JPH0955209A - Negative electrode carbonaceous material for lithium secondary battery and method for producing the same - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a lithium secondary battery having a large capacity and excellent in capacity stability during charge / discharge cycles. An aromatic hydrocarbon fraction fa value is 0.40 to 0.40.
A pitch of 0.95 and formalin are mixed in the presence of an acid catalyst so that the weight ratio of formaldehyde in the formalin to the pitch is 0.05 to 0.4. Then, the mixture is heated and reacted, and then components soluble in n-hexane and toluene are removed. The obtained resinous polymer compound is carbonized at a maximum reaching temperature of 900 to 1300 ° C. to produce a negative electrode carbonaceous material. As a result, although the amount of unorganized carbon in the carbonaceous material is small and most of the carbonaceous material is composed of a six-membered ring, it has a carbon six-membered carbon as compared to conventional graphitizable carbon (for example, cokes). The average interplanar spacing between ring networks becomes very wide. Therefore, there are many sites where lithium is occluded, the capacity is large, and the diffusion rate of lithium in the solid phase of the carbonaceous material is fast, which is excellent in heavy load discharge characteristics.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a negative electrode carbonaceous material suitable for use in a lithium secondary battery and a method for producing the negative electrode carbonaceous material.

[0002]

2. Description of the Related Art Negative electrodes made of carbonaceous materials for lithium secondary batteries have been attracting attention because they show excellent durability with little capacity deterioration during charge and discharge cycles. This is because the carbonaceous material can reversibly occlude and release lithium at a base potential, and utilizes the fact that the intercalation compound between lithium and the carbonaceous material is reversibly formed. is there.

For example, when a battery is constituted by a positive electrode containing a sufficient amount of lithium, a carbonaceous material and a non-aqueous lithium ion conductive electrolyte through a separator, the battery is completely assembled in a discharged state. Become. Therefore, this type of battery cannot be discharged until it is charged after assembly. When this battery is charged in the first cycle, lithium in the positive electrode is electrochemically doped between the layers of the electrode carbonaceous material. Then, when discharging is performed, the doped lithium is dedoped and returns to the positive electrode again.

[0004]

By the way, the electric capacity per unit weight of the carbonaceous material in this case (mAh / g)
Is determined by the capacity that lithium can be occluded and released. Therefore, it is desirable that the electrochemically reversible occlusion amount of lithium be as large as possible in such a negative electrode. When electrochemically producing an intercalation compound of lithium and carbon in a battery like this type of battery (corresponding to a charging operation), theoretically, one lithium atom to six carbon atoms is required. The occluded state is the upper limit, that is, the saturated composition of the intercalation compound of lithium and the carbonaceous material.

As the negative electrode carbonaceous material satisfying such conditions, there have been conventionally used those obtained by carbonizing or graphitizing a certain kind of organic polymer compound or a composite thereof by various methods. In addition, naturally occurring carbonaceous substances such as natural graphite have been investigated.

However, in the conventional carbonaceous material, when lithium is absorbed and released at a high current density (corresponding to quick charging and heavy load discharging in battery operation, respectively), the amount of lithium that can be absorbed and released, That is, the actual situation is that the capacity of the battery is not sufficient and the electrochemical reversible storage amount is not as large as the theoretical value.

Further, in this type of carbonaceous material, although the degree varies depending on the type of electrolytic solution, the dedoping amount is 10 relative to the lithium doping amount in the first cycle.
It cannot be 0%. It is considered that the main cause of this is that some of the doped lithium amount is inactivated and remains in the carbonaceous material. When a non-aqueous electrolyte is used as the non-aqueous lithium ion conductive electrolyte, in addition to the above reason, at the same time as lithium is doped in the charging process, a part of lithium involved in this electrochemical reaction is It is also considered that the non-aqueous electrolyte is consumed for reductive decomposition. Therefore, charge and discharge are repeated in the subsequent cycles with the capacity reduced.

On the other hand, since the charge / discharge reaction is carried out by the movement of lithium ions from the positive electrode side to the negative electrode side and conversely from the negative electrode side to the positive electrode side, the amount of lithium that can be transferred becomes the charge / discharge capacity of the battery. . However, as described above, the amount that can be moved during dedoping in the first cycle is reduced, so that charge and discharge are repeated with the capacity reduced in all subsequent cycles, and the energy density of the battery is reduced. .

