JPH11343108A - Preparation of cathode material for lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cathode material having low reactivity with an electrolytic solution and an excellent electric discharge characteristic by adding an org. solvent to a separated carbon core material and washing, drying and calcining, after immersing the carbon core material in a carbon material for coating film formation. SOLUTION: Washing of a carbon core material with an org. solvent is preferably carried out at 10-300 deg.C, after immersing the carbon core material in a coating film forming carbon material at 10-300 deg.C. The coating film forming carbon material is a coal and/or petroleum heavy oil, suitably a tar and/or a pitch, which is preferably made to have primary QI of <=3% by removing previously at least a part of the primary QI. The org. solvent for washing is selected from toluene, quinoline, acetone or the like, a coal oil and a petroleum oil. Coating ratio (c) of the coating film forming carbon material/(core material + the coating film forming material) is preferably 0<c<=0.3. Spherical particles of which the corner becomes round are obtained without pulverizing because inter particle fusion and aggregation do not occur even if carrying out washing, drying and calcining.

Description

DETAILED DESCRIPTION OF THE INVENTION technical content field The present invention relates to a method and its manufacturing a carbon material, particularly surface carbon powder coated with components such as heavy oil and relates its production process,
More specifically, the present invention relates to a carbon material useful as an isotropic graphite material, a negative electrode material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery using such a carbon material.

[0001] Background technology in recent years electronic devices, portable devices such as information devices are becoming progress (hereinafter referred to as "portable devices") compact and lightweight is remarkable, is very secondary battery to drive them It is becoming an important part. Lithium secondary batteries are lightweight and have high energy densities, so they are promising as power sources for driving portable devices, and research and development are being actively promoted. However, when lithium metal is used for the negative electrode, repetition of charge / discharge cycles generates and grows dendrite on lithium metal, causing an internal short circuit, making it difficult to form a secondary battery. The use of a lithium alloy such as a lithium-aluminum alloy instead of lithium metal has been proposed. However, in this case, when a charge / discharge cycle or deep charge / discharge is performed, segregation of the alloy occurs, so that a long term However, sufficient characteristics cannot be obtained.

Therefore, a battery using a negative electrode utilizing a carbon material as a host material and utilizing lithium ion insertion / desorption reaction has been proposed, researched and developed, and put to practical use. A lithium secondary battery using a carbon material for a negative electrode is excellent in cycle characteristics, safety, and the like.

However, carbon materials have a wide range of structures and forms from graphite to amorphous carbon, and their physical properties or the fine structure formed by the hexagonal mesh of carbon greatly affect the performance of the electrode. Various carbon materials having specified values or microstructures have been proposed.

The currently used negative electrode materials for lithium secondary batteries are roughly classified into carbon-based materials fired at about 1000 ° C. and graphite-based materials fired at about 2800 ° C. When the former is used as a negative electrode of a lithium secondary battery,
It has the advantage that the reaction with the electrolytic solution is small and the decomposition of the electrolytic solution is unlikely to occur, but it has the disadvantage that the change in potential due to the release of lithium ions is large. On the other hand, the latter has an advantage that when used as a negative electrode of a lithium secondary battery, the change in potential accompanying the release of lithium ions is small, but the latter reacts with the electrolytic solution to cause decomposition of the electrolytic solution. The disadvantage is that the carbon material is destroyed (J. Electro
chem. Soc. 117, 222 (1970)). As a result, in the latter,
Problems such as a decrease in charge / discharge efficiency, a decrease in cycle characteristics, and a decrease in battery safety occur. It has been reported that a graphite-based material can be used when a specific electrolyte is used (J. Electrochem. Soc. 137, 2009 (1990)). Is problematic in that the improvement in battery temperature characteristics, cycle characteristics and the like is considerably limited by the type of electrolyte.

In order to solve this problem, Japanese Patent Application Laid-Open Nos. 4-368778, 4-370662, 5-94838,
Japanese Patent Application Laid-Open No. 5-121066 proposes a carbon material in which the surface of graphite particles is coated with low-crystalline carbon. Since these surface-modified carbon materials suppress the decomposition of the electrolytic solution, they are effective for increasing the battery capacity, improving the cycle characteristics, and the like.

However, according to the technique described in Japanese Patent Application Laid-Open No. 4-368778, since the carbon coating layer is formed on the surface of the carbon particles by a vapor phase method, fusion and aggregation of the carbon particles do not occur. Materials with excellent performance can be obtained, but cost,
There is a serious problem in terms of mass productivity and the like.

[0007] JP-A-4-370662, JP-A-5-94838, and JP-A-5-121066 disclose a method utilizing liquid-phase carbonization which is promising in terms of cost and mass productivity. ing. However, simply mixing and firing a liquid phase organic compound and graphite particles causes the graphite particles to fuse and agglomerate during carbonization, so it is necessary to pulverize the material during electrode fabrication, The pulverization causes problems such as newly exposing an active surface of graphite, mixing of impurities during the pulverization, and complicating the process.

[0008] onset Ming disclosures present invention has no selectivity or restrictions on the electrolyte, and by making a negative electrode for use potential change is small carbon materials of lithium ions, cycle, safety The main object is to obtain a lithium secondary battery having excellent characteristics such as the above.

The present inventor has conducted intensive studies in order to eliminate or reduce the problems of the prior art as described above. As a result, the present inventors have found that a particulate carbon material as a core material (hereinafter referred to as a "core carbon material" to a "core carbon material"). "Carbon material to be used as material" or simply "core material") is used as a raw material for coating-forming carbon material (for example, coal-based heavy oil such as tar or pitch or petroleum-based heavy oil; Oil, etc.), and when separating it from heavy oil, etc., if a specific means is adopted, manufacture a carbon material whose core material surface is uniformly covered with pitch. I found that I got it. The carbon material particles having a two-layer structure obtained in this manner have a spherical or ellipsoidal shape or a shape similar thereto, and have a shape in which the edge portion of the carbon crystal is rounded. There was found.
Furthermore, as a result of the measurement by the BET method, the value of the specific surface area of the particles is smaller than that of the core carbon material before the treatment,
It was also revealed that pores related to the specific surface area by the BET method were blocked in some way.

According to the present invention, the carbon material serving as the core material is
From heavy oil, etc. on part of or the entire base surface
Carbon material adheres or edges and basal plane
Is partially or entirely coated with the carbon material,
A particulate coating having a substantially spherical or elliptical shape;
A coated carbon material is provided. In this carbon material, BE
The pores involved in the specific surface area measured by the T method are heavy
Blocked by adhesion or coating of carbon derived from oil etc.
And the specific surface area is 5m^Two/ g or less (preferably 1 to 5 m ^Two/ g
Degree).

In the present invention, as a carbon material serving as a core material, an average spacing (d) of (002) planes by X-ray wide-angle diffraction method is used.
(002) is 0.335 to 0.340 nm, the crystallite thickness (Lc) in the (002) plane direction is 10 nm or more (more preferably, 40 nm or more), and (11)
0) A highly crystalline graphite material having a crystallite thickness (La) in the plane direction of 10 nm or more (more preferably, 50 nm or more) is used.

In the carbon material according to the present invention, the carbon material which adheres to the core material surface or coats the core material surface (hereinafter also referred to as a carbon material for forming a coating), compared with the crystallinity of the core material described above. Is characterized by low crystallinity.

The value of the true specific gravity of the carbon material according to the present invention is in the range of 1.50 to 2.26 g / cm ³ .

When such a carbon material is employed as a negative electrode material of a lithium secondary battery, a lithium secondary battery having high capacity and high safety can be obtained.

The coated carbon material as described above according to the present invention comprises:
It is manufactured as follows. First, a carbon material serving as a core material is immersed in coal or petroleum heavy oil such as tar or pitch, preferably at about 10 to 300 ° C., and coated with heavy oil or the like. After separating the material from heavy oil, etc., add an organic solvent to the separated coated carbon material,
Preferably, after washing at about 10 to 300 ° C, drying is performed.

Further, the present invention provides a method for producing a carbon material by carbonizing and firing the coated carbon material coated with the heavy oil obtained as described above, and the heavy oil obtained as described above. The present invention also provides a method for producing a carbon material by graphitizing and firing the coated carbon material coated with the carbon material.

In the present invention, in the carbon material obtained by the above-described production method, particles having a particle size of 1 μm or less as measured by a laser diffraction type particle size distribution are set to be 10% or less of the total volume-based integrated value. Is preferred.

Further, in the present invention, as the heavy oil for immersing the carbon material, at least a part of the primary QI is removed and the remaining primary QI is reduced to 3% or less (preferably 1% or less). It is preferable to use

Further, the present invention provides a negative electrode material for a lithium secondary battery comprising the above-mentioned carbonized or graphitized carbon material as a constituent element, a negative electrode for a lithium secondary battery using the negative electrode material, Provide a non-aqueous lithium secondary battery and a solid electrolyte secondary battery using the negative electrode.

In the present invention, the “substantially spherical or ellipsoidal” carbon material is defined as
Although the shape of the carbon material particles as the core material is inherited, the carbon components derived from heavy oil etc. adhere to all or a part of the edges and the basal plane of the carbon material as the core material, and the corners are eliminated. It also includes carbon materials in various states. Such a carbon material is efficiently produced by the production method of the present invention which does not include a pulverizing step after coating and firing,
In the present invention, which is not limited to the material produced by the present production method, the `` pores involved in the specific surface area measured by the BET method, the raw material for coating-forming carbon material, that is, such as tar and pitch A carbon material derived from coal-based or petroleum-based heavy oil adheres or is covered by such a carbon material, and is blocked. "A carbon material has a specific surface area measured by the BET method. This includes a state in which the involved pores are at least partially blocked by a fired product of the carbon material for forming the coating (this is referred to as the carbon material for forming the coating). That is, the pores need not be completely filled with a carbon material derived from heavy oil, etc., for example,
It also includes a carbon material having pores in which the carbon material adheres only near the entrance of the pore and the entrance is closed. Such a state is confirmed by the fact that the specific surface area is small when the specific surface area is measured by the BET method.

