JPWO2012002457A1 - Raw material carbon composition for negative electrode material of lithium ion secondary battery - Google Patents

Abstract

Provided is a raw material charcoal composition for a negative electrode material for a lithium ion secondary battery that is useful for achieving excellent high-speed charge / discharge characteristics. A raw coal composition having a true specific gravity of 1.30 or more obtained by coking treatment of a heavy oil composition, wherein the raw coal composition is calcined at a temperature of 1000 to 1500 ° C. in an inert gas atmosphere. The carbide obtained by the following formula (1) RD = −0.75 TH mass% + intercept (1) (In the above formula, RD represents the true specific gravity of the carbide, and TH mass% is the A raw material carbon composition for a negative electrode material for a lithium ion secondary battery satisfying a total hydrogen content (mass%) and an intercept in a range of 2.163 to 2.180.

Description

  The present invention relates to a raw material carbon composition that is a raw material for a negative electrode material of a lithium ion secondary battery.

  Lithium ion secondary batteries are lighter and have superior input / output characteristics compared to conventional secondary batteries such as nickel cadmium batteries, nickel metal hydride batteries, and lead batteries. Is expected as a power source. A carbon material is used as an active material constituting an electrode of a lithium ion secondary battery, and various studies have been made on carbon materials so far to improve the performance of lithium ion secondary batteries (for example, patents). References 1-2).

  Carbon materials used as negative electrode materials for lithium ion secondary batteries are generally roughly classified into graphite and amorphous materials. The graphite-based carbon material has an advantage that the energy density per unit volume is higher than that of the amorphous carbon material. Accordingly, graphite-based carbon materials are generally used as negative electrode materials in lithium ion secondary batteries for mobile phones and notebook computers that are compact but require a large charge / discharge capacity. Graphite has a structure in which hexagonal network surfaces of carbon atoms are regularly stacked, and lithium ion insertion / extraction reaction proceeds at the edge of the hexagonal network surface during charge / discharge.

  In addition, petroleum raw coke (raw coke) has been variously studied as a raw material coal for graphite electrodes and capacitors (see, for example, Non-Patent Document 1 and Patent Document 3). However, it varies greatly depending on the intended use, and is insufficient as a carbon material for a negative electrode of a lithium ion secondary battery.

Japanese Patent No. 3056519 Japanese Patent Publication No. 4-24831 JP 2006-179697 A

Carbon, Vol. 26, no. 1, p49-55, 1988

  When a graphite-based carbon material is used as the negative electrode material of a lithium ion secondary battery, the energy density per unit volume can be increased as described above. There was room for improvement in terms of discharge characteristics. This is presumably because the graphite-based carbon material has high crystallinity, and therefore, when it is used for the negative electrode of a lithium ion secondary battery, the diffusion of lithium ions in the carbon layer is limited.

  Conventionally, the crystallinity of a carbon material has been performed according to the crystallinity regulation by X-ray diffraction, but it does not necessarily indicate the characteristics of the entire raw coal composition bulk. This is in the “Commentary / Carbon Family” written by Michio Inagaki (Agne Jofu Co., Ltd.) “When there is selective orientation of crystallites (almost all carbon materials produce selective orientation) It may be understood from the description that "information about the crystallite may be obtained from X-ray diffraction." For this reason, in the case of petroleum coke or the like, the charge / discharge characteristics at a particularly high speed could not be reproducibly expressed.

  The object of the present invention has been made in view of such circumstances, and provides a raw material carbon composition serving as a carbon material for a lithium ion secondary battery that can express high charge and discharge characteristics at high speed with good reproducibility. There is.

  The present inventors have examined a carbon material having an excellent crystal structure by paying attention to the generation mechanism of the crystal structure. For example, in needle coke, thermal decomposition and polycondensation reaction occur by treating heavy oil at a high temperature to produce liquid crystal spheres called mesophase, which combine to produce large liquid crystals called bulk mesophase as intermediate products. It is manufactured through the process. The inventors of the present invention have conducted extensive studies on the influence of the raw material oil composition and the raw material carbon composition used for the production of the carbon material on the crystal structure.

  Graphite materials such as natural graphite, synthetic graphite, and expanded graphite for lithium ion negative electrode, carbonized mesocarbon microbeads, mesophase pitch carbon fiber, vapor grown carbon fiber, pyrolytic carbon, petroleum coke, pitch coke, and Carbon materials such as needle coke, synthetic graphite materials obtained by subjecting these carbon materials to graphitization, or mixtures thereof have been proposed but have been difficult.

  As a result of intensive studies to solve the above-described problems, the present inventors have selectively used a raw coal composition exhibiting specific properties in a carbonized region (1000 to 1500 ° C.), thereby achieving high speed. It was found that high charge / discharge characteristics are expressed with good reproducibility.