In view of the above circumstances, the present invention has a large lithium occlusion / desorption amount when charging / discharging at a high current density, and at the same time, has a small capacity loss generated at the time of charging in the first cycle. It is an object of the present invention to provide a negative electrode carbonaceous material for a lithium secondary battery, which can be manufactured at low cost, and which has extremely little capacity deterioration even after repeated cycles, and a manufacturing method thereof.

[0010]

That is, the invention of the negative electrode carbonaceous material for a lithium secondary battery in the present invention is a negative electrode carbonaceous material used in a lithium secondary battery provided with a positive electrode containing lithium and a non-aqueous electrolyte. In the presence of an acid catalyst, the pitch of formalin, which is a material having an aromatic hydrocarbon fraction fa value of 0.40 to 0.95, and the weight ratio of formaldehyde in the formalin to the pitch is 0.05 to. It was mixed so as to be 0.4 and reacted by heating to remove components soluble in n-hexane and toluene, and the obtained resinous polymer compound was carbonized at a maximum reaching temperature of 900 to 1300 ° C. The point is that it is a thing. The invention of the method for producing a negative electrode carbonaceous material for a lithium secondary battery among the present invention is
A pitch for producing a negative electrode carbonaceous material used in a lithium secondary battery including a positive electrode containing lithium and a non-aqueous electrolyte, wherein an aromatic hydrocarbon fraction fa value is 0.40 to 0.95. And formalin in the presence of an acid catalyst so that the weight ratio of formaldehyde in the formalin to the pitch ([weight of formaldehyde in formalin] / [weight of pitch]) is 0.05 to 0.4. Then, the reaction is carried out by heating, the components soluble in n-hexane and toluene are then removed, and the obtained resinous polymer compound is carbonized at a maximum attainable temperature of 900 to 1300 ° C.

Here, the pitch means a petroleum-based heavy oil or coal tar pitches, and coal tar obtained by cooling the petroleum-based pitch, petroleum-based heavy oil or coal during the carbonization by being discharged outside the system. In addition to pitches, it also includes catalytic cracking residual oil of vacuum gas oil and thermal cracking residual oil of naphtha.

As the pitch, it is preferable to use a condensed polycyclic aromatic hydrocarbon having 3 or less rings (preferably 2 to 3 rings) or a mixture containing this as a main component. In the case of a condensed polycyclic aromatic hydrocarbon having 4 or more rings, the boiling point thereof exceeds 450 ° C in most cases, so that it is difficult to collect those having a narrow boiling range, and there is a problem that the quality is unstable. In the case of a monocyclic aromatic hydrocarbon, since the density of the place where it reacts with formaldehyde in formalin is low, there is a problem that it is difficult to reach the bond density until cross-linking. In addition, a condensed polycyclic aromatic hydrocarbon having 4 or more rings or a monocyclic aromatic hydrocarbon can be contained as long as the amount is within a small amount.

The aromatic hydrocarbon fraction fa value is defined by the formula (1) and can be obtained by ¹³ C-NMR.

[0014]

## EQU1 ## fa value = [number of aromatic carbons in pitch] / [total number of carbons in pitch] If this fa value is smaller than 0.40, the reversible capacity of the obtained carbide capable of lithium doping / dedoping is It is not preferable because it becomes smaller. Further, the carbide obtained by using such a raw material tends to have a large specific surface area, and the loss capacity generated in the first cycle becomes large, which is not preferable as described above. In addition, the amount of the unreacted compound released outside the system by the solvent treatment in the next step is increased, which lowers the yield and raises the cost, which is not preferable.

On the contrary, when the fa value is larger than 0.95, the reactivity between the aromatic ring hydrogen and formalin becomes poor,
Graphitizable coal-based pitch coke or petroleum coke that has been used as a negative electrode for lithium secondary batteries, carbonaceous material obtained by subjecting heavy oil or pitch, etc. to infusibilization treatment as necessary. It is not preferable because a carbonaceous material having the same electrochemical characteristics as the material can be obtained. Although such a carbonaceous material has a small loss capacity generated in the first cycle and an extremely excellent capacity retention rate with charge / discharge cycles, it is not preferable because it has a small reversible capacity capable of lithium doping / dedoping.