In the carbon material obtained by the present invention, a low crystalline carbon material + a low crystalline carbon material; a low crystalline carbon material + a high crystalline carbon material; a high crystalline carbon material + a low crystalline carbon material; Four combinations of a crystalline carbon material and a highly crystalline carbon material are possible, and in all cases, an effect of reducing decomposition of the electrolytic solution and the like can be obtained.

In the present invention, low-crystalline carbon refers to a treatment required for graphitization (for example, high-temperature treatment)
Carbon that cannot be made into graphite crystals even if the above method is used, and such carbon is usually called hard carbon. The term “highly crystalline carbon” means “carbon that becomes a graphite crystal by being treated to be graphitized”, and such carbon is usually called soft carbon.

In the present invention, an outer carbon material ("carbon material for forming a coating", "carbon material for surface modification") derived from a core material and heavy oil adhering to or coating the core material. , "Coating material", etc.) and adjustment of the final baking temperature, a carbon material having the following eight configurations can be obtained. A carbon material in which the carbonized core material is made of a low-crystalline carbon material and the carbon material for forming the coating is made of a low-crystalline carbon material; the carbonized core material is made of a low-crystalline carbon material A carbon material whose coating-forming carbon material is made of a high-crystalline carbon material; a carbon material that has been graphitized and whose core material is made of a low-crystalline carbon material and whose coating-forming carbon material is made of a low-crystalline carbon material; A carbon material in which the treated core material is made of a low-crystalline carbon material and the carbon material for forming the coating is made of a high-crystalline carbon material; A carbon material whose material is made of a low crystalline carbon material; a carbon material that has been carbonized, a carbon material whose core material is made of a high crystalline carbon material, and a carbon material for forming a coating that is made of a high crystalline carbon material; The core material is made of highly crystalline carbon material A carbon material in which the coating-forming carbon material is made of a low-crystalline carbon material; and a graphitized carbon material in which the core material is made of a high-crystalline carbon material and the coating-forming carbon material is made of a high-crystalline carbon material. is there.

According to the present invention, by coating the core material with the exterior carbon material, a carbon material for a secondary battery having a small specific surface area and excellent charge / discharge properties can be efficiently obtained. In particular, according to the combination of the core material and the coating material shown in the above and the above, a carbon material for a battery having remarkably excellent charge / discharge properties is obtained, and, and According to the combination, the specific surface area is small,
A carbon material for a battery that can improve the safety of the battery is obtained.

In the present invention, the carbon material serving as the core material may be natural graphite, artificial graphite, mesocarbon microbeads, mesophase pitch, etc. in the form of particles (flaky to massive, fibrous, whisker-like, spherical, crushed, etc.). One or more of powder, isotropic pitch powder, resin charcoal, and their respective carbonized and graphitized products can be used. Among these, scaly or massive natural graphite and artificial graphite are:
Since it is very cheap, it is preferable in terms of cost. In addition, since carbonized and graphitized products of mesocarbon microbeads (MCMB) are materials having a very small specific surface area, when used as a core material, a material having a smaller specific surface area can be obtained. This is preferable from the viewpoint of safety of the secondary battery.

As the carbon material as the core material, more preferably, the average interplanar spacing (d00) of the (002) plane by X-ray wide-angle diffraction method is used.
2) is 0.335 to 0.340 nm, and the crystallite thickness (Lc) in the (002) plane direction is 1
0 nm or more (more preferably, 40 nm or more), the crystallite thickness (La) in the (110) plane direction is 10 nm or more (more preferably, 50 nm or more), and the peak intensity ratio of 1360 cm- ¹ around 1580 cm ^-1 by argon laser Raman. The peak intensity ratio near the ^-1 (hereinafter referred to as R value) is preferably 0.5 or less (more preferably, 0.4 or less). If the average plane spacing is greater than 0.340 nm, or if Lc, La is less than 10 nm, or if the R value exceeds 0.5, the crystallinity of the carbon material is not sufficient, and when producing a coated carbon material, Low potential near lithium dissolution precipitation (0 to 300 mV based on Li potential)
This is not preferable because the capacity of the device becomes insufficient.

The particle size distribution of the carbon material as the core material is 0.1 to 1
It is preferably about 50 μm. The particle size of the final product containing the carbon material for coating formation derived from heavy oil and the like substantially depends on the particle size of the carbon material as the core material. The particle size will also be approximately defined. When the particle size of the core material is smaller than 0.1 μm,
While the risk of causing an internal short circuit through the pores of the battery separator increases, if it is larger than 150 μm, the uniformity of the electrode, the packing density of the active material, and the ease of handling in the process of manufacturing the electrode Are not preferred.

The weight ratio of the carbon material for forming the coating derived from the heavy oil, that is, the carbon material for forming the coating / (the carbon material for the core material + the carbon material for forming the coating) (hereinafter, this ratio is referred to as the “coating ratio”) Is preferably larger than 0 and 0.3 or less, more preferably 0.01 to 0.2. In this case, the thickness of the coated carbon is in the range of about 0.01 to 10 μm,
A more preferred film thickness is about 0.05 to 5 μm.

When the covering ratio exceeds 0.3, the capacity in the low potential portion derived from the core material decreases, so that it becomes difficult to obtain a sufficient capacity when a battery is manufactured. The amount of the coated carbon referred to here is determined by performing a solvent analysis on the carbon component derived from heavy oil or the like covering the periphery of the core material before firing,
This is a value obtained by measuring the amount of quinoline-soluble components. The thickness of the carbon material for forming the coating is measured by a laser diffraction type particle size distribution analyzer using a central particle size (D50) of the carbon material before coating as a core material and a central particle size of the pitch component-coated carbon material before firing ( D50), and assuming that the carbon material is spherical and the shape of the coating layer of the pitch component is maintained after firing, ｛(particle size after coating)-(particle size of raw material before coating) This value is calculated as (diameter)｝ / 2.

In the present invention, a combination in which the carbon material for forming the coating on the surface has lower crystallinity than the carbon material of the core material is preferable. Further, the average plane spacing (d002) of the (002) plane by the wide angle X-ray diffraction method is 0.335 to 0.340 nm, and the crystallite thickness (Lc) in the (002) plane direction is 10 nm or more (more preferably, 40 nm).
Above), the crystallite thickness (La) in the (110) plane direction is 10 nm or more (more preferably, 50 nm or more), and the R value by argon laser Raman spectroscopy is 0.5 or more (more preferably, 0.
About 5 to 1.5). Plane spacing and R value are indicators of the general crystallinity of graphite.However, due to the nature of these measurement methods, physical properties are reflected in bulk by X-ray diffraction, whereas Raman spectroscopy Reflects the physical properties of the material surface. In other words, a material that satisfies the above physical property values is a highly crystalline material as a bulk property,
The surface means low crystalline. Material after firing R
When the value is smaller than 0.5, the selectivity of the solvent is not completely lost because the crystallinity of the surface is high. In addition, the average plane spacing (d002), which is a property of bulk, is 0.335 to 0.340.
If the deviation is out of the nm range, occlusion of lithium ions
The change in the potential due to the release is large, which is not preferable.

The true density of the coated carbon material having the two-layer structure is about 1.50 to 2.26 g / cm ³ , preferably 1.8 to 2.26 g / cm ^3.
cm ³ , more preferably about 2.0 to 2.26 g / cm ³ .
When making electrodes using materials with low true density,
Since the active material density in the electrode cannot be increased, it is difficult to obtain a high-capacity battery even with a material having excellent properties per weight.

The particle size of the coated carbon material is preferably one having a particle size distribution in the range of 0.1 to 150 μm, and more preferably 1% or less in this particle size distribution is 10% or less on a volume basis. If the particles having a particle size of 1 μm or less exceed 10% on a volume basis, the specific surface area increases, and the battery characteristics deteriorate, which is not preferable.

The coated carbon material obtained in the present invention can be filled in a mold in a powder state, molded under pressure, and then fired to obtain a carbon block or a graphite block having a uniform composition. It is.

Examples of the raw material for the carbon material for forming the coating include aromatic hydrocarbons such as naphthalene, phenanthrene, acenaphthylene, anthracene, triphenylene, pyrene, chrysene, and perylene; Tars, pitches, asphalts, and oils containing pitches or a mixture of these aromatic hydrocarbons as main components are mentioned, and their origin is not limited to petroleum and coal. In the present specification, these materials for forming a coating carbon material are simply referred to as “(petroleum-based or coal-based).
Heavy oil etc. " Although it is disadvantageous in terms of cost, it is also possible to use various thermosetting resins as a raw material for forming a coating.

When using coal-based heavy oil, tar or pitch is used in which at least a part of the primary QI present in the raw material is removed and the remaining primary QI is 3% or less (preferably 1% or less). It is preferable to use Here, primary QI means free carbon originally contained in coal tar. If primary QI exists in the raw material, it may cause problems in the electrode manufacturing process, such as inhibiting carbonization during firing, or mixing into the final product as spherical carbon particles of about 1 μm, Alternatively, the characteristics of the electrode may be deteriorated.

Normally, heavy oil is solid at room temperature, but softens and melts when heated. The temperature at which softening starts is called the softening point (SP). Further, in order to regulate the quality of heavy oil, a toluene-insoluble matter obtained by solvent fractionation with toluene is usually used. These are typical methods for defining heavy oil. In the present invention, any method can be appropriately selected for defining the quality of heavy oil.

In the present invention, the carbon material serving as the above core material and heavy oil are mixed and stirred. The stirring method is not particularly limited, for example, a ribbon mixer,
A mechanical stirring method using a screw-type kneader, a universal mixer, or the like can be given.