In the present invention, a raw coal composition obtained by coking a heavy oil composition containing two or more kinds of heavy oils has a true specific gravity of 1.30 or more, and the raw coal composition is not used. A carbide obtained by calcination at 1000 to 1500 ° C. in an active gas atmosphere is represented by the following formula (1):
RD = −0.75 TH mass% + intercept (1)
(In the above formula, RD represents the true specific gravity of the carbide, TH mass% represents the total hydrogen content (mass%) of the carbide, and the intercept ranges from 2.163 to 2.180.)
Selecting the composition of the heavy oil composition so that
A method for producing a raw material carbon composition for a negative electrode material for a lithium ion secondary battery comprising at least a step of coking a heavy oil composition having a selected composition.
The present invention also relates to a raw coal composition having a true specific gravity of 1.30 or more obtained by coking a heavy oil composition, wherein the raw coal composition is 1000 to 1500 in an inert gas atmosphere. Carbide obtained by calcination at a temperature of ° C. has the following formula (1)
RD = −0.75 TH mass% + intercept (1)
(In the above formula, RD represents the true specific gravity of the carbide, TH mass% represents the total hydrogen content (mass%) of the carbide, and the intercept ranges from 2.163 to 2.180.)
A raw material charcoal composition for a lithium ion secondary battery negative electrode material satisfying the above is provided.
Furthermore, this invention provides a lithium ion secondary battery provided with the negative electrode material using this raw material charcoal composition.

The effect of crystallinity obtained from the correlation between the specified true specific gravity (RD) and the total hydrogen content (TH mass%) is considered to work in the same way in the raw coke before firing and the subsequent graphitization process. . It was also found that a carbon material having excellent characteristics can be selected by evaluating the crystallinity as a calcined coke even in a graphitized carbon material.
According to the present invention, the crystallinity from RD / TH is measured for the entire bulk of the raw coal composition, and by appropriately adjusting this, high charge / discharge characteristics at high speed can be reproduced with good accuracy. can get.

It is a graph which shows the relationship between true specific gravity (RD) and total hydrogen content (TH mass%).

In the present invention, a raw material charcoal composition having a true specific gravity of 1.30 or more obtained by coking a heavy oil composition is calcined at a temperature of 1000 to 1500 ° C. in an inert gas atmosphere to obtain a carbide. Thus, the relationship between the true specific gravity (RD) of the carbide and the total hydrogen content (TH mass%) is utilized.
The coking process is a process for coking the heavy oil composition, and a delayed coking method is preferred. More specifically, a heavy coal composition is heat-treated with a delayed coker under a pressurized condition to obtain a raw coal composition. The conditions of the delayed coker are preferably a pressure of 300 to 800 kPa and a temperature of 400 to 600 ° C.
The inert gas that is an atmosphere gas when calcining the raw material carbon composition at 1000 to 1500 ° C. is not particularly limited, and an inert gas that is usually used in this field, such as nitrogen or argon, is used. In order to remove oxygen as much as possible, it is desirable to replace the atmospheric gas with an inert gas after reducing the pressure once.

The true specific gravity and the total hydrogen content (TH mass%) are measured by the following methods. However, if the same evaluation is possible, other known methods may be used.
In the present invention, the true specific gravity is measured according to JIS K2151.
The total hydrogen content (TH mass%) is measured by completely burning the calcined sample at 750 ° C. in an oxygen stream, and determining the amount of water generated from the combustion gas by the coulometric titration method (Karl Fischer method). In the coulometric titration Karl Fischer method, an electrolyte containing iodide ions, sulfur dioxide, base (RN) and alcohol as main components is placed in the titration cell in advance, and the sample is placed in the titration cell. Moisture reacts according to formula (2).
H ₂ O + I ₂ + SO ₂ + CH ₃ OH + 3RN
→ 2RN · HI + RN · HSO ₄ CH ₃ (2)
Iodine necessary for this reaction is obtained by electrochemically reacting iodide ions (two-electron reaction) (the following formula (3)).
_{^{2I - + 2e → I 2 (}} 3)
Since 1 mol of water reacts with 1 mol of iodine, the amount of electricity required to titrate 1 mg of water is determined as follows according to Faraday's law.
(2 × 96478) / (18.0153 × 10 ³ ) = 10.71 Coulomb Here, the constant 96478 is the Faraday constant, and 18.0153 is the molecular weight of water.
By measuring the amount of electricity required to generate iodine, the amount of water can be determined.
Furthermore, it converts into the amount of hydrogen from the obtained moisture content, and remove | divides this by the sample mass used for the measurement, and calculates total hydrogen content (TH mass%).