Therefore, the fa value in the present invention is 0.4 to.
It is limited to 0.95, and more preferably 0.5 to 0.8.

The formalin used in the present invention may be any substance that produces formaldehyde under the reaction conditions of the present invention. Examples are paraformaldehyde, trioxane, hexamethylenetetramine, methylal or formals. However, formalin is particularly preferable when it is easy to handle and inexpensive is selected.

The acid catalyst used in the present invention is Bronsted acid or Lewis acid. This acid catalyst is not a hydrogen halide. As this acid catalyst, for example, toluenesulfonic acid, xylenesulfonic acid, sulfuric acid, phosphoric acid, aluminum chloride, boron trifluoride, etc. can be used.

The amount of the acid catalyst used is 0.1 to 3 with respect to the total amount of pitch and formaldehyde in formalin.
It is 0% by weight (preferably 1 to 10% by weight). When the amount of the acid catalyst used is small, the reaction rate tends to be low and the reaction rate tends to be long. The reaction tends to be insufficient unless the reaction temperature is raised. On the other hand, when the amount of the acid catalyst used is large, the reaction rate does not increase so much, which may be disadvantageous in terms of cost. In addition, the recovery of the acid catalyst and the neutralization removal may be expensive.

Since water is generated by the condensation reaction,
When the acid catalyst is a Lewis acid, it may hydrolyze to generate hydrogen halide. Hydrogen halide is
There is a problem of changing the resin that is the carbon precursor,
Further, since the acid catalyst is consumed, it is necessary to discharge the generated water out of the system as soon as possible.

The mixing ratio of formaldehyde in formalin to pitch during the reaction is a weight ratio ([weight of formaldehyde in formalin] / [weight of pitch] × 10.
0) should be 5-40%. This mixing ratio is 5
If it is less than%, the degree of cross-linking of the resin becomes small and the resin does not show thermosetting property. Therefore, easily graphitizable coal-based pitch coke or petroleum coke that has been used as a negative electrode for lithium secondary batteries. As described above, a carbonaceous material having electrochemical characteristics that are not different from those of the carbonaceous material obtained by subjecting the pitch to infusibilization treatment as required can be obtained, and thus it is not preferable as described above. On the other hand, when the mixing ratio exceeds 40%, the proportion of formaldehyde generated that does not contribute to the reaction increases, resulting in an increase in cost and the degree of cross-linking of the resin becoming too large. The surface area of carbonaceous materials tends to be very large. When such a carbonaceous material is used as the negative electrode of a lithium secondary battery, although the capacity retention rate with the progress of the charge / discharge cycle is good, the loss capacity generated in the first cycle becomes extremely large, and the charge / discharge cycle is further increased. It is not preferable because the capacity becomes small.

The reaction temperature for the heating reaction is 50 considering the raw material composition, the reaction time, and the properties of the resin produced.
It may be appropriately determined within the range of about 200 ° C.
The reaction time may be appropriately determined within the range of about 0.5 to 10 hours in consideration of the raw material composition, the reaction time, and the properties of the resin produced.

Further, in the present invention, the components soluble in n-hexane and toluene (components having low reactivity and unreacted or insufficiently reacted) are removed for the following reason. That is, when such components remain, the carbide obtained by carbonization tends to have a very large surface area, and when this is used as the negative electrode of a lithium secondary battery, it is preferable for the same reason as described above. Absent. In addition, since the residual component is basically not homogeneous with the resin component, if carbonization is performed with the residual component left, the carbonaceous material obtained will be in the state of a mixture of various carbides, and the quality of It is not preferable for stability. The hydrocarbon compounds that make up the pitch have great differences with respect to their reactivity with formaldehyde. Therefore, it is necessary to react only the highly reactive portion and extract the remaining unreacted or insufficiently reacted one.

Further, in the present invention, the resinous polymer compound is carbonized at the highest temperature of 900 to 1300 ° C. for the following reason. That is, when the carbonization temperature is lower than 900 ° C., the discharge capacity at the beginning of the charge / discharge cycle is large,
The capacity deteriorates with the charge / discharge cycle, and the loss capacity generated in the first cycle is large, which is not preferable. On the contrary, when the carbonization temperature exceeds 1300 ° C., the charge / discharge capacity decreases as the carbonization temperature rises, which is higher than that of cokes, artificial graphite, and natural graphite that have been often used in batteries of this type. It is not preferable because the capacity becomes small.