The stirring conditions (temperature and time) are appropriately selected according to the components of the raw materials (core material and heavy oil for coating), the viscosity of the mixture, and the like.
~ 200 ° C or the viscosity of the mixture is 5
It is more preferable to adjust the time so as to be 000 Pa · s or less. As described above, by adjusting the processing temperature and time during stirring, it is possible to control the thickness of the coating layer (also simply referred to as a coating layer) of the coating forming raw material. That is, by increasing the temperature and / or shortening the time, the thickness of the coating layer can be reduced, and conversely, by decreasing the temperature, the thickness of the coating layer can be increased. . If the stirring is not sufficient, the coating layer will not be uniform, which is not preferable. The stirring time generally has no adverse effect on the properties of the product, but if it is too long, the mass productivity is practically low,
Since it is not preferable, it may be appropriately selected.

The atmosphere during the stirring may be any of atmospheric pressure, pressurized pressure, and reduced pressure. When stirring is performed under reduced pressure, the affinity between the core material and the heavy oil is improved. Is preferred.

In the present invention, if necessary, the above-mentioned mixing is carried out in order to improve the conformity between the core material and the coating layer, to make the thickness of the coating layer uniform and to increase the thickness of the coating layer. It is also possible to repeat the stirring step a plurality of times. Further, prior to the subsequent washing step, the coated core material may be once separated and then subjected to the washing step.

Next, the coated carbon material covered with heavy oil or the like obtained as described above is subjected to a washing step. Examples of the organic solvent used for washing include toluene, quinoline, acetone, hexane, benzene, xylene, methylnaphthalene, alcohols, coal oil, and petroleum oil. Among them, toluene, quinoline, acetone, benzene, xylene, methanol, coal-based light oil / medium oil, petroleum-based light oil / medium oil, and the like are more preferable. When these organic solvents are appropriately selected, insolubles in the washing solvent can be newly imparted to the coating layer, so that the heavy oil component of the coating layer can be controlled.

The washing temperature may be determined in consideration of the finally obtained coated carbon material, particularly the properties of the surface coating layer, and is not particularly limited, but is preferably about 10 to 300 ° C.

The ratio of the solid matter at the time of washing {= core material + coating layer or impregnated layer (hereinafter simply referred to as coating layer)} to the organic solvent may be in the range of 1: 0.1 to 10 by weight. preferable.

In the washing step, it is possible to adjust the thickness of the coating layer, the remaining heavy oil component, etc. by selecting the type of solvent, washing time, washing temperature and the like. For example, when using a solvent having a strong detergency, appropriately combining conditions such as increasing the washing temperature,
While the thickness of the coating layer is reduced, the thickness of the coating layer can be increased by appropriately combining conditions such as using a solvent with low detergency and lowering the cleaning temperature. The washing time may be appropriately selected in consideration of the above conditions.

Next, the step of separating the coated carbon material and the organic solvent is performed by a method such as centrifugation, squeezing filtration, and gravity sedimentation. The temperature at the time of separation is usually in the range of about 10 to 300 ° C.

Drying of the separated coated carbon material is usually performed for 10 minutes.
It is performed in the range of 0 to 400 ° C.

[0047] The dry-coated carbon material thus obtained retains the pitch component around the core material particles even if it is subjected to carbonization treatment and further graphitization treatment, and it is difficult for the particles to fuse or aggregate. Absent.

Next, the coated carbon material dried above is fired. When carbonizing the coated carbon material, 60
It is possible to fire at a temperature of about 0 to 2000 ° C, and it is more preferable to fire at a temperature of about 900 to 1300 ° C. In the case of graphitization, firing can be performed at a temperature of about 2000 to 3000 ° C. 2500-3000 ℃
It is more preferable to bake at a temperature of the order.

In order to maintain low crystallinity while firing at a high temperature under carbonization or graphitization conditions, a low temperature range (50 to 400 ° C.) is applied to the coated heavy oil layer prior to firing the coated carbon material.
It is also possible to perform a non-graphitizing treatment with an oxidizing gas such as oxygen, ozone, carbon monoxide, sulfur oxide or the like, and then fire at a high temperature. For example, after forming a highly crystalline coating layer on a highly crystalline core material, the coating layer can be converted to low crystalline carbon by performing an oxidation treatment. Conversely, when such oxidation treatment is not performed, the coating layer can be maintained in a highly crystalline state. Such oxidation treatment is performed prior to the carbonization and firing of the coated carbon material. The carbon material obtained in this case is useful as a negative electrode material for a lithium secondary battery.

The atmosphere at the time of firing the coated carbon material is as follows:
Non-oxidizing atmospheres such as a reducing atmosphere, an inert gas stream, a closed state of an inert gas, and a vacuum state may be used. Regardless of the firing temperature, the heating rate is appropriately selected from the range of about 1 to 300 ° C./hr, and the firing time is about 6 hours to 1 month. The temperature can be raised stepwise according to the thickness of the coating layer and the like.

When performing vacuum carbonization, it is preferable to continue the reduced pressure state from the normal temperature to the maximum attained temperature or to reduce the pressure in an appropriate temperature range (preferably 500 ° C. or higher). Vacuum carbonization has the effect of removing the surface functional groups of the coated carbon material, and can reduce the irreversible capacity of the battery.

In general, an improvement in mass productivity can be expected at a high heating rate, whereas a dense coating layer can be expected at a low heating rate (10 ° C./hr or less). The temperature profile at the time of temperature increase and firing can take various forms such as a linear temperature increase, a stepwise temperature increase in which the temperature is held at regular intervals, and the like.

When the thus obtained carbon material whose periphery is covered with the carbon material for forming a coating is used as a negative electrode of a lithium secondary battery, the reactivity of the electrolyte with an organic solvent is low. Decomposition of liquid and destruction of carbon material are unlikely to occur. As a result, there is an advantage that the charge / discharge efficiency of the battery is improved and its safety is improved. Generally, graphite-based materials have an active crystallite edge (edge plan).
Since e) is oriented outward, it easily reacts with the electrolytic solution. In the present invention, the pitch component in which the basal plane (basal plane), which is a condensed polycyclic network of carbon, is oriented outward covers this active crystallite end face, so that the reaction of the electrolytic solution with the organic solvent is prevented. It is considered to be controlled.

According to the present invention, the temperature and time for immersing the carbon material as the core material in heavy oil or the like, or the type of organic solvent and the cleaning conditions (time,
By adjusting the temperature, etc., the amount of the coated heavy oil around the carbon material or the thickness of the coating layer can be controlled, so that the basal plane, which is a condensed polycyclic network of carbon, is oriented in the surface direction of the carbon material. Depending on the pitch component, a carbon material whose surface is covered can be produced.

Further, even if these carbon materials are carbonized or further graphitized, the state where the basal plane is oriented in the surface direction of the carbon material is maintained in coating the surface of the core material.
Therefore, when this carbon material is used for a negative electrode of a lithium secondary battery, it does not easily react with the organic solvent of the electrolytic solution, so that decomposition of the electrolytic solution and destruction of the carbon material do not occur. as a result,
A remarkable effect that the charge / discharge efficiency of the battery is high and the safety of the battery is excellent is obtained.

When the lithium secondary battery according to the present invention is manufactured, the coated carbon material obtained as described above is subjected to a process such as dispersion, crushing, and classification, if necessary, to obtain an appropriate particle size. Adjust and use as electrode material.

After the electrode is mixed with a known binder, an active material layer is formed on the current collector. The binder is not particularly limited, and a fluorine-based polymer such as polytetrafluoroethylene and polyvinylidene fluoride; a polyolefin-based polymer such as polyethylene and polypropylene; and synthetic rubbers can be used. As the amount of the binder in this case, based on 100 parts by weight of the active material,
Usually, it is in the range of about 3 to 50 parts by weight, more preferably 5 to 50 parts by weight.
It is about 20 parts by weight, more preferably about 5 to 15 parts by weight. If the amount of the binder is too large, the density of the active material in the electrode decreases, which is not preferable. On the other hand, if the amount of the binder is too small, the ability to retain the active material in the electrode is not sufficiently obtained, and the stability of the electrode is lowered. As a method for forming an electrode, a paste in which an active material and a binder are mixed is prepared, and a method in which an active material layer is formed on a current collector by a doctor blade, a bar coater, or the like, or an active material and a binder are used. A method in which the mixture is placed in a molding machine or the like and formed into a molded body by pressing or the like can be given.

The electrolyte of the lithium secondary battery according to the present invention includes known organic electrolytes, inorganic solid electrolytes, and the like.
A polymer solid electrolyte or the like can be used.

Among these, an organic electrolyte is particularly preferred from the viewpoint of ionic conductivity. As the solvent for the organic electrolyte, propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, γ-
Esters such as butyrolactone; substituted tetrahydrofurans such as tetrahydrofuran and 2-methyltetrahydrofuran; ethers such as dioxolane, diethyl ether, dimethoxyethane, diethoxyethane and methoxyethoxyethane; dimethylsulfoxide, sulfolane, methylsulfolane, acetonitrile, methyl formate, methyl formate,
Examples thereof include methyl acetate, and these can be used alone or in combination. Examples of the electrolyte include lithium salts such as lithium perchlorate, lithium borofluoride, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium halide, and lithium chloride aluminate. Of 1
Species or two or more species can be used. The organic electrolyte is prepared by dissolving the electrolyte in the above-mentioned solvent. Needless to say, the solvent and the electrolyte used when preparing the electrolytic solution are not limited to those listed above.

Examples of the inorganic solid electrolyte include nitrides, halides, oxyacid salts, and phosphorus sulfide compounds of Li. More specifically, Li ₃ N, LiI, Li ₃ N—LiI—LiOH, and LiSi
_{O 4, LiSiO 4 -LiI-LiOH} , etc. _{Li 3 PO 4 -Li 4 SiO 4} , Li 2 SiS 3 is exemplified.