  Conventionally, the crystallinity of raw coal has been evaluated by measuring the distance between layers and the size of crystallites by direct X-ray diffraction, but in the present invention, it is related to the crystallinity characteristics of calcined coke. The correlation between the true specific gravity (RD) of the calcined coke and the total hydrogen content (TH mass%) was found. The relationship between the true specific gravity (RD) of calcined coke and the value of hydrogen content (TH mass%) is as follows: starting oil (desulfurized desulfurized oil, hydrodesulfurized heavy oil, fluidized catalytic cracker residual oil (CLO), etc. ) And the blending ratios thereof were significantly different, and it was found that the crystallinity of the entire bulk could be adjusted by adjusting these.

The raw material carbon composition of the carbon material for negative electrode of the lithium ion secondary battery of the present invention is a raw material carbon composition having a true specific gravity of 1.30 or more obtained by coking treatment of a heavy oil composition, A carbide obtained by calcining the charcoal composition at a temperature of 1000 to 1500 ° C. in an inert gas atmosphere is represented by the following formula (1).
RD = −0.75 TH mass% + intercept (1)
(In the above formula, RD represents the true specific gravity of the carbide, TH mass% represents the total hydrogen content (mass%) of the carbide, and the intercept ranges from 2.163 to 2.180.)
Meet. The characteristics of the carbon material obtained by carbonizing and / or graphitizing this raw material carbon composition ensure an orderly lithium ion diffusion path and suppress physical displacement of the hexagonal mesh plane due to lithium ion diffusion. It has a crystal structure that can be made. The lithium ion diffusion path is a pseudo two-dimensional space formed on adjacent stacked hexagonal planes and a three-dimensional space formed between adjacent crystallites. For this reason, it turned out that the lithium ion secondary battery in which the carbon material made from the raw material charcoal composition of the present invention is used as a negative electrode can realize extremely high charge / discharge characteristics with good reproducibility.

  The true specific gravity of the raw coal obtained by coking the heavy oil composition is suitably 1.30 or more, preferably 1.45 or less, more preferably 1.43 or less. If it is less than 1.30, the basic skeleton formation of carbon in coking is insufficient, and melting and foaming occur in the subsequent carbonization process. For this reason, the crystal structure that becomes an ordered diffusion path of lithium ions imparted in the coking process becomes messy. When such a raw material carbon composition is used, it satisfies the provisions of true specific gravity (RD) and total hydrogen content (TH mass%) of calcined coke, but is obtained by subsequent carbonization and / or graphitization. The obtained negative electrode material does not secure an orderly lithium ion diffusion path and has a low charge / discharge capacity. Further, when the true specific gravity exceeds 1.45, carbonization is further promoted by the coking process, and the generation of cracked gas in the coking process may be rapid. For this reason, the crystal structure of the raw coal becomes messy due to the rapid generation of cracked gas, and even if the subsequent carbonization process is performed, an orderly lithium ion diffusion path may not be formed.

FIG. 1 shows an example of a raw coal composition in which two or more types are selected from the group consisting of desulfurized desulfurized oil, hydrodesulfurized heavy oil, and bottom oil of a fluid catalytic cracker, and the mixing ratio is adjusted. FIG. 1 shows true specific gravity (RD) and total hydrogen content (TH mass%) when four types of raw coal compositions (A, B, C, D) are fired at 1000 to 1500 ° C. in an inert gas atmosphere. ). In FIG. 1, desulfurized desulfurized oil, hydrodesulfurized heavy oil, and bottom oil of a fluid catalytic cracker are used as the heavy oil forming the raw coal compositions A, B, C, D, and the blending ratio is What was changed was used (see Examples 1-4).
As shown in FIG. 1, it can be seen that in any case, the vehicle rides on a straight line having an inclination of -0.75. As shown in Table 1, these multiple correlation coefficients (R) were 0.93 or more and highly reliable.

Further, when an intercept at which TH mass% = 0 is obtained and the value is 2.163 to 2.180, high charge / discharge characteristics at a higher speed than in the prior art can be obtained with good reproducibility.
Here, the true specific gravity (RD) and the total hydrogen content (TH mass%) of the carbide obtained after heating when calcined at 1000 to 1500 ° C. are related to the crystal structure of the carbide, and the intercept Is less than 2.163, the crystal structure is poorly developed, there are many crystal disturbances, and an orderly lithium ion diffusion path is not ensured. Further, a lot of physical energy is required for doping lithium ions on the layer surface of the adjacent carbon hexagonal network surface, and the amount of doped lithium ions is reduced. For these reasons, the battery performance is extremely low and charging characteristics at high speed.
On the other hand, when the intercept exceeds 2.180, the crystal structure is excessively developed, and the growth of crystallites in the a-axis direction becomes extremely large. This is because, at low speed, the layer surface of the carbon hexagonal network surface is doped with a large amount of lithium ions, but on the other hand, the diffusion path of lithium ions is reduced. For this reason, although the conventional low speed output characteristics are excellent, the desired high speed discharge characteristics do not become high.