On the other hand, as the material of the positive electrode, any material may be used as long as it is used in this type of battery, but it is particularly preferable to use a material containing a sufficient amount of lithium. For example, LiMn ₂ O ₄ or the general formula LiMO ₂
(However, M represents at least one of Co and Ni. Therefore, an intercalation compound containing lithium or a composite metal oxide represented by LiCoO ₂ , LiCo _0.8 Ni _0.2 O _2, or the like) is preferable.

The non-aqueous electrolyte is prepared by appropriately combining an organic solvent and an electrolyte, and any organic solvent and electrolyte can be used as long as they are used in this type of battery. For example, propylene carbonate, ethylene carbonate, 1.
2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-
Dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, a sulfolane, LiClO ₄ as an electrolyte, LiAsF _6, LiBF _4, LiP
F _6, LiCF ₃ SO _3, a LiCl like.

According to the present invention having the above-mentioned constitution, although the amount of unorganized carbon in the carbonaceous material is small and most of the carbonaceous material is constituted by the six-membered ring, the conventional graphitizable carbon (for example,
The average interplanar spacing between carbon 6-membered ring network planes is much wider than that of coke, etc., so there are many sites where lithium is occluded and the capacity is large, and lithium in the solid phase of the carbonaceous material is large. Has a fast diffusion rate and is excellent in heavy load discharge characteristics.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Preparation of Battery FIG. 1 is a sectional view of a lithium secondary battery.

In FIG. 1, reference numeral 1 denotes a positive electrode plate, in which a weight ratio of an aqueous dispersion of LiCoO _{2 as} a positive electrode active material, carbon powder as a conductive material, and polytetrafluoroethylene (hereinafter abbreviated as PTFE) as a binder. At 100: 10:
The mixture was mixed in a ratio of 10 and kneaded in a paste form with water to be applied on both sides of an aluminum foil having a thickness of 30 μm, dried, rolled and cut into a predetermined size to prepare a strip-shaped positive electrode sheet. A part of this sheet was scraped off vertically with respect to the longitudinal direction of the sheet, and a titanium positive electrode lead plate was attached by spot welding on a current collector. Active material LiCo
O ₂ is cobalt oxide (CoO) and lithium carbonate (Li ₂
CO ₃ ) at a molar ratio of 2: 1 and mixed in air at 900 ° C.
What was heated at 9 hours was used. In addition, the ratio of the aqueous dispersion of PTFE in the mixing ratio of the above materials is the ratio of the solid content.

Reference numeral 2 denotes a negative electrode carbonaceous material electrode, which comprises a carbonaceous powder and an aqueous dispersion of PTFE as a binder in a weight ratio of 10
The kneaded product at a ratio of 0: 5 was pressed into an expanded metal made of nickel, dried and cut into a predetermined size to prepare a strip-shaped negative electrode sheet. A part of this sheet was scraped vertically with respect to the longitudinal direction of the sheet, and a nickel negative electrode lead plate was attached by spot welding on a current collector. The proportion of PTFE is the proportion of solid content as in the above.

The positive electrode 1 and the negative electrode 2 are spirally wound via a porous film separator 3 made of polypropylene and inserted into a case 4. After the insertion, the lead 5 made of titanium is spot-welded to the sealing plate 6 made of stainless steel. Reference numeral 7 is a positive electrode cap and positive electrode terminal made of aluminum, which has been spot-welded to the sealing plate 6 in advance. The negative electrode lead plate 11 is spot welded to the center position of the circular bottom surface of the case 4 which also serves as the negative electrode terminal.

Reference numeral 8 is an insulating gasket made of polypropylene. Reference numeral 10 denotes a safety valve attached so that the internal gas is released to the outside when the battery internal pressure rises due to an abnormality in the battery. Reference numeral 12 is an insulating bottom plate made of polypropylene, and has holes so as to have the same area as the space generated during winding.

After the above operation, 2.3 ml of the electrolytic solution is injected and sealed. The electrolytic solution used was one in which LiPf ₆ was dissolved in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 so as to be 1 mol / l. The size of the completed battery is AA type (14.5φmm x 50mm).