Examples of the organic solid electrolyte include a substance composed of the above-mentioned electrolyte and a polymer that dissociates the electrolyte, a substance having an ion dissociating group in the polymer, and the like. Examples of the polymer that dissociates the electrolyte include a polyethylene oxide derivative and a polymer containing the derivative, a polypropylene oxide derivative and a polymer containing the derivative, and a phosphate ester polymer. A polymer matrix material containing the above-mentioned aprotic polar solvent, a mixture of a polymer containing an ion-dissociating group and the above-mentioned aprotic polar solvent, and a material obtained by adding polyacrylonitrile to an electrolytic solution can also be used. Furthermore, it is also possible to use an inorganic solid electrolyte and an organic solid electrolyte together.

As the positive electrode in the lithium secondary battery of the present invention, for example, an oxide containing lithium can be used as a positive electrode active material according to a conventional method. Specific examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , LiMn
O ₂ , Li _x M _y N _z O ₂ , which is an analog of these compounds, where M is F
e, any of Co, Ni and Mn, where N is a transition metal, 4B
Group metal or group 5B metal), LiMn ₂ O ₄ , or its related compound LiMn _2-x N _y O ₄ (where N represents a transition metal, group 4B metal or group 5B metal), LiVO _2, etc. And a conductive material, a binder, and in some cases, a solid electrolyte are mixed to form a positive electrode. The mixing ratio of these materials can be about 5 to 50 parts by weight of the conductive material and about 1 to 30 parts by weight of the binder with respect to 100 parts by weight of the active material. Such a conductive material is not particularly limited, and carbons such as known carbon black (such as acetylene black, thermal black, and channel black), graphite powder, and metal powder can be used. Also,
The binder is not particularly limited, and a known fluorine-based polymer such as polytetrafluoroethylene and polyvinylidene fluoride; a polyolefin-based polymer such as polyethylene and polypropylene; and synthetic rubbers can be used. If the compounding amount of the conductive material is less than 5 parts by weight or the compounding amount of the binder is more than 30 parts by weight, the resistance or polarization of the electrode becomes large, and the discharge capacity becomes small. The next battery cannot be manufactured. If the conductive material is more than 50 parts by weight (the relative proportion varies depending on the type of conductive material mixed),
Since the amount of active material contained in the electrode is reduced, the discharge capacity as a positive electrode is reduced. When the binder is smaller than 1 part by weight, the binding ability is lost.On the other hand, when the binder is larger than 30 parts by weight, similarly to the case of the conductive material, the amount of the active material contained in the electrode is reduced, and As described above, the resistance or polarization of the electrode increases and the discharge capacity decreases, which is not practical. In producing the positive electrode, it is preferable to perform a heat treatment at a temperature near the melting point of each binder in order to improve the binding property.

Examples of the separator for holding the electrolytic solution include well-known non-woven fabrics or woven fabrics of synthetic resin fibers, glass fibers, and natural fibers having electrical insulation properties, and powder compacts of alumina and the like. Among them, nonwoven fabrics such as synthetic resins such as polyethylene and polypropylene are preferable from the viewpoint of quality stability and the like. Some of these synthetic resin nonwoven fabrics have a function to add a function of shutting off between the positive electrode and the negative electrode when the battery is abnormally heated, and the separator is melted by heat. Can be used for The thickness of the separator is not particularly limited, as long as it can hold a required amount of electrolytic solution and can prevent a short circuit between the positive electrode and the negative electrode, and is usually about 0.01 to 1 mm, and preferably about 0.02 mm.
It is about 0.05 mm.

Examples of the current collector include, but are not limited to, known metal foils such as copper, nickel, stainless steel, aluminum, and titanium, meshes, and porous bodies.

Effect of the Invention In the present invention, a carbon material, particularly a graphite material having a high degree of crystallinity, is immersed in coal or petroleum heavy oil such as tar or pitch, and the coated carbon material is subjected to heavy load. After being separated from high-grade oil, etc., it is washed with an organic solvent and dried,
A novel carbon material in which the surface of the carbon material as the core material is covered with heavy oil or the like can be obtained.

Further, by carbonizing a graphite-based carbon material whose surface is uniformly covered with a pitch at 600 ° C. to 2000 ° C., the core material is made of a graphite-based material having a high degree of crystallinity, and the surface is crystallized. A carbon material having a peculiar structure that is covered with a carbon-based material having a low degree of conversion can be manufactured.

According to the production method of the present invention, after the carbon material as the core material is coated with heavy oil such as pitch and tar,
Even when washing, drying and baking are performed, fusion or aggregation of the particles does not occur, so that the obtained carbon material does not need to be pulverized, and so-called “sharp” spherical particles are obtained. In addition, there is no material deterioration factor such as mixing of impurities due to grinding.

When a non-aqueous secondary battery or a solid electrolyte battery is manufactured using the coated carbon material obtained by the present invention, in particular, a carbon material obtained by coating the surface of a graphite material with heavy oil or the like or a fired product thereof. Thus, it is possible to manufacture a battery having both excellent charge and discharge characteristics and safety.

The method of the present invention uses inexpensive natural graphite, artificial graphite or the like as a core material, uses inexpensive pitch or tar as a coating material, is simple in its production method, and is very low in mass productivity. Therefore, an inexpensive negative electrode material for a high-performance lithium secondary battery can be obtained.

Further, in the present invention, the combination of the core material and the surface material is as follows: low-crystalline carbon material + low-crystalline carbon material, low-crystalline carbon material + high-crystalline carbon material, high-crystalline carbon material + Four combinations of a low-crystalline carbon material, a high-crystalline carbon material and a high-crystalline carbon material are possible, and if two firing steps (carbonization firing and graphitization firing) are considered, eight types of carbon can be obtained. The material is obtained. Among them, carbonized high crystalline carbon material + low crystalline carbon material and high crystalline carbon material + high crystalline carbon material, graphitized high crystalline carbon material + low crystalline carbon material, etc. When a carbon material composed of a combination is used, it is particularly useful as a negative electrode material for a lithium secondary battery because it has low reactivity with an electrolytic solution and exhibits excellent charge / discharge characteristics.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described with reference to the following examples. Various measurements in each of the following examples were performed as follows. 1. Measurement of Particle Size The central particle size and the particle size distribution of the particles were measured using “FRA9220 Microtrack” manufactured by Nikkiso Co., Ltd. 2. Measurement of coating ratio and coating thickness For the carbon component derived from heavy oil covering the surroundings of the core material before firing, solvent analysis was performed according to the method specified in JIS K2425, and the quinoline insoluble content (% ) And measure "10
The quinoline-soluble matter (%) was calculated from “0- (quinoline-insoluble matter)”. The amount of the quinoline-soluble component is the amount of the coating-forming carbon material.

Weight ratio of carbon material for coating formation / (carbon material for core material + carbon material for coating formation) (covering ratio as defined above)
Was calculated by the method described above. 3. Measurement of specific surface area The specific surface area was measured using “ASAP2400 / nitrogen adsorption BET specific surface area measuring device” manufactured by Micromeritex Corporation. 4. Measurement of true specific gravity True specific gravity was measured according to the method specified in JIS R7212. 5. Measurement of crystallite size by X-ray wide-angle diffraction method Measurement of crystallite size (Lc, La) by X-ray wide-angle diffraction method is a known method, that is, "Carbon Materials Experimental Technique 1 pp55
~ 63 Carbon Materials Society of Japan (Science and Technology Co., Ltd.) "Form factor K for determining crystallite size
Was used as 0.9. 6. Raman spectroscopy Further, the surface properties of the carbon material are observed by Raman spectroscopy using a 514.5 nm argon laser.
The peak of this was determined R value as the peak intensity ratio of 1360cm ^-1 / 1580cm ^-1. 7. Measurement of the amount of gas generated when the negative electrode is immersed in the electrolyte and kept at high temperature Pitch-coated carbon material (pitch-coated graphite) in a nitrogen atmosphere
It was graphitized by firing at 2800 ° C. for 1 hour. 95 parts by weight of graphitized pitch-coated graphite and dispersion type
5 parts by weight of PTFE (“D-1” manufactured by Daikin Industries, Ltd.) were mixed, uniformly stirred in a liquid phase, and dried to form a paste. 0.25 g of this negative electrode material was molded by a press machine to prepare a negative electrode body having a diameter of 2 cm, followed by vacuum drying at 200 ° C. for 6 hours.

Next, this negative electrode is charged in the electrolyte until the potential becomes 0 V, and the charged negative electrode is placed in a beaker cell containing 25 ml of the electrolyte and heated at 60 ° C. for 6 hours to be graphitized pitch-coated graphite. The amount of gas generated per gram was measured.

The electrolyte used was 1 moldm ^-3 of LiClO ₄
Mixed solvent of ethylene carbonate, diethyl carbonate, and methyl propionate (3: 3:
4) was used. 8. Preparation of Nonaqueous Battery and Measurement of Battery Characteristics The positive electrode is generally prepared by mixing a positive electrode material with a conductive material and a binder. In this case, as the conductive material, carbon materials such as carbon black and graphite or metal materials such as metal powder and metal wool are appropriately used. The binder can be mixed as powder, but in order to further improve dispersibility and improve binding,
In some cases, those dispersed in a solution or those dissolved therein are mixed. In addition, when the material dispersed or dissolved in the solution is used, it is necessary to remove the solution by means such as vacuum treatment or heat treatment. Further, depending on the type of the binder, it is possible to further enhance the binding property by performing a heat treatment at a temperature near the melting point.

In the embodiment of the present invention, 100 parts by weight of LiCoO ₂ was used as a positive electrode material, 10 parts by weight of acetylene black as a conductive material and 10 parts by weight of PTFE powder as a binder were molded into an electrode having a diameter of 10 mm. A positive electrode body was obtained.

In the examples of the present application, the negative electrode body was manufactured as follows.

First, the pitch-coated graphite was placed in a nitrogen atmosphere at 1000
It was calcined at ℃ for 1 hour and carbonized. This carbonized pitch-coated graphite 9
5 parts by weight and 5 parts by weight of a dispersion type PTFE (“D-1” manufactured by Daikin Industries, Ltd.) were mixed, uniformly stirred in a liquid phase, and dried to form a paste. further,
30 mg of this negative electrode material was molded by a press machine, and the diameter was 10 mm.
After preparing the negative electrode body described above, it was vacuum-dried at 200 ° C. for 6 hours.