Except for the raw coal composition shown in FIG. 1, the true specific gravity (RD) and the total hydrogen content (TH mass%) were examined by the same method, but both are on a straight line having a slope of approximately −0.75. It was confirmed that the ride. Examples of other raw coal compositions include bottom oil of a residual fluid fluid catalytic cracker (RFCC), vacuum residue oil (VR), vacuum distillate oil (VD), atmospheric residue, and ethylene tar. The residual oil fluid catalytic cracking unit (RFCC) uses residual oil (normal pressure residual oil, etc.) as a raw material oil and selectively performs a cracking reaction using a catalyst to obtain a high-octane FCC gasoline. Is a fluid catalytic cracking device of the type. As bottom oil of the residual oil fluid catalytic cracker (RFCC), for example, residual oil such as atmospheric residual oil is used in a reactor reaction temperature (ROT) range of 510 to 540 ° C. and a catalyst / oil mass ratio of 6 to 8. A bottom oil produced by changing the range is mentioned. The residual oil (VR) of the vacuum distillation apparatus is obtained by subjecting crude oil to an atmospheric distillation apparatus to obtain gas, light oil, and atmospheric residual oil, and then heating the atmospheric residual oil under a reduced pressure of, for example, 10 to 30 Torr. It is the bottom oil of the vacuum distillation apparatus obtained by changing in the range of the furnace exit temperature 320-360 degreeC. The distillation oil of the vacuum distillation apparatus is the distillation oil of the vacuum distillation apparatus obtained by changing the above atmospheric residual oil, for example, in a range of 320 to 360 ° C. at a furnace outlet temperature under a reduced pressure of 10 to 30 Torr. is there.
Therefore, in order to prepare such a specified raw coal composition, for example, caustic heavy hydrocarbons having appropriate aromaticity and containing as little impurities as possible such as sulfur and metals are coked. Can be obtained.

“Heavy hydrocarbon with moderate aromaticity” means, for example, petroleum-based desulfurized and desulfurized oil, hydrodesulfurized heavy oil, bottom oil of fluid catalytic cracking equipment, vacuum residue (VR), coal liquefaction And oil, coal solvent extraction oil, atmospheric residue oil, shell oil, tar sand bitumen, naphtha tar pitch, coal tar pitch, and heavy oil obtained by hydrorefining these.
Desulfurized desulfurized oil is obtained by, for example, treating oil such as vacuum distillation residue oil with a solvent desulfurization apparatus using propane, butane, pentane, or a mixture thereof as a solvent, and removing the asphaltenes. Desulfurized oil (DAO) is preferably desulfurized to a sulfur content in the range of 0.05 to 0.40 mass%. For example, the hydrodesulfurized oil is obtained by hydrodesulfurizing an atmospheric distillation residue having a sulfur content of 2.0 to 5.0% by mass in the presence of a catalyst so that the hydrocracking rate is 25% or less. 0.1 to 0.6% by mass. The hydrodesulfurization conditions at this time are, for example, a total pressure of 180 MPa, a hydrogen partial pressure of 160 MPa, and a temperature of 380 ° C. Fluid catalytic cracking (FCC) equipment uses fluidized-bed fluid catalytic cracking (FCC) to obtain high-octane FCC gasoline by using reduced pressure gas oil as a feedstock and selectively performing a cracking reaction using a catalyst. ). The vacuum residue (VR) is obtained by subjecting crude oil to an atmospheric distillation apparatus to obtain gas, light oil, and atmospheric residue, and then subjecting the atmospheric residue to, for example, a heating furnace outlet temperature under a reduced pressure of 10 to 30 Torr. It is the bottom oil of the vacuum distillation apparatus obtained by changing in the range of 320-360 degreeC.
When a raw material oil composition is prepared by blending two or more kinds of raw material oils, the raw material composition is obtained by appropriately adjusting the blending ratio according to the properties of the raw material oil to be used.

  If the raw material oil composition according to the present embodiment is used, it becomes possible to produce a carbon material for a negative electrode of a lithium ion secondary battery particularly suitable for high-speed charge / discharge. In addition, the raw oil composition is separated into an aromatic component and a non-aromatic component by elution chromatography, and the composition of the raw oil composition (the content of the aromatic component, the molecular weight of the aromatic component, and the non-aromatic component By analyzing the (normal paraffin content), a raw material oil composition suitable for producing a carbon material for a lithium ion secondary battery negative electrode suitable for high-speed charge / discharge can be efficiently selected.