Battery test 4.2V at constant current of 300mA charging current in first cycle
The battery was charged up to 4.2V and charged at a constant voltage so as to keep the battery voltage as it was when 4.2V was reached. And
Charging was stopped when the total charging time reached 3 hours. After resting for 15 minutes, the battery was discharged at a constant current of 200 mA until the battery voltage reached 2.8V. After the second cycle, the charge / discharge cycle was repeated by the same charging / discharging method as in the first cycle, and the charge / discharge was performed up to the 100th cycle.

Comparative Example 1 A battery was produced by using a commercially available coal-based pitch coke as a negative electrode material as it was, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 2 A commercially available scaly natural graphite from China as a negative electrode material was used as it was to fabricate a battery, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 3 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.2. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
The temperature was raised to 1100 ° C. at a temperature rising rate of nitrogen gas flow rate of ° C./hour, and when the temperature reached 1100 ° C., the temperature was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 4 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.3. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
The temperature was raised to 1100 ° C. at a temperature rising rate of nitrogen gas flow rate of ° C./hour, and when the temperature reached 1100 ° C., the temperature was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 5 100 parts by weight of coal tar pitch having fa value of 0.35 was mixed with 67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluenesulfonic acid, while removing water produced during the reaction. Raise the temperature to 150 ° C, 150 ° C
And reacted for 2 hours. 1000 parts by weight of the reaction mixture
-Poured into hexane and precipitated. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace and heated to 1100 ° C. at a heating rate of 100 ° C./hour in a nitrogen stream,
When the temperature reached 0 ° C., it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 1 100 parts by weight of coal tar pitch having fa value of 0.4 was mixed with 67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluenesulfonic acid while removing water produced during the reaction. The temperature was raised to 150 ° C. and the reaction was carried out at 150 ° C. for 2 hours. The reaction mixture was added with 1000 parts by weight of n-
Poured into hexane and precipitated. 1 more of this precipitate
It was poured into 000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen gas stream,
When the temperature reached ℃, it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 2 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.4. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
The temperature was raised to 1100 ° C. at a temperature rising rate of nitrogen gas flow rate of ° C./hour, and when the temperature reached 1100 ° C., the temperature was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 3 The bottom oil obtained by fluid catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
67 parts by weight of formalin (37% formaldehyde) ([weight of formaldehyde in formalin] /
[Weight of heavy oils or pitches] = 0.25), and 20 parts by weight of paratoluenesulfonic acid are mixed, and the temperature is raised to 150 ° C. while removing water produced during the reaction, and the reaction is performed at 150 ° C. for 2 hours. Let The reaction mixture was added with 1000 parts by weight of n-
Poured into hexane and precipitated. 1 more of this precipitate
It was poured into 000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen gas stream,
When the temperature reached ℃, it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 4 100 parts by weight of coal tar pitch having a fa value of 0.6 was mixed with 67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluenesulfonic acid while removing water produced during the reaction. The temperature was raised to 150 ° C. and the reaction was carried out at 150 ° C. for 2 hours. The reaction mixture was added with 1000 parts by weight of n-
Poured into hexane and precipitated. 1 more of this precipitate
It was poured into 000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen gas stream,
When the temperature reached ℃, it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 5 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.95. This raw material 10
Formalin (37% formaldehyde) 67 in 0 parts by weight
Parts by weight, 20 parts by weight of paratoluenesulfonic acid are mixed,
While removing water produced during the reaction, the temperature was raised to 150 ° C., and the reaction was carried out at 150 ° C. for 2 hours. 100 reaction mixture
It was poured into 0 part by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. Put this resin into an electric furnace and
The temperature was raised to 1100 ° C. at a heating rate in a nitrogen stream of 00 ° C./hour, and when the temperature reached 1100 ° C., the temperature was held for 1 hour,
It was allowed to cool until the temperature inside the furnace was almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 6 100 parts by weight of coal tar pitch having fa value of 0.95 was mixed with 67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluenesulfonic acid, while removing water produced during the reaction. Raise the temperature to 150 ° C, 150 ° C
And reacted for 2 hours. 1000 parts by weight of the reaction mixture
-Poured into hexane and precipitated. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace and heated to 1100 ° C. at a heating rate of 100 ° C./hour in a nitrogen stream,
When the temperature reached 0 ° C., it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 6 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 1.0. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
The temperature was raised to 1100 ° C. at a temperature rising rate of nitrogen gas flow rate of ° C./hour, and when the temperature reached 1100 ° C., the temperature was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 7 Coal tar pitch was changed to 350 ° C. in a nitrogen stream atmosphere.
The temperature was raised to 4 hours and kept for 4 hours to obtain a heat treated coal tar pitch having a fa value of 1.5. 67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluenesulfonic acid are mixed with 100 parts by weight of this pitch, and the temperature is raised to 150 ° C. while removing water generated during the reaction, and 1
The reaction was carried out at 50 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and the temperature is 100 ° C.
At a heating rate of 1 / ° C in a nitrogen stream for 1 hour / hour,
When the temperature reached 1100 ° C., it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

