JPH09241527A - Production of carbonaceous material and production of carbonaceous cathode material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the irreversible capacity of the first cycle of charge and discharge of a nonaq. electrolyte secondary battery. SOLUTION: This carbonaceous cathode material is produced from a cabon black having such characteristics that the spacing d002 of the 002 plane measured by wide-angle X-ray diffractometry is 3.553.70Å; that the DBP absorption is 50-200ml/100g; and the nitrogen adsorption specific surface area measured by the BET method is 30-300m<2> /g. The carbon black is subjected to polymn. at 40-100 deg.C in a solvent contg. a polymn. initiator selected from among azobisisoblutyronitrile, benzoyl peroxide, lauroyl peroxide, ammonium peroxodisulfate, and potassium peroxodisulfate or polymn. at -10 to 40 deg.C in the presence of a reducing agent and then to washing and extraction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbonaceous material and a method for producing a carbonaceous material for a negative electrode which can be used in a non-aqueous electrolyte secondary battery and can occlude and release lithium.

[0002]

2. Description of the Related Art A non-aqueous electrolyte secondary battery using a carbonaceous material as a negative electrode has been attracting attention because it exhibits excellent durability with little capacity deterioration during charge and discharge cycles. This is because the negative electrode carbonaceous material can reversibly occlude and release lithium at a base potential, and the fact that the intercalation compound between lithium and the negative electrode carbonaceous material is reversibly formed is utilized. ing.

For example, when a secondary battery is constituted by a positive electrode containing a sufficient amount of lithium, a negative electrode carbonaceous material, and a non-aqueous lithium ion conductive electrolyte via a separator, the secondary battery is discharged. Assembly will be completed. For this reason, this type of battery cannot be in a dischargeable state unless it is charged after assembly. First for this secondary battery
When charging is performed in the cycle, lithium in the positive electrode is electrochemically doped between the layers of the negative electrode carbonaceous material. Then, when discharged, the doped lithium is dedoped,
Return to the positive electrode again.

By the way, since the electric capacity (mAh / g) per unit weight of the negative electrode carbonaceous material in this case is determined by the capacity capable of storing and releasing lithium, in such a negative electrode the lithium electrochemical capacity is increased. It is desirable to increase the specific storage amount as much as possible. When electrochemically producing an intercalation compound of lithium and carbon in a battery like this type of secondary battery, theoretically a state in which one lithium atom is occluded to six carbon atoms Is the upper limit, that is, the saturated composition of the intercalation compound of lithium and the negative electrode carbonaceous material.

As a negative electrode carbonaceous material satisfying such conditions, a carbonized or graphitized material of a certain organic polymer compound or its composite is used. In addition, naturally occurring carbonaceous substances such as natural graphite have also been investigated.

However, in the case of the negative electrode carbonaceous material obtained by the above-described manufacturing method, the operation is particularly performed when lithium is absorbed and released at a high current density, that is, when it is incorporated as a secondary battery. Each of them corresponds to quick charge and heavy load discharge, but the amount that can store and release lithium, that is, the capacity when a secondary battery is configured is insufficient,
The actual situation is that the amount is only about half of the theoretical value of the electrochemically reversible storage amount.

Although the degree of difference depends on the type of electrolyte, the dedoping amount was not 100% of the lithium doping amount in the first cycle. It is considered that this is because a part of the doped lithium is inactivated and remains in the negative electrode carbonaceous material.

Furthermore, when a non-aqueous electrolyte is used as the non-aqueous lithium ion conductive electrolyte, in addition to the above-described inactivation of lithium, lithium is doped during the charging process and, at the same time, this electrochemical reaction occurs. It is possible that part of the lithium involved is consumed for the reductive decomposition of the non-aqueous electrolyte. Therefore, the charge and discharge are repeated with the capacity reduced in all the subsequent cycles.

On the other hand, since the charge / discharge reaction is carried out by moving lithium ions from the positive electrode side to the negative electrode side and 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, since the amount that can be moved during de-doping in the first cycle is reduced, charge and discharge are repeated with the capacity reduced in all subsequent cycles, which causes a problem that the energy density of the battery decreases. .

Therefore, a negative electrode carbonaceous material developed by the present inventors to solve such a problem is disclosed in Japanese Patent Laid-Open No. 6-
No. 187989, carbon black obtained by an oil furnace method using creosote oil as a raw material is used as a carbonaceous material, and the carbonaceous material has physical property values shown in (A) to (C) below. Have all.