Further, pitch-coated graphite was placed in a nitrogen atmosphere at 2800
It was baked at ℃ for 1 hour to be graphitized. 95 parts by weight of the graphitized pitch-coated graphite and 5 parts by weight of dispersion type PTFE ("D-1" manufactured by Daikin Industries, Ltd.) are mixed, uniformly stirred in a liquid phase, dried, and then dried. Shape. The negative electrode material (30 mg) was molded by a press machine to prepare a negative electrode body having a diameter of 10 mm, and then vacuum dried at 200 ° C. for 6 hours.

As the separator, a nonwoven polypropylene fabric was used.

In the case of using carbonized pitch-coated graphite as the negative electrode body, propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved was used as the electrolytic solution. When using graphitized pitch-coated graphite, a mixed solvent of ethylene carbonate, diethyl carbonate and methyl propionate (volume ratio of 3: 3: 4) in which 1 moldm- ³ of LiClO ₄ was dissolved was used.

The discharge characteristics of the coin-type lithium secondary battery manufactured using the positive electrode body, the negative electrode body, the separator and the electrolyte obtained as described above were measured. Measurement is 1mA /
The test was performed under constant current charge / discharge of cm ² and the discharge capacity was
The capacitance was set to drop to 1.2V. 9. Preparation of Solid Electrolyte Battery and Measurement of Battery Characteristics Paste negative electrode material prepared in the same manner as in the section of preparation of non-aqueous battery (8 above) is applied to both sides of copper foil of 0.02 mm thickness and dried. Rolled, thickness 0.10mm, width 55mm, length 90mm
Negative electrode plate.

Polyethylene oxide (molecular weight 600,000) and Li
ClO ₄ was dissolved in acetonitrile, and this solution was cast on a PTFE membrane (“Teflon” manufactured by DuPont) in a glove box under an argon atmosphere, and then left at 25 ° C. in a glove box to evaporate the solvent. And further dried to prepare a solid electrolyte (PFO) ₈ .LiClO ₄ .

Using the carbonized pitch-coated graphite or graphitized pitch-coated graphite as the negative electrode obtained above, a solid electrolyte and LiCoO ₂ as the positive electrode, (P) was used as the solid electrolyte.
A film-type lithium secondary battery was fabricated using FO) ₈ · LiClO ₄ .

The discharge characteristics of the lithium secondary battery obtained above were measured. The measurement was performed under a constant current charge / discharge of 1 mA / cm ² , and the discharge capacity was a capacity until the battery voltage dropped to 1.2 V. Example 1 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity = 2.25 g / cm ² ) 50 g and coal tar pitch with a softening point of 80 ° C with primary QI removed (quinoline insoluble trace, toluene insoluble 30%) 100
g in a 500 ml separate flask at 200 ° C under normal pressure.
The mixture was stirred and mixed for an hour to obtain a crude pitch-coated graphite. 1 part of toluene was added to 1 part of the obtained crude pitch-coated graphite, and the mixture was washed at 80 ° C. for 1 hour with stirring, and then filtered to obtain a purified pitch-coated graphite. The center particle diameter D50 of the purified pitch-coated graphite was measured and found to be 7.7 μm. Since the center particle diameter D50 of graphite as the core material was 7.5 μm, the thickness of the pitch layer was 0.1 μm.

Table 1 shows the quinoline-soluble content, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the value of the quinoline soluble component is 9.6%, the coating ratio of the purified pitch-coated graphite is 0.096.

This purified pitch-coated graphite is placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite.
In addition, as a result of measuring the particle size distribution of the purified pitch-coated graphite,
It was confirmed that it had a distribution of 0.1 to 150 μm as in the case of the core material, and the result of X-ray diffraction measurement was similar to that of the core material.
Furthermore, the comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that the carbonized pitch forming the coating layer had a lower crystallinity than the core material. Further, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with the carbonized pitch forming the coating layer, and the edge portion was rounded.

A negative electrode was produced using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was produced using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics.

Further, a negative electrode was manufactured using graphite coated with carbonized pitch, and a solid electrolyte lithium secondary battery was manufactured.
Table 3 shows the measurement results of the charge / discharge characteristics. Example 2 Purified pitch-coated graphite obtained in the same manner as in Example 1 was used for 10
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) under vacuum of torr, and vacuum carbonized. The specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained vacuum carbonized pitch-coated graphite are also shown in Table 1. As a result of the particle size distribution measurement of this vacuum carbonized pitch-coated graphite, 0.1 to 150 μm
Was confirmed, and the result of X-ray diffraction measurement was the same as that of the core material. Furthermore, from the comparison of the R value between the core material and the vacuum carbonized pitch-coated graphite, it was found that the carbonized pitch forming the coating layer had a lower crystallinity than the core material.
Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with the vacuum carbonized pitch forming the covering layer, and the edge portion was rounded.

A negative electrode was manufactured using the vacuum carbonized pitch-coated graphite, and a nonaqueous secondary battery was manufactured using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 3 Purified pitch-coated graphite obtained in the same manner as in Example 1 was calcined at 2800 ° C. for 1 hour in a nitrogen atmosphere to be graphitized. Table 1 also shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained graphitized pitch-coated graphite. As a result of measuring the particle size distribution of the graphitized pitch-coated graphite,
It was confirmed that it had a distribution of 0.1 to 150 μm as in the case of the core material, and the result of X-ray diffraction measurement was similar to that of the core material.
Furthermore, a comparison of the R value between the core material and the graphitized pitch-coated graphite revealed that the graphitized pitch forming the coating layer had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered by the graphitized pitch forming the covering layer, and the edge portion was rounded.

A negative electrode was prepared using the graphitized pitch-coated graphite, and a mixed solvent of ethylene carbonate, diethyl carbonate and methyl propionate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution (3: 3: 4) Was used to produce a non-aqueous secondary battery.

The amount of gas generated in the electrolytic solution of the graphitized pitch-coated graphite was measured. Table 2 also shows the measurement results of the charge and discharge characteristics and the gas generation amount. Example 4 A refined pitch-coated graphite obtained in the same manner as in Example 1 was placed in a lead hammer furnace capable of very slowly raising the temperature to 1000.
℃ (reducing atmosphere, heating rate 5 ° C / hr or less) and carbonized. Specific surface area, true specific gravity, R of this carbonized pitch-coated graphite
The values and the volume-based integrated value of the particles having a particle size of 1 μm or less are also shown in Table 1. As a result of measuring the particle size distribution of the carbonized pitch-coated graphite, it was confirmed that the graphite had a distribution of 0.1 to 150 μm as in the case of the core material, and the X-ray diffraction measurement result was the same as that of the core material. Furthermore, the comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that the carbonized pitch forming the coating layer had a lower crystallinity than the core material. Further, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with the carbonized pitch forming the coating layer, and the edge portion was rounded.

A negative electrode was manufactured using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was manufactured using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 5 Purified pitch-coated graphite obtained in the same manner as in Example 1 was calcined in a nitrogen atmosphere at 1300 ° C. for 1 hour (heating rate 25 ° C./hr).
Carbonized. Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the carbonized pitch-coated graphite.
Are shown together. As a result of measuring the particle size distribution of the carbonized pitch-coated graphite, it was confirmed that the graphite had a distribution of 0.1 to 150 μm as in the case of the core material, and the X-ray diffraction measurement result was the same as that of the core material. Furthermore, the comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that the carbonized pitch forming the coating layer had a lower crystallinity than the core material. Further, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with the carbonized pitch forming the coating layer, and the edge portion was rounded.

A negative electrode was manufactured using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was manufactured using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 6 Purified pitch-coated graphite obtained in the same manner as in Example 1 was oxidized at 300 ° C. for 8 hours in an air atmosphere in a thermo-hygrostat. Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained oxidized purified pitch-coated graphite. This oxidized and refined pitch-coated graphite is heated at 1000 ° C for 1 hour in a nitrogen atmosphere (heating rate 25 ° C / hr).
Fired and carbonized. Table 1 also shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite. As a result of measuring the particle size distribution of the carbonized pitch-coated graphite, it was confirmed that the graphite had a distribution of 0.1 to 150 μm as in the case of the core material, and the X-ray diffraction measurement result was the same as that of the core material. Furthermore, by comparing the R value of the core material and the carbonized pitch-coated graphite, the carbonized pitch forming the coating layer is:
It was found that the crystallinity was lower than that of the core material. In addition, SEM
As a result of the observation, it was confirmed that the artificial graphite as the core material was covered with the carbonized pitch forming the coating layer, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 7 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution = 0.1 to
150 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity = 2.25 g / cm ³ ) 50 g and 100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) with a softening point of 80 ° C with primary QI removed in advance 500
The mixture was placed in a ml flask and stirred and mixed at 200 ° C. for 2 hours to obtain a coarse pitch-coated graphite.

1 part of toluene was added to 1 part of the obtained crude pitch-coated graphite, washed with stirring at 20 ° C. for 1 hour, and filtered to obtain purified pitch-coated graphite. When the center particle diameter D50 of the purified pitch-coated graphite was measured, 7.9 μm
Met. The center particle size D50 of artificial graphite as core material is 7.5μ
m, the thickness of the pitch layer is 0.2 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the value of the quinoline-soluble component is 20.4%, the coating ratio of the purified pitch-coated graphite is 0.204.

