyclohexane, benzene, normal butanol, tertiary butanol, trifluoroethanol, propylene carbonate, dimethyl sulfoxide and pyridine. The evaluation method according to claim 14, wherein the evaluation method is a solvent. 16. The carbon material is a graphitizable carbon material, and the organic solvent is an organic solvent selected from the group consisting of linear hydrocarbons, aromatic hydrocarbons, alcohols, carbonates and pyridines. The evaluation method according to claim 1. 17. The method according to claim 17, wherein the organic solvent is an organic solvent selected from the group consisting of hexane, 2% dotriacontane / hexane solution, benzene, normal butanol, tertiary butanol, trifluoroethanol, propylene carbonate, and pyridine. 17. The evaluation method according to claim 16, wherein the evaluation method is characterized in that: 18. The carbon material is a graphite-based carbon material, and the organic solvent is an organic solvent selected from the group consisting of linear hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, alcohols, carbonates, sulfoxides and pyridines. The evaluation method according to claim 1, wherein: 19. The organic solvent is an organic solvent selected from the group consisting of hexane, 2% dotriacontane / hexane solution, cyclohexane, benzene, normal butanol, tertiary butanol, propylene carbonate, dimethyl sulfoxide and pyridine. 19. The evaluation method according to claim 18, wherein: 20. The heat of contact between a non-graphitizable carbon material and hexane (H), and the carbon material comprising benzene (B), normal butanol (nBt), trifluoroethanol (TFE) and dimethyl sulfoxide (DMSO). B / (B + H), nBt / (nBt + H), which is the calorific ratio or adsorption surface area ratio calculated from the contact heat obtained by measuring the contact heat with the organic solvent selected from the group, TFE / (TFE + H) or DM
The correlation between SO / (DMSO + H) and the first discharge capacity of a battery manufactured using the carbon material was previously investigated, and the specimen was made of a non-graphitizable carbon material and hexane and the organic solvent. The contact calorie is measured to calculate the calorific value ratio or the adsorption surface area ratio, based on the correlation investigated in advance,
A method for evaluating a carbon material for a battery, comprising evaluating a first discharge capacity of a battery manufactured using the subject carbon material. 21. Heat of contact between the graphitizable carbon material and benzene (B), and a 2% dotriacontane / hexane solution (Dc / H), normal butanol (nBt) and tertiary butanol (tBt) ) Is the calorific ratio or adsorption surface area ratio calculated from the contact heat obtained by measuring the contact heat with an organic solvent selected from the group consisting of:
The correlation between // (B + Dc / H), B / (B + nBt) or B / (B + tBt) and the first discharge capacity of the battery manufactured using the carbon material was previously investigated. Every, and the calorimetric ratio or the adsorption surface area ratio is calculated by measuring the contact calorific value of the test graphitizable carbon material with benzene and the organic solvent, and based on the correlation investigated in advance, the test carbon material is measured. A method for evaluating a carbon material for a battery, comprising evaluating a first discharge capacity of a battery manufactured using the same. 22. Graphite-based carbon material and hexane (H)
Heat of contact with the carbon material and benzene (B),
B / (B + H) which is a calorific ratio or an adsorption surface area ratio calculated from a contact calorific value obtained by measuring a contact heat with an organic solvent selected from the group consisting of normal butanol (nBt) and dimethyl sulfoxide (DMSO). , NBt / (nBt + H) or D
The correlation between MSO / (DMSO + H) and the first discharge capacity of the battery manufactured using the carbon material has been investigated in advance,
Then, the calorific value ratio or the adsorption surface area ratio is calculated by measuring the contact calorific value of the test graphite-based carbon material and hexane and the organic solvent, and based on the correlation investigated in advance,
A method for evaluating a carbon material for a battery, comprising evaluating a first discharge capacity of a battery manufactured using the subject carbon material. 23. A calorific ratio or an adsorption surface area ratio calculated from a contact calorie obtained by measuring contact heat between a non-graphitizable carbon material or a graphite-based carbon material and hexane (H) and benzene (B). The correlation between / (B + H) and the first discharge capacity of the battery made using the carbon material was investigated in advance, and the contact calorific value of the test carbon material with hexane and benzene was measured. B / (B + H), which is the calorific value ratio or the adsorption surface area ratio, and evaluates the first discharge capacity of the battery manufactured using the subject carbon material based on the correlation investigated in advance. A method for evaluating a carbon material for a battery, comprising: 24. A graphitizable carbon material and benzene (B) and a 2% dotriacontane / hexane solution (Dc /
H / B / (B + Dc / H), which is the calorific ratio or adsorption surface area ratio calculated from the contact calorific value obtained by measuring the contact heat with H).
The correlation between the first discharge capacity of a battery prepared using the carbon material and the first discharge capacity was examined in advance, and the contact calorific value between the test graphitizable carbon material and benzene and a 2% dotriacontane / hexane solution was determined. B / (B + Dc / H), which is the calorific value ratio or the adsorption surface area ratio, is measured and measured, and the first discharge of the battery manufactured using the subject carbon material is performed based on the correlation investigated in advance. A method for evaluating a carbon material for a battery, comprising evaluating a capacity. 25. An apparatus for the evaluation method according to claim 1, wherein the calorimeter comprises a measuring container and a reference container; and a temperature difference between the measuring container and the reference container. Thermometer that measures the temperature; an amplifier that amplifies the temperature difference signal from the thermoelectric bank; A / D that converts the output signal of the amplifier
Converter; an arithmetic unit that integrates a temperature difference signal received via the converter, converts the signal into a contact calorific value, and compares the contact caloric value and a value calculated therefrom with data for evaluating a carbon material; A storage device for storing data used for calculating the data and data for evaluating the carbon material; and an output device for outputting a result. 26. A method for evaluating a carbon material according to claim 1, wherein a carbon material having a desired electrode capacity characteristic is selected, and the selected carbon material is used for a negative electrode. A method for manufacturing a lithium ion battery, comprising: 27. The evaluation method according to claim 23, wherein the value of B / (B + H), which is the calorific value ratio or the adsorption surface area ratio, is 0.2.
A method for producing a lithium ion battery, comprising: selecting 5 or more test carbon materials; and using the selected carbon materials for a negative electrode. 28. The method according to claim 24, wherein the calorific value ratio or the adsorption surface area ratio, B / (B + Dc / H), is not more than 0.4, and the subject carbon material is sorted out. A method for producing a lithium ion battery, comprising using the carbon material thus obtained for a negative electrode.