(A) The interplanar spacing d (002) of the 002 plane measured by the X-ray wide angle analysis method is 3.55 to 3.70.
(Angstrom), crystallite size Lc in the c-axis direction
Is 10 to 20 (angstrom). (B) DBP oil absorption is 50 to 200 ml / 100 g (D
BP). (C) The nitrogen adsorption specific surface area determined by the BET method is 30.
~ 300 m ² / g.

When such a carbonaceous material made of carbon black is used in a non-aqueous electrolyte secondary battery, the capacity for storing and releasing lithium is large and the cycle stability can be extremely improved.

[0013]

However, in the non-aqueous electrolyte secondary battery using the carbonaceous material described above,
The irreversible capacity in the first cycle of charging / discharging cannot be ignored, and improvement has been desired. Therefore, as a result of intensive investigations by the present inventors to establish a method for reducing such irreversible capacity by a relatively simple operation, a part of the irreversible capacity is caused by free radicals present on the surface of carbon black. I came to the conclusion that Then, the free radicals can be removed from the carbon black by capturing the free radicals by heating the carbon black having the surface present in the solvent in which the polymerization initiator is present,
It has been found that if this carbon black is used as a negative electrode carbonaceous material of a non-aqueous electrolyte secondary battery, the irreversible capacity of the first cycle during charge / discharge can be significantly reduced.

The present invention has been made based on such a background, and an object thereof is to provide a method for producing a carbonaceous material which removes or inactivates free radicals existing on the surface of the carbonaceous material, and When used as the negative electrode of a non-aqueous electrolyte secondary battery, its irreversible capacity can be significantly reduced, and the discharge capacity of the battery can be improved, and the negative electrode carbonaceous material for a non-aqueous electrolyte secondary battery It is to provide a manufacturing method of.

[0015]

In the production method of the present invention according to claim 1, a carbonaceous material composed of carbon black having free radicals on its surface is polymerized in a solvent containing a polymerization initiator. By doing so, the free radicals are removed or inactivated.

In the manufacturing method of the present invention according to claim 2, it is used as a negative electrode for a non-aqueous electrolyte secondary battery, capable of inserting and extracting lithium, and measured by X-ray wide-angle diffraction method. The surface spacing d002 is 3.55 to 3.
70 (angstrom), the size Lc of the crystal lattice in the C-axis direction is 10-20 (angstrom), the DBP oil absorption is 50-200 ml / 100 g,
And the nitrogen adsorption specific surface area determined by the BET method is 30 to
A method for producing a carbonaceous material comprising carbon black having all physical properties of 300 m ² / g, wherein the carbonaceous material is azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, ammonium peroxodisulfate, Or in a solvent in the presence of one polymerization initiator selected from the group consisting of potassium peroxodisulfate
After the polymerization reaction in the temperature range of 100 ° C., the washing and extraction treatments are carried out.

In the manufacturing method of the present invention according to claim 3, it is used as a negative electrode for a non-aqueous electrolyte secondary battery, capable of inserting and extracting lithium, and measured by an X-ray wide-angle diffraction method. The surface spacing d002 is 3.55 to 3.
70 (angstrom), the size Lc of the crystal lattice in the C-axis direction is 10-20 (angstrom), the DBP oil absorption is 50-200 ml / 100 g,
And the nitrogen adsorption specific surface area determined by the BET method is 30 to
A method for producing a carbonaceous material composed of carbon black having all physical properties of 300 m ² / g, wherein the carbonaceous material is prepared from benzoyl peroxide, lauroyl peroxide, potassium peroxodisulfate, or ammonium peroxodisulfate. A polymerization reaction is carried out in a temperature range of -10 ° C to 40 ° C in a solvent containing one polymerization initiator and a reducing agent selected from the group, followed by washing and extraction.

In the present invention having the above-mentioned constitution, free radicals existing on the surface of carbon black as a carbonaceous material are polymerized with polymerization initiator radicals produced by heating or reducing the polymerization initiator. By reacting, free radicals on the surface of carbon black are trapped and removed or inactivated.

When carbon black from which free radicals have been removed is used as the negative electrode carbonaceous material of a non-aqueous electrolyte secondary battery, the irreversible capacity of the first cycle during its charge / discharge is significantly reduced.