The above results are summarized in Table 1. In Examples 1 to 6 and Comparative Examples 3 to 7, 100 parts by weight of petroleum heavy oil or coal tar pitch having different fa values were mixed with 67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluenesulfonic acid. While removing water produced during the reaction, the temperature was raised to 150 ° C., and the reaction was carried out at 150 ° C. for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace, heated to 1100 ° C. at a heating rate of 100 ° C./hour in a nitrogen stream, and when it reached 1100 ° C., it was held for 1 hour, and then the temperature in the furnace was almost the same as room temperature. It was left to cool until. A battery was manufactured using the carbon obtained here, and then the battery was tested.

[0049]

[Table 1] As is clear from Table 1, when the fa value is less than 0.4,
Compared with the results obtained in Comparative Examples 1 and 2, the loss capacity generated in the first cycle is large and the charge / discharge capacity is small, which is not preferable. On the other hand, the batteries of Examples 1 to 6 are Comparative Example 1
The capacity was larger than that of Nos. 1 to 2, and its superiority was confirmed.

Comparative Example 8 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
5 parts by weight of formalin (37% formaldehyde) ([weight of formaldehyde in formalin] / [weight of heavy oils or pitches] = 0.02), 20 parts by weight of paratoluenesulfonic acid are mixed with While removing water produced during the reaction, the temperature was raised to 150 ° C., and the reaction was carried out at 150 ° C. for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. 100 more of this precipitate
It was poured into 0 part by weight of toluene and precipitated to obtain a resin. This resin was placed in an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen stream, and then heated to 1100 ° C.
After reaching the temperature for 1 hour, the temperature was maintained for 1 hour and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 9 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
11 parts by weight of formalin (37% formaldehyde) ([weight of formaldehyde in formalin] /
[Weight of heavy oils or pitches] = 0.04) and 20 parts by weight of paratoluene sulfonic acid are mixed, the temperature is raised to 150 ° C. while removing water generated during the reaction, and the reaction is carried out at 150 ° C. for 2 hours. Let The reaction mixture was added with 1000 parts by weight of n-
Poured into hexane and precipitated. 1 more of this precipitate
It was poured into 000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen gas stream,
When the temperature reached ℃, it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 7 The bottom oil obtained by fluid catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
13 parts by weight of formalin (37% formaldehyde) ([weight of formaldehyde in formalin] /
[Weight of heavy oils or pitches] = 0.05), 20 parts by weight of paratoluene sulfonic acid are mixed, the temperature is raised to 150 ° C. while removing water generated during the reaction, and the reaction is carried out at 150 ° C. for 2 hours. Let The reaction mixture was added with 1000 parts by weight of n-
Poured into hexane and precipitated. 1 more of this precipitate
It was poured into 000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen gas stream,
When the temperature reached ℃, it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 8 The bottom oil obtained by the fluid catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
Formalin (37% formaldehyde) 108 in parts by weight
Parts by weight ([weight of formaldehyde in formalin] /
[Weight of heavy oils or pitches] = 0.4), 20 parts by weight of paratoluene sulfonic acid are mixed, the temperature is raised to 150 ° C. while removing water produced during the reaction, and the reaction is carried out at 150 ° C. for 2 hours. Let The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. 10 more of this precipitate
It was poured into 00 parts by weight of toluene and precipitated to obtain a resin. This resin was placed in an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen stream, and then heated to 1100 ° C.
After reaching the temperature for 1 hour, the temperature was maintained for 1 hour and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 10 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
135 parts by weight of formalin (37% formaldehyde)
Parts by weight ([weight of formaldehyde in formalin] /
[Weight of heavy oils or pitches] = 0.5), 20 parts by weight of paratoluenesulfonic acid are mixed, the temperature is raised to 150 ° C. while removing water produced during the reaction, and the reaction is carried out at 150 ° C. for 2 hours. Let The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. 10 more of this precipitate
It was poured into 00 parts by weight of toluene and precipitated to obtain a resin. This resin was placed in an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen stream, and then heated to 1100 ° C.
After reaching the temperature for 1 hour, the temperature was maintained for 1 hour and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 11 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
216 parts by weight formalin (37% formaldehyde)
Parts by weight ([weight of formaldehyde in formalin] /
[Weight of heavy oils or pitches] = 0.8), 20 parts by weight of paratoluene sulfonic acid are mixed, heated to 150 ° C. while removing water produced during the reaction, and reacted at 150 ° C. for 2 hours Let The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. 10 more of this precipitate
It was poured into 00 parts by weight of toluene and precipitated to obtain a resin. This resin was placed in an electric furnace and heated to 1100 ° C. at a temperature rising rate of 100 ° C./hour in a nitrogen stream, and then heated to 1100 ° C.
After reaching the temperature for 1 hour, the temperature was maintained for 1 hour and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