The obtained purified pitch-coated graphite was calcined in a nitrogen atmosphere at 1000 ° C. for 1 hour (heating rate: 25 ° C./hr) and carbonized. Table 1 also shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the carbonized pitch-coated graphite. As a result of measuring the particle size distribution of the carbonized pitch-coated graphite,
It was confirmed that it had a distribution of 0.1 to 150 μm as in the case of the core material, and the result of X-ray diffraction measurement was similar to that of the core material.
Furthermore, the comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that the carbonized pitch forming the coating layer had a lower crystallinity than the core material. Further, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with the carbonized pitch forming the coating layer, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 8 The purified pitch-coated graphite obtained in the same manner as in Example 7 was calcined at 2800 ° C. for 1 hour in a nitrogen atmosphere to be graphitized. Table 1 also shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained graphitized pitch-coated graphite. As a result of measuring the particle size distribution of the graphitized pitch-coated graphite,
It was confirmed that it had a distribution of 0.1 to 150 μm as in the case of the core material, and the result of X-ray diffraction measurement was similar to that of the core material.
Furthermore, a comparison of the R value between the core material and the graphitized pitch-coated graphite revealed that the graphitized pitch forming the coating layer had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered by the graphitized pitch forming the covering layer, and the edge portion was rounded.

A negative electrode was prepared using the graphitized pitch-coated graphite, and a mixed solvent of ethylene carbonate, diethyl carbonate and methyl propionate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution (3: 3: 4 ) Was used to produce a non-aqueous secondary battery. In addition, the amount of gas generated in the electrolytic solution of the graphitized pitch-coated graphite was measured. Table 2 also shows the measurement results of the charge and discharge characteristics and the gas generation amount. Example 9 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution = 0.1 to
150 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity = 2.25 g / cm ³ ) 100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) with 50 g and a softening point of 80 ° C with primary QI removed in advance
g was placed in a 500 ml separate flask and stirred and mixed at 200 ° C. for 2 hours under reduced pressure (suction with a vacuum pump, degree of reduced pressure of 50 torr) to obtain crude pitch-coated graphite.

To 1 part of the obtained crude pitch-coated graphite, 1 part of toluene was added, washed with stirring at 80 ° C. for 1 hour, and filtered to obtain a purified pitch-coated graphite. The center particle diameter D50 of the purified pitch-coated graphite was 7.7 μm. Since the central particle diameter D50 of the artificial graphite as the core material was 7.5 μm, the thickness of the pitch layer was 0.1 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the purified pitch-coated graphite. Quinoline solubles value of 1
Since it is 0.4%, the coating ratio of the purified pitch-coated graphite is 0.104.

This purified pitch-coated graphite was placed in a nitrogen atmosphere at 10
It was baked at 00 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized. Table 1 also shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite. As a result of measuring the particle size distribution of the graphitized pitch-coated graphite,
It was confirmed that it had a distribution of 0.1 to 150 μm as in the case of the core material, and the result of X-ray diffraction measurement was similar to that of the core material.
Furthermore, a comparison of the R value between the core material and the graphitized pitch-coated graphite revealed that the graphitized pitch forming the coating layer had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered by the graphitized pitch forming the covering layer, and the edge portion was rounded.

A negative electrode was manufactured using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was manufactured using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 10 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution = 0.1 to
150 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity = 2.25 g / cm ³ ) 100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) with 50 g and a softening point of 80 ° C with primary QI removed in advance
g was placed in a 500 ml separate flask and stirred and mixed at 200 ° C. for 2 hours to obtain coarse pitch-coated graphite.

1 part of oil in tar was added to 1 part of the obtained crude pitch-coated graphite, washed with stirring at 20 ° C. for 1 hour, and filtered to obtain purified pitch-coated graphite. When the center particle diameter D50 of the purified pitch-coated graphite was measured, it was 7.6 μm.
m. Since the core particle diameter D50 of graphite of the core material was 7.5 μm, the thickness of the pitch layer was 0.05 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of this purified pitch-coated graphite. The value of the quinoline soluble component is
Since it is 8.8%, the coating ratio of the purified pitch-coated graphite is 0.088.

The purified pitch-coated graphite was placed in a nitrogen atmosphere at 10
It was baked at 00 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized. The specific surface area, true specific gravity, R value and 1
Table 1 also shows the volume-based integrated value of the particles having a particle size of μm or less.
As a result of the particle size distribution measurement of the graphitized pitch-coated graphite, it was confirmed that the core material had a distribution of 0.1 to 150 μm, like the core material.
The X-ray diffraction measurement results were the same as those of the core material. Furthermore, by comparing the R value of the core material and the graphitized pitch-coated graphite,
The graphitized pitch forming the coating layer was found to have a lower crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered by the graphitized pitch forming the covering layer, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 11 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution = 0.1 to
150 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity = 2.25 g / cm ³ ) 50 g and a coal tar pitch with a softening point of 80 ° C with primary QI removed (quinoline insoluble trace, toluene insoluble 30%) 200
g was placed in a 1000 ml separate flask and stirred and mixed at 200 ° C. for 2 hours to obtain coarse pitch-coated graphite.

[0108] 1 part of toluene was added to 1 part of the obtained crude pitch-coated graphite, and the mixture was washed with stirring at 80 ° C for 1 hour, and then filtered to obtain purified pitch-coated graphite. When the center particle diameter D50 of the purified pitch-coated graphite was measured, 7.9 μm
Met. Since the core particle diameter D50 of the graphite graphite was 7.5 μm, the thickness of the pitch layer was 0.2 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the purified pitch-coated graphite. Quinoline solubles value of 1
Since it is 7.3%, the coating ratio is 0.173.

The purified pitch-coated graphite was placed in a nitrogen atmosphere at 10
It was baked at 00 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized. The specific surface area, true specific gravity, R value and 1
Table 1 also shows the volume-based integrated value of the particles having a particle size of μm or less.
As a result of measuring the particle size distribution of the carbonized pitch-coated graphite, it was confirmed that the graphite had a distribution of 0.1 to 150 μm as in the case of the core material, and the X-ray diffraction measurement result was the same as that of the core material. Furthermore, the comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that the carbonized pitch forming the coating layer had a lower crystallinity than the core material. Further, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with the carbonized pitch forming the coating layer, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 12 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution = 0.1 to
150 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8m ² / g, R value = 0.26, true specific gravity = 2.25g / cm ³ ) 50g and primary Q
100 g of coal tar pitch (3.9% quinoline-insoluble matter, 34% toluene-insoluble matter) having a softening point of 80 ° C without removing I
The mixture was placed in a 00 ml separate flask and stirred and mixed at 200 ° C. under normal pressure for 2 hours to obtain a coarse pitch-coated graphite.

To 1 part of the crude pitch-coated graphite thus obtained, 1 part of toluene was added, washed with stirring at 80 ° C. for 1 hour, and filtered to obtain a purified pitch-coated graphite. The center particle diameter D50 of the purified pitch-coated graphite was 7.9 μm. Since the core particle diameter D50 of the graphite graphite was 7.5 μm, the thickness of the pitch layer was 0.2 μm.

Table 1 shows the coating ratio, specific surface area, and true specific gravity of the purified pitch-coated graphite. Quinoline solubles
Since it is 7.5%, the covering ratio is 0.075.

The purified pitch-coated graphite was placed in a nitrogen atmosphere at 10
It was baked at 00 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized. The specific surface area, true specific gravity, R value and 1
Table 1 also shows the volume-based integrated value of the particles having a particle size of μm or less.
As a result of measuring the particle size distribution of the carbonized pitch-coated graphite, it was confirmed that the graphite had a distribution of 0.1 to 150 μm as in the case of the core material, and the X-ray diffraction measurement result was the same as that of the core material. Furthermore, the comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that the carbonized pitch forming the coating layer had a lower crystallinity than the core material. Further, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with the carbonized pitch forming the coating layer, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics. Example 13 Lumpy artificial graphite (center particle size D50 = 7.5 μm, particle size distribution = 0.1 to
150 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity = 2.25 g / cm ³ ) 50 g and 100 g of coal tar (quinoline insoluble trace, toluene insoluble 8%) having a softening point of 10 ° C. from which primary QI has been removed in advance 50
The mixture was placed in a 0 ml separate flask and mixed with stirring at 200 ° C. for 2 hours under normal pressure to obtain a coarse pitch-coated graphite.

1 part of toluene was added to 1 part of the obtained crude pitch-coated graphite, washed at 80 ° C. for 1 hour with stirring, and filtered to obtain a purified pitch-coated graphite. When the center particle diameter D50 of the purified pitch-coated graphite was measured, 7.6 μm
Met. Since the core particle diameter D50 of the graphite of the core material was 7.5 μm, the thickness of the pitch layer was 0.05 μm.

The coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite are shown in Table 1. Since the measured value of the quinoline soluble component is 7.8%, the coating ratio of the purified pitch-coated graphite is 0.078.

The purified pitch-coated graphite was placed in a nitrogen atmosphere at 10
It was baked at 00 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized. The specific surface area, true specific gravity, R value and 1
Table 1 also shows the volume-based integrated value of the particles having a particle size of μm or less.
As a result of measuring the particle size distribution of the carbonized pitch-coated graphite, it was confirmed that the graphite had a distribution of 0.1 to 150 μm as in the case of the core material, and the X-ray diffraction measurement result was the same as that of the core material. Furthermore, the comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that the carbonized pitch forming the coating layer had a lower crystallinity than the core material. Further, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with the carbonized pitch forming the coating layer, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 also shows the measurement results of the charge / discharge characteristics.

Further, a negative electrode was prepared using carbonized pitch-coated graphite, and then a solid electrolyte lithium secondary battery was prepared. Table 3 also shows the measurement results of the charge and discharge characteristics. Example 14 Graphite product of spherical mesocarbon microbeads (“MCMB-6-28” manufactured by Osaka Gas Co., Ltd., central particle size D50 = 6.0 mm, particle size distribution
= 0.1-50 μm, d002 = 0.336 nm, Lc = 50 nm, La = 90 nm, specific surface area = 3.0 m ² / g, R value = 0.42, true specific gravity = 2.20 g / cm ³ ) 50 g and softening with primary QI removed in advance 80 ° C coal tar pitch (quinoline insoluble trace, toluene insoluble 30
%) Into a 500 ml separate flask and put under normal pressure for 20 g.
The mixture was stirred and mixed at 0 ° C. for 2 hours to obtain a graphitized product of crude pitch-coated mesocarbon microbeads.