The polymerization reaction will be specifically described. The polymerization initiator used in the present invention can be classified into two types, a peroxide and an azo compound. As the peroxide, potassium peroxodisulfate, ammonium peroxodisulfate, benzoyl peroxide, lauroyl peroxide,
The azo compound is azobisisobutyronitrile, but these polymerization initiators generate free radicals as shown by the following formula by heat treatment and are trapped on the carbon black surface.

In the case of peroxide

Embedded image For azo compounds

Embedded image As the carbon black used in the production method of the present invention, for example, one obtained by an oil furnace method using creosote oil as a raw material is used.

The physical property values of (A) to (C) will be described. The interplanar spacing d002 of the 002 planes of each carbon black and the size Lc of the crystal lattice in the C-axis direction are X according to the Gakshin method. It is obtained by the wide-angle diffraction method,
The DBP oil absorption is 70, which is the maximum torque when DBP is added to carbon black using an absorber meter.
%, And the nitrogen adsorption specific surface area is determined by the BET method.

Next, the carbon black having the above physical properties (A) to (C) is treated in a solvent containing the polymerization initiator (D) or (E), and then washed and extracted. The detailed means will be described.

First, as the reaction vessel used in the present invention, a pressure-resistant glass bottle, a laminated pressure-resistant glass tube, and various brim-stopping pressure-resistant glass vessels are used. Any material that is devised so as to withstand pressure, such as a clasp stopper, a screw cap, or a cock stopper, is sufficient, but a glass ampoule for a sealed tube is preferable because it can be sealed by a vacuum line. Further, when a large amount of carbon black is polymerized, a flask container with a stirring rod having good airtightness is suitable.

As the reaction apparatus used for the heat treatment, a conventional apparatus for radical polymerization can be used. A heating and thermostating device is generally attached to such a device, and the temperature is controlled in the thermostat by agitating or circulating a liquid in a thermostatic bath such as air, water, liquid paraffin, or silicone oil. At this time, a shaking device may be used together to further accelerate the polymerization reaction. As the shaking device, there are a rotary type, a vertical shaking type, a left and right shaking type, a seesaw type, etc., and a reaction vessel may be fixed to these to carry out a polymerization reaction.

The solvent used in the polymerization reaction may be appropriately selected according to the polymerization initiator. In the polymerization initiator used in the present invention, potassium peroxodisulfate and ammonium peroxodisulfate are water-soluble, and benzoyl peroxide is used. , Lauroyl peroxide, and azobisisobutyronitrile are oil-soluble. In the case of water solubility, distilled water is mainly used as a solvent without any problem, and in the case of oil solubility, benzene, toluene, ethyl acetate, methanol, dimethylformamide or the like can be used.

The polymerization initiator may be purified, if necessary, and is generally distilled in a nitrogen stream, or recrystallized or reprecipitated. For example, in the case of purifying benzoyl peroxide which is one of the polymerization initiators used in the present invention, it is recrystallized from chloroform or benzene, or
Purify by the reprecipitation method in which methanol is added to the chloroform solution. The generated precipitate may be dried under reduced pressure on calcium chloride. In the case of azobisisobutyronitrile, it may be recrystallized from ethanol or methanol, and the obtained crystal may be dried under reduced pressure.

Further, among the polymerization initiators according to the present invention, in the case of peroxides, that is, potassium peroxodisulfate, ammonium peroxodisulfate, benzoyl peroxide and lauroyl peroxide, redox polymerization is initiated in the presence of a suitable reducing agent. It acts as an agent and can generate a polymerization initiator radical at a low temperature of 40 ° C. or lower.

As the reducing agent used in this case, sodium sulfite, sodium hydrogen sulfite, triethanolamine or the like is used in the case of a water-soluble polymerization initiator, and dimethylaniline or naphthenic acid is used in the case of an oil-soluble polymerization initiator. Cobalt, sulfinic acid, mercaptan, etc. can be used. Even with such a method, it is possible to cause a free radical existing on the surface of carbon black and a polymerization initiator radical generated by the heat treatment to undergo a polymerization reaction.

Other combinations of polymerization initiator and reducing agent include hydrogen peroxide and iron (II) salts, cumene hydroperoxide and iron (II) salts, peroxides (hydrogen peroxide, hydroxyperoxide) and organic metals. Examples thereof include alkyl (triethylaluminum, triethylboron, diethylzinc) and the like. However, in the case of carrying out the polymerization reaction with such a combination of the polymerization initiator and the reducing agent, by maintaining an extremely low temperature of -10 ° C or lower, it is possible to stably act as a polymerization initiator radical as a redox polymerization initiator. However, in this extremely low temperature state, the polymerization reaction with the free radicals on the surface of carbon black becomes poor, so some improvement is required.