In the raw material oil composition, the content of the aromatic component in the total mass of 100% by mass is preferably 35 to 80% by mass, and the molecular weight of the aromatic component is 250 to 1600. It is essential for the production and growth of good mesophase as a precursor of raw coke.
The method for measuring the content of the aromatic component is based on the “elution chromatography method”. The “elution chromatography method” means a method for separating a feedstock composition into two components (aromatic component and non-aromatic component) in accordance with the method described in ASTM (American Society for Testing and Materials) D2549. Specifically, 8 g of the raw oil composition dissolved in 20 mL of n-pentane or cyclohexane is passed through a column packed with activated alumina and silica gel. Thereafter, 130 mL of n-pentane is passed through the column at a rate of 3 mL / min to elute non-aromatic components into n-pentane. Non-aromatic components eluted in n-pentane are collected and quantified. Thereafter, 100 mL of diethyl ether, 100 mL of chloroform, and 175 mL of ethyl alcohol, which are solvents, are sequentially passed through the column at a rate of 3 mL / min to elute the aromatic components in the solvent. Aromatic components eluted in the solvent are collected and quantified.
Moreover, content of the aromatic component and non-aromatic component with respect to the total mass of a raw material oil composition means the value calculated by following formula (1) and (2), respectively. In the formula, A and B respectively indicate the masses of the aromatic component and the non-aromatic component obtained by the separation treatment by the elution chromatography method.
Aromatic component content (% by mass) = A / (A + B) × 100 (1)
Content of non-aromatic component (% by mass) = B / (A + B) × 100 (2)
The average molecular weight of the feed oil composition is measured by a vapor pressure equilibrium method. The outline of the vapor pressure equilibrium method is as follows. Two thermistors are placed in a saturated vapor of a solvent maintained at a predetermined temperature, and the sample solution is dropped on one side and the solvent alone is dropped on the other side. At this time, since the vapor pressure of the sample solution is lower than that of the solvent alone, the vapor in the atmosphere around the thermistor condenses on the sample solution. Since the temperature rises due to the latent heat released at this time, this temperature difference is obtained as the voltage difference (ΔV) of the thermistor, and the relationship between the molar concentration and the voltage difference (ΔV) is obtained using a standard sample whose molecular weight is known in advance. From the calibration curve, the sample molar concentration in the sample solution is obtained, and the average molecular weight is calculated. In the present invention, cyclohexane is used as a solvent, and n-cetane (molecular weight: 226.4) is used as a standard sample.
For example, a raw material oil composition that deviates from this is coke-formed before it grows, and a coke having a small structure called a mosaic is obtained. Such coke does not develop a carbon layer surface even after carbonitizing graphite, and the edge surface with high reactivity becomes extremely large. If such a material is used for the negative electrode, gas is generated due to a reaction between the electrolytic solution and the carbon edge surface, which is not preferable.

The normal paraffin contained in the raw material oil composition is effective for orienting crystals in the uniaxial direction when the mesophase is solidified in the coke production process. The content of normal paraffin in the total mass of 100% by mass of the raw material oil composition is preferably 3% by mass or more, and if the content of normal paraffin exceeds 45% by mass, excessive gas generation from normal paraffin results in bulk. There is a tendency to work in the direction that disturbs the orientation of the mesophase. In this case, even in the carbonization graphitization process, the alignment of the carbon layer surface is poor, so that a large amount of lithium ions cannot be taken in at the time of charging, and the charge / discharge capacity becomes small, which is not preferable.
The method for measuring the normal paraffin content is based on a gas chromatogram equipped with a capillary column. Specifically, after testing with a normal paraffin standard substance, the sample of the non-aromatic component separated by the elution chromatography method is passed through a capillary column and measured. The content based on the total mass of the raw material oil composition is calculated from this measured value.

  The raw material oil composition according to the present embodiment is coked to obtain a raw material charcoal composition, and then heat-treated and artificially graphitized as necessary, as a carbon material for a negative electrode of a lithium ion secondary battery. used. A delayed coking method is preferred as a method for coking a raw oil composition that satisfies a predetermined condition. More specifically, the raw material oil composition is heat-treated with a delayed coker under a pressurized condition to obtain a raw material charcoal composition. The conditions of the delayed coker are preferably a pressure of 300 to 800 kPa and a temperature of 400 to 600 ° C. The carbonization graphitization conditions are not particularly limited, but raw coke is calcined at 1000-1500 ° C. in a rotary kiln, shaft furnace or the like to obtain calcined coke, and then the calcined coke is heated at 2250-2800 ° C. in an Atchison furnace or the like. Graphitize.

  In the present invention, the above-mentioned feedstock composition can be obtained by optimizing the type of starting feedstock and the blend ratio thereof, and these can be caulked under appropriate conditions to obtain a feedstock composition having a specified intercept range. can get.