The above results are summarized in Table 1. Examples 7 to 8 and Example 3 and Comparative Examples 8 to 11 have fa values of 0.7.
100 parts by weight of petroleum-based heavy oil, mixed with various ratios of formalin (37% formaldehyde) and 20 parts by weight of paratoluenesulfonic acid, and heated to 150 ° C. while removing water generated during the reaction, to 150 ° C. And reacted for 2 hours.
The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin was put into an electric furnace, heated to 1100 ° C. at a heating rate of 100 ° C./hour in a nitrogen stream, and when it reached 1100 ° C., it was held for 1 hour, and then the temperature in the furnace was almost the same as room temperature. It was left to cool until. A battery was manufactured using the carbon obtained here, and then the battery was tested.

As is clear from Table 1, when ([weight of formaldehyde in formalin] / [weight of heavy oils or pitches]) is 0.4 or more, the results were obtained in Comparative Examples 1 and 2. Compared with the results, the loss capacity generated in the first cycle is large and the charge / discharge capacity is small, which is not preferable. Further, when it is 0.05 or less, there is no superiority as compared with the result of Comparative Example 1, which is not preferable. On the other hand, Examples 7 to
The batteries of Example 8 and Example 3 had larger capacities than those of Comparative Examples 1 and 2, and their superiority was confirmed.

Comparative Example 12 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was put into an electric furnace as it was, heated to 1100 ° C. at a heating rate in a nitrogen stream of 100 ° C./hour, and when it reached 1100 ° C., 1
After holding for a period of time, the temperature inside the furnace was allowed to cool until it became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 12 is the case where the solvent extraction operation was not performed, but it is not preferable because the capacity is smaller than that in Example 3 and the loss capacity generated in the first cycle is large.

Comparative Example 13 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
The temperature is raised to 700 ° C at a heating rate in a nitrogen stream of ° C / hour,
After the temperature reached 700 ° C., the temperature was maintained for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 14 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
At a heating rate of 800 ° C in a nitrogen stream of ° C / hour,
When the temperature reached 800 ° C., it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 9 The bottom oil obtained by the fluid catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
At a heating rate of 900 ° C / hour in a nitrogen stream,
When the temperature reached 900 ° C., it was held for 1 hour, and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Example 10 The bottom oil obtained by fluid catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
The temperature was raised to 1300 ° C. at a temperature rising rate in a nitrogen gas flow rate of ° C./hour, and when the temperature reached 1300 ° C., the temperature was held for 1 hour and then allowed to cool until the temperature in the furnace became almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 15 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
The temperature was raised to 1400 ° C. in a nitrogen stream at a temperature of ° C./hour, and when the temperature reached 1400 ° C., the temperature was maintained for 1 hour and then allowed to cool until the temperature in the furnace was almost the same as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

Comparative Example 16 The bottom oil obtained by fluidized catalytic cracking of vacuum gas oil was distilled to obtain a heavy oil having an fa value of 0.7. This raw material 100
67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid are mixed in parts by weight, and the temperature is raised to 150 ° C. while removing water generated during the reaction,
The reaction was carried out at 150 ° C for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. This precipitate was further poured into 1000 parts by weight of toluene and precipitated to obtain a resin. This resin is put into an electric furnace and
The temperature was raised to 1700 ° C. at a temperature rising rate in a nitrogen stream of ° C./hour, and when the temperature reached 1700 ° C., the temperature was maintained for 1 hour, and then the temperature in the furnace was allowed to cool to almost the same temperature as room temperature. A battery was manufactured using the carbon obtained here, and then the battery was tested. The method of testing and producing the battery is as described above.