To 1 part of the obtained graphitized crude pitch-coated mesocarbon microbeads, 1 part of toluene was added, and the mixture was washed at 80 ° C. for 1 hour with stirring, filtered, and purified to obtain a purified pitch-coated mesocarbon microbead. Graphitized beads were obtained.
When the center particle diameter D50 of the graphitized mesocarbon microbeads coated with the purified pitch was measured, it was 6.2 μm.
Since the center particle diameter D50 of graphite as the core material was 6.0 μm, the thickness of the pitch layer was 0.1 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the graphitized purified pitch-coated mesocarbon microbeads.
Shown in Since the value of the quinoline-soluble component is 9.8%, the coating ratio is 0.098.

The graphitized product of the purified pitch-coated mesocarbon microbeads was calcined in a nitrogen atmosphere at 1000 ° C. for 1 hour (heating rate 25 ° C./hr) and carbonized. Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the graphitized mesocarbon microbeads coated with carbonized pitch.
Are shown together. As a result of the particle size distribution measurement of the graphitized mesocarbon microbeads coated with carbonized pitch,
It was confirmed that the particles had a distribution of 0.1 to 50 μm. further,
Comparison of the R value between the core material and the graphitized mesocarbon microbeads coated with carbonized pitch revealed that the carbonized pitch forming the coating layer had a lower crystallinity than the core material.

A negative electrode was prepared using the graphitized mesocarbon microbeads coated with carbonized pitch, and 1% was used as an electrolyte.
A non-aqueous secondary battery was manufactured using propylene carbonate in which LiClO ₄ of moldm- ³ was dissolved. Table 2 shows the measurement results of the charge / discharge characteristics. Example 15 Lumpy artificial graphite (center particle diameter D50 = 16.2 μm, particle size distribution 0.1 to
120 μm, d002 = 0.337 nm, Lc = 100 nm, La = 71 nm, specific surface area = 14.4 m ² / g, R value = 0.31, true specific gravity 1.96 g / cm ³ ) 50 g and a softening point of 80 ° C. from which primary QI was previously removed. 100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) and 100 g
The mixture was placed in a 0 ml separate flask and stirred and mixed at 250 ° C. and normal pressure for 5 hours to obtain a coarse pitch-coated graphite.

To 1 part of the obtained crude pitch-coated graphite, 3 parts of toluene was added, washed with stirring at 50 ° C. for 5 hours, and filtered to obtain purified pitch-coated graphite. When the center particle diameter D50 of the purified pitch-coated graphite was measured, 16.6
μm. The core particle size D50 of graphite as a core material is 16.2
μm, the thickness of the pitch layer was 0.2 μm.

Table 1 shows the coating ratio, specific surface area, and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline-soluble component is 11.3%, the coating ratio of the coating-forming carbon material is 0.113.

The purified pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite. As a result of the particle size distribution measurement, the powder had a distribution of 0.1 to 120 μm, and the X-ray diffraction measurement result was the same as that of the core material.
Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was produced using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was produced using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Example 16 Lumpy artificial graphite (center particle diameter D50 = 16.2 μm, particle size distribution 1 to 80
μm, d002 = 0.338 nm, Lc = 83 nm, La = 63 nm, specific surface area = 6.8
m ² / g, R value = 0.38, true specific gravity 2.02 g / cm ³ ) 50 g and 100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) having a softening point of 80 ° C. with primary QI removed in advance And stirred and mixed at 250 ° C. and normal pressure for 5 hours to obtain a coarse pitch-coated graphite. To 1 part of the obtained crude pitch-coated graphite, 3 parts of toluene was added, and the mixture was stirred at 50 ° C.
After a washing treatment for 5 hours, filtration was performed to obtain a purified pitch-coated graphite. The center particle diameter D50 of the purified pitch-coated graphite was measured and found to be 12.0 μm. Since the center particle diameter D50 of graphite as the core material was 11.6 μm, the thickness of the pitch layer was 0.2 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline-soluble component is 12.3%, the coating ratio is 0.123.

This purified pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite. As a result of the particle size distribution measurement, the powder had a distribution of 1 to 80 μm, and the X-ray diffraction measurement result was the same as that of the core material. Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Example 17 Scale-like artificial graphite (center particle diameter D50 = 18.9 μm, particle size distribution 0.1
150150 μm, d002 = 0.340 nm, Lc = 42 nm, La = 50 nm, specific surface area = 9.2 m ² / g, R value = 0.49, true specific gravity 1.82 g / cm ³ ) 50 g and softening point 80 ° C. from which primary QI was previously removed 100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) and 100 g
The mixture was placed in a 0 ml separate flask and stirred and mixed at 250 ° C. and normal pressure for 5 hours to obtain a coarse pitch-coated graphite. To 1 part of the obtained crude pitch-coated graphite, 3 parts of toluene was added, and 50 parts were stirred.
After washing at 5 ° C. for 5 hours, the solution was filtered to obtain purified pitch-coated graphite. The center particle diameter D50 of this refined pitch-coated graphite
Was 19.3 μm. Since the center particle diameter D50 of graphite as a core material was 18.9 μm, the thickness of the pitch layer was 0.2 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline-soluble component is 10.6%, the coating ratio is 0.106.

The purified pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite. As a result of the particle size distribution measurement, the powder had a distribution of 0.1 to 150 μm, and the X-ray diffraction measurement result was the same as that of the core material.
Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

Using the carbonized pitch-coated graphite, a negative electrode
1moldm as electrolyte^-3LiClO_FourWas dissolved
Producing non-aqueous secondary batteries using propylene carbonate
Made. Table 2 shows the measurement results of the charge / discharge characteristics. Example 18 Whisker-like artificial graphite (center particle size D50 = 23.8 μm, particle size
Distribution 0.1-150 μm, d002 = 0.347 nm, Lc = 25 nm, La = 15 nm,
Specific surface area = 13.5m^Two/ g, R value = 0.68, true specific gravity 1.60g / cm ^Three) 50g
And a coal tar pit with a softening point of 80 ° C
J (quinoline insoluble trace, toluene insoluble 30%) 100
g in a 1000 ml separate flask, and 5
The mixture was stirred and mixed for an hour to obtain a crude pitch-coated graphite. Got
3 parts of toluene are added to 1 part of the coarse pitch-coated graphite, and the mixture is stirred.
After washing for 5 hours at 50 ° C under stirring, filtration and purification
Pitch-coated graphite was obtained. The center of this refined pitch-coated graphite
The measured particle diameter D50 was 24.2 μm. As a core material
The center particle diameter D50 of all the graphites was 23.8 μm.
The thickness of the layer is 0.2 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline-soluble component is 13.1%, the coating ratio of the coating-forming carbon material is 0.131.

This refined pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite. As a result of the particle size distribution measurement, the powder had a distribution of 0.1 to 150 μm, and the X-ray diffraction measurement result was the same as that of the core material.
Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was produced using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was produced using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Example 19 Lumpy artificial graphite (center particle size D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity 2.25 g / cm ³ ) 50 g and primary
500 g of 100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) having a softening point of 80 ° C from which QI has been removed
And stirred and mixed at 300 ° C. and a normal pressure for 1 hour to obtain a coarse pitch-coated graphite. 0.1 part of quinoline was added to 1 part of the obtained crude pitch-coated graphite, and 150 parts were stirred.
After a washing treatment at 10 ° C. for 10 hours, filtration was performed to obtain a purified pitch-coated graphite. The center particle diameter D50 of the purified pitch-coated graphite was measured and found to be 8.1 μm. Since the center particle diameter D50 of graphite as a core material was 7.5 μm, the thickness of the pitch layer was 0.3 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline-soluble component is 29.0%, the coating ratio is 0.290.

The purified pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 100 ° C / hr) and carbonized. Specific surface area, true specific gravity, of the obtained carbonized pitch-coated graphite,
Table 1 shows the R value and the volume-based integrated value of the particles having a particle size of 1 μm or less. As a result of the particle size distribution measurement, the powder had a distribution of 0.1 to 150 μm, and the X-ray diffraction measurement result was the same as that of the core material. By comparing the R value of the core material and the carbonized pitch-coated graphite,
It was found that carbonized pitch, which is a carbon material for forming a coating, had lower crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Example 20 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity 2.25g / cm ³⁾ 25g and advance primary
1000 g of 50 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) having a softening point of 80 ° C from which QI has been removed
And stirred and mixed at 30 ° C. and normal pressure for 3 hours to obtain a coarse pitch-coated graphite. 10 parts of acetone was added to 1 part of the obtained crude pitch-coated graphite, and the mixture was stirred at 30 ° C.
After washing for 5 hours, filtration was performed to obtain purified pitch-coated graphite. The center particle diameter D50 of the purified pitch-coated graphite was 7.8 μm. Since the center particle diameter D50 of graphite as a core material was 7.5 μm, the thickness of the pitch layer was 0.15 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline-soluble component is 15.0%, the coating ratio is 0.150.

The purified pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite.
As a result of the particle size distribution measurement, the powder had a distribution of 0.1 to 150 μm, and the X-ray diffraction measurement result was the same as that of the core material. Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was produced using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was produced using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Example 21 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity 2.25 g / cm ³ ) 50 g and primary
50 g of coal tar (quinoline-insoluble trace, 8% toluene-insoluble 8%) having a softening point of 10 ° C. from which QI has been removed is placed in a 500 ml separate flask, and stirred and mixed at 250 ° C. under normal pressure for 3 hours to obtain coarse pitch-coated graphite. Obtained. The obtained crude pitch-coated graphite 1
10 parts of tar medium oil was added to each part, and the mixture was washed at 200 ° C. for 1 hour with stirring, and then filtered to obtain purified pitch-coated graphite. When the center particle diameter D50 of the purified pitch-coated graphite was measured, it was 7.5 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline soluble component is 2.0%, the coating ratio is 0.020.