  Such heavy hydrocarbons are easily graphitizable, and in the coking process, a condensed polycyclic aromatic produced by a thermal decomposition reaction is laminated to form raw carbon containing graphite-like microcrystalline carbon. It becomes. Therefore, as described above, the raw coal obtained from such heavy hydrocarbons also has high graphitization properties. Particularly in the present invention, it is preferable that the graphite-like microcrystalline carbon is contained in the raw material carbon composition.

  Next, a method for producing a negative electrode for a lithium ion secondary battery using a carbonaceous material from the raw material carbon composition obtained from the raw material oil composition, and a lithium ion secondary battery will be described.

  The method for producing a negative electrode for a lithium ion secondary battery is not particularly limited, and examples thereof include a method of pressure-molding a mixture containing a carbon material, a binder, and optionally a conductive additive and an organic solvent according to the present embodiment. It is done. As another method, there is a method in which a carbon material, a binder, a conductive auxiliary agent and the like are slurried in an organic solvent, and the slurry is applied on a current collector and then dried.

  Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, and SBR (styrene-butadiene rubber). The amount of the binder used is appropriately 1 to 30 parts by mass with respect to 100 parts by mass of the carbon material, but is preferably about 3 to 20 parts by mass.

  Examples of the conductive assistant include carbon black, graphite, acetylene black, conductive indium-tin oxide, or conductive polymers such as polyaniline, polythiophene, and polyphenylene vinylene. As for the usage-amount of a conductive support agent, 1-15 mass parts is preferable with respect to 100 mass parts of carbon materials.

  Examples of the organic solvent include dimethylformamide, N-methylpyrrolidone, isopropanol, toluene and the like.

  Examples of the method of mixing the carbon material, the binder, and, if necessary, the conductive additive and the organic solvent include a method using a known apparatus such as a screw kneader, a ribbon mixer, a universal mixer, or a planetary mixer. The obtained mixture is molded by roll pressurization and press pressurization. The pressure at this time is preferably about 100 to 300 MPa.

  There are no particular limitations on the material and shape of the current collector, and for example, a strip-shaped material made of aluminum, copper, nickel, titanium, stainless steel, or the like in the form of a foil, a punched foil, or a mesh may be used. . Further, a porous material such as porous metal (foamed metal) or carbon paper can be used as the current collector.

  The method of applying the negative electrode material slurry to the current collector is not particularly limited. For example, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method. Or well-known methods, such as a screen printing method, are mentioned. After the application, a rolling process using a flat plate press, a calendar roll or the like is performed as necessary.

  Further, the integration of the slurry formed into a sheet shape, a pellet shape or the like and the current collector can be performed by a known method such as a roll, a press, or a combination thereof.

  The lithium ion secondary battery according to the present embodiment is obtained, for example, by disposing a negative electrode for a lithium ion secondary battery and a positive electrode that are manufactured as described above, with a separator interposed therebetween, and injecting an electrolytic solution. be able to.

The active material used for the positive electrode is not particularly limited. For example, a metal compound, metal oxide, metal sulfide, or conductive polymer material that can be doped or intercalated with lithium ions may be used. Lithium oxide (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and their double oxides (LiCo _X Ni _Y Mn _Z O ₂ , X + Y + Z = 1), lithium manganese spinel (LiMn ₂₎ O ₄ ), lithium vanadium compound, V ₂ O ₅ , V ₆ O ₁₃ , VO ₂ , MnO ₂ , TiO ₂ , MoV ₂ O ₈ , TiS ₂ , V ₂ S ₅ , VS ₂ , MoS ₂ , MoS ₃ , Cr ₃ O ₈ , Cr ₂ O ₅ , olivine type LiMPO ₄ (M: Co, Ni, Mn, Fe), poly Examples thereof include conductive polymers such as acetylene, polyaniline, polypyrrole, polythiophene, and polyacene, porous carbon, and the like, and mixtures thereof.

  As the separator, for example, a non-woven fabric, cloth, microporous film, or a combination thereof having a polyolefin as a main component such as polyethylene or polypropylene can be used. In addition, when it is set as the structure where the positive electrode and negative electrode of the lithium ion secondary battery to produce are not in direct contact, it is not necessary to use a separator.

  As an electrolytic solution and an electrolyte used for the lithium secondary battery, known organic electrolytic solutions, inorganic solid electrolytes, and polymer solid electrolytes can be used. Preferably, an organic electrolyte is preferable from the viewpoint of electrical conductivity.