The above results are summarized in Table 1. Examples 9 to 10 and Example 3 and Comparative Examples 13 to 16 have fa values =
Mix 100 parts by weight of heavy petroleum oil of 0.7 with 67 parts by weight of formalin (37% formaldehyde) and 20 parts by weight of paratoluene sulfonic acid up to 150 ° C while removing water generated during the reaction. The temperature was raised and the reaction was carried out at 150 ° C. for 2 hours. The reaction mixture was poured into 1000 parts by weight of n-hexane to cause precipitation. 10 more of this precipitate
It was poured into 00 parts by weight of toluene and precipitated to obtain a resin. This resin was placed in an electric furnace, heated to various temperatures at a heating rate of 100 ° C./hour in a nitrogen stream, and held at that temperature for 1 hour. Let it cool until it became the same. A battery was manufactured using the carbon obtained here, and then the battery was tested.

As is clear from Table 1, the carbonization temperature is 9
When the temperature is lower than 00 ° C., the capacity obtained at the beginning of the cycle is large, but the capacity decreases with each cycle, and the capacity retention ratio is extremely inferior to Comparative Examples 1 and 2, which is not preferable.
When the carbon temperature exceeds 1300 ° C., the cycle characteristics are extremely good, but the charge / discharge capacity is unfavorably smaller than the capacity of the batteries obtained in Comparative Examples 1 and 2.
On the other hand, the batteries of Examples 9 to 10 and Example 3 are Comparative Examples 1 and 2.
The capacity was larger than that of, and its superiority was confirmed.

Although the spiral rechargeable lithium secondary battery has been described in the above embodiments, the present invention is not limited to this structure, and for example, flat or prismatic rechargeable lithium batteries. The present invention can also be applied to.

[0069]

As described above, according to the present invention, although the amount of unorganized carbon in the carbonaceous material is small and most of the carbonaceous material is composed of a 6-membered ring, the conventional graphitizable carbon ( For example, the average interplanar spacing between the carbon six-membered ring network planes is much wider than that of coke), so there are many sites where lithium is occluded and the capacity is large, and in the solid phase of the carbonaceous material. Since the lithium diffusion rate is fast and the heavy load discharge characteristics are excellent, it is possible to provide a lithium secondary battery having a large capacity and excellent capacity stability during charge / discharge cycles, and its industrial value is Is large.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a lithium secondary battery.

Front Page Continuation (72) Inventor Hidetetsu Nagura 5 36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd.

Claims (2)

[Claims] 1. A negative electrode carbonaceous material used in a lithium secondary battery comprising a positive electrode containing lithium and a non-aqueous electrolyte, wherein an aromatic hydrocarbon fraction fa value is 0.40 to 0.95. A pitch and formalin are mixed in the presence of an acid catalyst so that the weight ratio of formaldehyde in the formalin to the pitch is 0.05 to 0.4, and the mixture is heated and reacted,
The n-hexane and toluene-soluble components were removed, and the obtained resinous polymer compound reached a maximum reaching temperature of 900 to 13
A negative electrode carbonaceous material for a lithium secondary battery, which is carbonized at 00 ° C. 2. A method for producing a negative electrode carbonaceous material used in a lithium secondary battery comprising a positive electrode containing lithium and a non-aqueous electrolyte, wherein an aromatic hydrocarbon fraction fa value is 0.40 to 0. 0.95 pitch and formalin are mixed in the presence of an acid catalyst so that the weight ratio of formaldehyde in the formalin to the pitch is 0.05 to 0.4, followed by heating reaction and then n-hexane. And the components soluble in toluene are removed, and the obtained resinous polymer compound is allowed to reach the maximum temperature of 900-1.
A method for producing a negative electrode carbonaceous material for a lithium secondary battery, which comprises carbonizing at 300 ° C.