The purified pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite.
As a result of the particle size distribution measurement, the powder had a distribution of 0.1 to 150 μm, and the X-ray diffraction measurement result was the same as that of the core material. Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Example 22 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity 2.25 g / cm ³ ) 50 g and primary
100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) with a softening point of 80 ° C after removal of QI
The resulting mixture was stirred and mixed at 250 ° C. and normal pressure for 3 hours to obtain a coarse pitch-coated graphite. 1 part of the obtained crude pitch-coated graphite was added with 4 parts of toluene, and stirred at 80 ° C.
, And filtered to obtain purified pitch-coated graphite. When the center particle diameter D50 of the purified pitch-coated graphite was measured, it was 7.6 μm. Since the center particle diameter D50 of graphite as the core material was 7.5 μm, the thickness of the pitch layer was
0.05 μm.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline-soluble component is 8.2%, the covering ratio is 0.082.

The purified pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 700 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite.
As a result of the particle size distribution measurement, the powder had a distribution of 0.1 to 150 μm, and the X-ray diffraction measurement result was the same as that of the core material. Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Example 23 Purified pitch-coated graphite obtained in the same manner as in Example 22 was calcined in a nitrogen atmosphere at 1500 ° C. for 2 hours (heating rate 25 ° C./hr) and carbonized. Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite. Also, as a result of the particle size distribution measurement, 0.1 to 150
It had a distribution at μm, and the result of X-ray diffraction measurement was the same as that of the core material. Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Example 24 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity 2.25 g / cm ³ ) 50 g and primary
100g of coal tar (quinoline insoluble content 2.9%, toluene insoluble content 7.8%) with adjusted softening point of 10 ° C adjusted in QI amount is put in a 1000ml separate flask, and stirred and mixed at 200 ° C under normal pressure for 2 hours to coat crude pitch. Graphite was obtained. The obtained crude pitch-coated graphite
4 parts of toluene was added to 1 part, and a washing treatment was performed at 80 ° C. for 1 hour with stirring, followed by filtration to obtain a purified pitch-coated graphite. When the center particle diameter D50 of the purified pitch-coated graphite was measured, it was 7.6 μm. Core particle size of graphite as core material
Since D50 was 7.5 μm, the thickness of the pitch layer was 0.05 μm
It is.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the obtained purified pitch-coated graphite. Since the measured value of the quinoline-soluble component is 8.7%, the covering ratio is 0.087.

The purified pitch-coated graphite was placed in a nitrogen atmosphere.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbonized pitch-coated graphite.
As a result of the particle size distribution measurement, the powder had a distribution of 0.1 to 150 μm, and the X-ray diffraction measurement result was the same as that of the core material. Comparison of the R value between the core material and the carbonized pitch-coated graphite indicated that carbonized pitch, a carbon material for forming the coating, had a lower degree of crystallinity than the core material. Furthermore, as a result of SEM observation, it was confirmed that the artificial graphite as the core material was covered with carbonized pitch, which is a carbon material for forming the coating, and the edge portion was rounded.

A negative electrode was prepared using the carbonized pitch-coated graphite, and a non-aqueous secondary battery was prepared using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics. Comparative Example 1 Lumpy artificial graphite (center particle size D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity 2.25 g / cm ³ ) were used as they were to produce a negative electrode, and propylene carbonate in which 1 moldm ^-3 of LiClO ₄ was dissolved was used as an electrolyte. A secondary battery was manufactured.

However, this battery could hardly be charged or discharged due to decomposition of the electrolytic solution.

Table 1 shows the coating ratio, specific surface area and true specific gravity of the artificial graphite used. Comparative Example 2 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity 2.25 g / cm ³ ) were used as they were to produce a negative electrode, and ethylene carbonate and diethyl carbonate in which 1 moldm ^-3 of LiClO ₄ was dissolved as an electrolytic solution.
A non-aqueous secondary battery was manufactured using a mixed solvent of methyl and methyl propionate (3: 3: 4). Further, the amount of gas generated by the graphite in the electrolytic solution was measured. Table 2 also shows the measurement results of the charge / discharge characteristics and the gas generation amount. Comparative Example 3 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
Using 10.8 m ² / g, R value = 0.26, and true specific gravity of 2.25 g / cm ³ ), a negative electrode was produced, and a solid electrolyte lithium secondary battery was produced. Table 2 also shows the measurement results of the charge and discharge characteristics and the gas generation amount. Comparative Example 4 Spherical mesocarbon microbead graphitized product (“MCMB-6-28” manufactured by Osaka Gas Co., Ltd., central particle size D50 = 6.0 μm, particle size distribution 0.1-50 μm, d002 = 0.336 nm, Lc = 50 nm, La = 90 nm, specific surface area = 3.0 m ² / g, R value = 0.42, true specific gravity 2.20 g / cm ³ ) to prepare a negative electrode as it is, and use 1 moldm ^-3 LiClO ³ as an electrolyte.
_A non-aqueous secondary battery was fabricated using a mixed solvent of ethylene carbonate, diethyl carbonate, and methyl propionate (3: 3: 4) in which ₄ was dissolved. Table 2 shows the measurement results of the charge and discharge characteristics. Comparative Example 5 Lumpy artificial graphite (center particle diameter D50 = 7.5 μm, particle size distribution 0.1 to 1
50 μm, d002 = 0.336 nm, Lc = 100 nm, La = 97 nm, specific surface area =
10.8 m ² / g, R value = 0.26, true specific gravity 2.25 g / cm ³ ) 50 g and primary
100 g of coal tar pitch (quinoline insoluble trace, toluene insoluble 30%) with a softening point of 80 ° C after removal of QI
The resulting mixture was stirred and mixed at 200 ° C. and normal pressure for 2 hours to obtain a coarse pitch-coated graphite. In a nitrogen atmosphere, the obtained crude pitch-coated graphite is not washed with an organic solvent.
It was baked at 1000 ° C for 1 hour (heating rate 25 ° C / hr) and carbonized.
After firing, when the sample was taken out, the artificial graphite powder was in a lump. The obtained lump of carbon material was pulverized with a coffee mill to obtain a powdery carbon material. Table 1 shows the specific surface area, true specific gravity, R value, and volume-based integrated value of particles having a particle size of 1 μm or less of the obtained carbon material. The R value was small, and as a result of SEM observation, it was found that the carbon material obtained by the production method of the present invention had a shape with more corners, but this was crushed, and the graphite surface was This is probably due to the new exposure.

Using this carbon material, a negative electrode was fabricated.
A non-aqueous secondary battery was manufactured using propylene carbonate in which 1 moldm- ³ of LiClO ₄ was dissolved as an electrolytic solution. Table 2 shows the measurement results of the charge / discharge characteristics.

[0157]

[Table 1]

[0158]

[Table 2]

[0159]

[Table 3]

As is clear from Table 1, the specific surface area can be reduced by coating the surface of graphite with pitch or tar. In addition, by firing the coated graphite, the specific surface area is further reduced.

As is clear from Table 2, by covering the surface of graphite with pitch or tar, the discharge capacity and charge / discharge efficiency of the non-aqueous lithium secondary battery are greatly improved. Also, by coating the surface of graphite with pitch,
The reaction with the electrolytic solution is suppressed, and the amount of gas generated is also reduced. Furthermore, by covering the surface of the graphitized MCMB with a pitch, the discharge capacity and charge / discharge characteristics of the battery can be further improved.

As is clear from Table 3, by coating the surface of graphite with pitch or tar, the discharge capacity and charge / discharge efficiency of the solid electrolyte lithium secondary battery are significantly improved.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masamitsu Katsuura 6-3-4-506 Torishima, Konohana-ku, Osaka-shi, Osaka (72) Inventor Hiroaki Matsuyoshi 2-14-2, Kanaoka, Higashi-Osaka-shi, Osaka (72 ) Inventor Naoto Nishimura 192-1 Ginga, Shinjo-cho, Kitakatsuragi-gun, Nara Prefecture 5-1-2, 1308, Shigino-nishi, Joto-ku (72) Inventor Takehito Mitate 65-4, Noguchi 65-4, Yamatotakada-shi, Nara Prefecture Tetsuya Yoneda 9-17, Azumigaoka North, Nabari City, Mie Prefecture

Claims (10)

[Claims] 1. After immersing a core carbon material in a carbon material for forming a coating, an organic solvent is added to the separated core carbon material,
A method for producing a coated carbon material having a coating layer on a surface, comprising washing, drying, and firing. 2. The core carbon material is used as a carbon material for coating formation.
A method for producing a carbon material having a coating layer on its surface, characterized by adding an organic solvent to the separated core carbon material after immersion at 10 to 300 ° C., washing, drying and firing. 3. The method for producing a coated carbon material according to claim 1, wherein an organic solvent is added to the separated core material carbon material, followed by washing at 10 to 300 ° C. 4. The method for producing a coated carbon material according to claim 1, wherein the core carbon material is immersed in the carbon material for forming a coating under reduced pressure. 5. The method for producing a coated carbon material according to claim 1, wherein the carbon material for forming a coating is a coal-based and / or petroleum-based heavy oil. 6. The method for producing a coated carbon material according to claim 1, wherein the carbon material for forming a coating is tar and / or pitch. 7. The organic solvent used for washing is at least one selected from toluene, quinoline, acetone, hexane, benzene, xylene, methylnaphthalene, alcohols, coal oil and petroleum oil. 7. The method for producing a coated carbon material according to any one of 6. 8. The method for producing a coated carbon material according to claim 1, wherein the ratio between the solid content and the organic solvent at the time of washing is in the range of 1: 0.1 to 10 by weight. 9. A coating ratio (c) defined as a weight ratio of the coating-forming carbon material / (core material + coating-forming carbon material) is as follows:
The method for producing a coated carbon material according to claim 1, wherein 0 <c ≦ 0.3. 10. The coated carbon material according to any one of claims 1 to 9, wherein the coating-forming carbon material is obtained by removing at least a part of the primary QI in advance to reduce the primary QI to 3% or less. Production method.