  Examples of the organic electrolyte include dibutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and ethylene glycol phenyl ether; N-methylformamide, N, N-dimethylformamide, N -Amides such as ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide; sulfur-containing compounds such as dimethylsulfoxide and sulfolane; methyl ethyl ketone; Dialkyl ketones such as methyl isobutyl ketone; cyclic ethers such as tetrahydrofuran and 2-methoxytetrahydrofuran; ethylene carbonate , Butylene carbonate, diethyl carbonate, dimethyl carbonate, methylethyl carbonate, propylene carbonate, carbonates such as vinylene carbonate; include acetonitrile, the organic solvent of nitromethane; .gamma.-butyrolactone; N- methylpyrrolidone. Among these, preferred examples include ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, vinylene carbonate, γ-butyrolactone, diethoxyethane, dimethyl sulfoxide, acetonitrile, tetrahydrofuran, and the like. Preferable examples include carbonate-based non-aqueous solvents such as ethylene carbonate and propylene carbonate. These solvents can be used alone or in admixture of two or more.

Lithium salts are used as solutes (electrolytes) for these solvents. Examples of the lithium salt include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCl, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , and LiN (CF ₃ SO ₂ ) ₂ .

  Examples of the polymer solid electrolyte include a polyethylene oxide derivative and a polymer containing the derivative, a polypropylene oxide derivative and a polymer containing the derivative, a phosphate ester polymer, a polycarbonate derivative and a polymer containing the derivative.

  There are no restrictions on the selection of members other than those described above necessary for the battery configuration.

  The structure of the lithium ion secondary battery using the carbon material according to the present embodiment as a negative electrode material is not particularly limited. Usually, a positive electrode and a negative electrode, and a separator provided as necessary, are wound in a flat spiral shape. In general, a wound electrode plate group is formed, or these are laminated in a flat plate shape to form a laminated electrode plate group, and these electrode plate groups are enclosed in an exterior body. Lithium ion secondary batteries are used as, for example, paper-type batteries, button-type batteries, coin-type batteries, stacked batteries, cylindrical batteries, and the like.

  The lithium ion secondary battery using the carbon material for the negative electrode of the lithium ion secondary battery according to the present embodiment is superior in high-speed charge / discharge characteristics as compared with a lithium ion secondary battery using a conventional carbon material, and is used for automobiles. For example, it can be used for hybrid vehicles, plug-in hybrid vehicles, and electric vehicles.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.
(Examples 1-4 and Comparative Examples 1-6)
(1) Preparation of raw material charcoal composition Various heavy oils are blended to prepare eight types of raw material oil compositions. More specifically, the raw material oil compositions of Examples 1 to 4 are petroleum heavy The raw oil composition was prepared by mixing the desulfurized dewaxed oil and the bottom oil of the hydrodesulfurized heavy oil fluid catalytic cracker at different blend ratios. This raw material oil composition was caulked in an autoclave under a pressure of 0.8 MPa at a temperature of 530 ° C. for 3 hours to obtain a raw material charcoal composition.
The raw material oil composition of Example 1 is 50% by volume of desulfurized dewaxed oil, 30% by volume of hydrodesulfurized heavy oil, 20% by volume of bottom oil of a fluid catalytic cracker, and Example 2 is 50% of desulfurized dewaxed oil. Volume%, hydrodesulfurized heavy oil 20 volume%, bottom oil of fluid catalytic cracker 30 volume%, Example 3 is desulfurized desulfurized oil 50 volume%, hydrodesulfurized heavy oil 10 volume%, fluid contact The bottom oil of the cracker was adjusted to 40% by volume, Example 4 was adjusted to 50% by volume of desulfurized and desulfurized oil, 40% by volume of hydrodesulfurized heavy oil, and 10% by volume of the bottom oil of the fluid catalytic cracker.

In Comparative Example 1, the same raw material composition as in Example 1 was used, and this raw material oil composition was caulked at 480 ° C. for 2 hours in an autoclave under 0.8 MPa pressure to obtain a raw material carbon composition. In Comparative Example 2, the same raw material composition as in Example 2 was used, and this raw material oil composition was caulked at 490 ° C. for 2 hours in an autoclave under a pressure of 0.8 MPa to obtain a raw material carbon composition.
The raw material oil compositions of Comparative Examples 3 to 6 were prepared by mixing with naphthatar, petroleum heavy distillate oil, and high sulfur reduced pressure residue oil, changing the blend ratio, and coking under the same conditions as in the examples. The raw material charcoal composition was obtained. The raw material oil composition of Comparative Example 3 is 50% by volume of naphthatar, 10% by volume of Southern decompression distillate, 40% by volume of Middle Eastern decompression residual oil, and Comparative Example 4 is 30% by volume of naphthatar, Southern decompression distillation. 20% by volume of oil output, 50% by volume of Middle Eastern decompression residue oil, Comparative Example 5 is 10% by volume of naphthatar, 10% by volume of Southern decompression residue oil, 80% by volume of Middle Eastern decompression residue oil, Comparative Example No. 6 was adjusted to 20% by volume of the southern decompression distillate oil and 80% by volume of the Middle Eastern decompression residue oil.

  Each raw carbon composition (raw coke) was calcined at 1000 ° C. for 1 hour to obtain calcined coke. Further, the calcined coke was graphitized at 2400 ° C. for 5 minutes to obtain a carbon material for a negative electrode of a lithium ion secondary battery.

(2) Evaluation of charge / discharge of negative electrode material (a) Production of negative electrode 80 microparticles of carbon material for lithium ion secondary battery negative electrode as active material, acetylene black (AB) as conductive material, and polyvinylidene fluoride (PVDF) as binder: 80: A slurry was prepared by mixing in N-methyl-2-pyrrolidone at a ratio of 10:10 (mass ratio). The slurry was applied on a copper foil, dried on a hot plate for 10 minutes, and then press-molded with a roll press.
(B) Production of battery for evaluation The above composition (30 × 50 mm) as the negative electrode, lithium nickelate (30 × 50 mm) as the positive electrode, ethylene carbonate (EC) / methyl ethyl carbonate (MEC) mixed solution (EC / MEC mass ratio: 3/7, solute: LiPF ₆ (1 M molar concentration), and a polyethylene microporous membrane was used as a separator.
(C) Evaluation of high-speed charge / discharge rate characteristics Table 3 shows the measurement results of the high-speed charge / discharge characteristics of the battery prepared. The C rate in this evaluation was 10C. Utilization% was determined by dividing the charge / discharge capacity at 10C by the charge / discharge capacity at 1C.

The true specific gravity (RD) of the raw coal composition according to Examples 1 to 4 is 1.30 or more, and the true specific gravity (RD) and total hydrogen of the carbide obtained after heating when calcined at a temperature of 1000 to 1500 ° C. The content (TH mass%) is the following formula (1)
RD = −0.75 TH mass% + intercept (1)
The intercept at this time satisfies the condition of 2.163 to 2.180 (see FIG. 1 and Tables 1 and 2).

As shown in Table 3, the lithium ion secondary battery using the carbon material manufactured from the raw material carbon composition according to Examples 1 to 4 as the negative electrode is manufactured from the raw material carbon composition according to Comparative Examples 1 to 6. Compared with the carbon material used for the negative electrode, both the charge capacity and discharge capacity under high-speed charge / discharge conditions (10C) were excellent in a well-balanced manner.
The true specific gravity (RD) of the raw material coal compositions of Comparative Examples 1 and 2 is as low as less than 1.30, which satisfies the above-mentioned conditions for the intercept. Became messy, and the charge / discharge characteristics at high speed were inferior.
Although the true specific gravity (RD) of the raw coal composition according to Comparative Examples 3 to 6 was 1.30 or more, the above-mentioned defined intercept did not satisfy the conditions of 2.163 to 2.180.

Claims (4)

A raw coal composition obtained by coking a heavy oil composition containing two or more heavy oils has a true specific gravity of 1.30 or more, and the raw coal composition is subjected to an inert gas atmosphere. The carbide obtained by calcining at a temperature of 1000 to 1500 ° C. is represented by the following formula (1)
RD = −0.75 TH mass% + intercept (1)
(In the above formula, RD represents the true specific gravity of the carbide, TH mass% represents the total hydrogen content (mass%) of the carbide, and the intercept ranges from 2.163 to 2.180.)
Selecting the composition of the heavy oil composition so that
A method for producing a raw material carbon composition for a negative electrode material for a lithium ion secondary battery comprising at least a step of coking a heavy oil composition having a selected composition.   The step of selecting the composition of the heavy oil composition selects at least two types from the group consisting of desulfurized desulfurized oil, hydrodesulfurized heavy oil, and bottom oil of a fluid catalytic cracker, and adjusts the mixing ratio. The manufacturing method of the raw material carbon | charcoal composition for lithium ion secondary battery negative electrode materials of Claim 1 including doing. A raw coal composition having a true specific gravity of 1.30 or more obtained by coking treatment of a heavy oil composition, wherein the raw coal composition is calcined at a temperature of 1000 to 1500 ° C. in an inert gas atmosphere. The carbide obtained by the following formula (1)
RD = −0.75 TH mass% + intercept (1)
(In the above formula, RD represents the true specific gravity of the carbide, TH mass% represents the total hydrogen content (mass%) of the carbide, and the intercept ranges from 2.163 to 2.180.)
A raw material carbon composition for a lithium ion secondary battery negative electrode material satisfying   A lithium ion secondary battery comprising a negative electrode material using the raw material carbon composition according to claim 3.

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