Other polymerization initiators outside the scope of the invention include cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide and the like. Is generally called a high temperature initiator, and usually requires a high temperature condition of 100 ° C. or higher. Therefore, when using these, attach a metal lid to the reactor, enclose it with a partition made of concrete, iron plate, wood, or plastic, put the reaction container in a metal tube or wrap it with a wire mesh. Then, cloth may be wrapped, but since such a work is complicated, some improvement is required.

Therefore, the polymerization initiator used in the present invention is preferably as described above. The heat treatment temperature in the case where this polymerization initiator undergoes a polymerization reaction with carbon black in a solvent will be explained. In the present invention according to claim 2, potassium peroxodisulfate, ammonium peroxodisulfate, benzoyl peroxide, and peroxide are described. Since one type of polymerization initiator selected from the group consisting of lauroyl and azobisisobutyronitrile is used, 40 ° C to 1
It can be set appropriately within the temperature range of 00 ° C. When the temperature is lower than 40 ° C., it becomes difficult for the polymerization reaction to proceed as described above, and if the polymerization reaction is attempted to be performed to such an extent that the effect of the present invention can be confirmed, a considerable time is consumed, which is preferable. Absent. Also, if the polymerization reaction is attempted to be carried out at 100 ° C. or higher, the radicals of the polymerization initiator become unstable, causing a problem in safety in the manufacturing process as described above, and the quality of the polymerization reaction is stabilized because the polymerization reaction progresses rapidly. It is difficult and not preferable. At this time, in order to stabilize the reaction product, this reaction is preferably carried out in a constant temperature state.

In the present invention according to claim 3, one kind selected from the group consisting of potassium peroxodisulfate, ammonium peroxodisulfate, benzoyl peroxide and lauroyl peroxide in the presence of the above-mentioned reducing agent. When the above polymerization initiator is used, it can be appropriately set within a temperature range of -10 ° C to 40 ° C. When the temperature is higher than 40 ° C, the polymerization initiator does not act stably as a redox polymerization initiator radical, which is not preferable. Also, -10 ℃
When it is lower than the above range, the polymerization reaction becomes difficult to proceed as described above, which is not preferable. At this time, as described above, this polymerization reaction is preferably carried out in a constant temperature state.

The concentration of the polymerization initiator in the solvent and the reaction time may be appropriately set, but it is preferable that the concentration of the polymerization initiator is high and the reaction time is long so that the polymerization reaction is sufficiently carried out. However, even when the concentration of the polymerization initiator is low and the polymerization reaction is short, the carbon black is subjected to heat treatment in a solvent in which the polymerization initiator is present, and free radicals present on the surface of the carbon black and the polymerization initiation generated by the heat treatment are initiated. It is possible to polymerize the agent radicals, which can remove free radicals from the carbon black.

Further, it is necessary to remove the reaction product obtained by such a polymerization reaction and the polymerization initiator not captured on the surface of carbon black. As the method, Soxhlet extraction is the simplest and the most efficient. However, various methods can be used as long as they are similar cleaning and removing methods. The solvent used at this time may be the same solvent used in the polymerization reaction.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Referring to Table 1 and FIG. 1 below,
Embodiments of the present invention will be described in detail with reference to Comparative Examples 1 to 3 and Examples 1 to 9.

Comparative Example 1 Commercially available petroleum coke was used as a negative electrode carbonaceous material without any special treatment.

Comparative Example 2 Commercially available scaly natural graphite from China was used as a negative electrode carbonaceous material without any special treatment.

[Comparative Example 3] Physical property values (A) to
The carbon black having (C) was used as a negative electrode carbonaceous material without any special treatment.

[Example 1] In a separable flask equipped with a stirring rod and having an internal volume of 3 l, 60 g of azobisisobutyronitrile was used as a polymerization initiator, and the physical properties (A) to (C) described above were used.
1 g of carbon black having the above and 2 l of toluene were put therein, and the mixture was sealed, and a nitrogen gas was made to flow. While maintaining this state, the mixture was placed in a constant temperature bath at 60 ° C., and a polymerization reaction was carried out for 8 hours while stirring with a stirring rod. After that, the reacted carbon black is taken out, toluene is refluxed with a Soxhlet extractor to wash the carbon black, unreacted azobisisobutyronitrile is removed, and dried under reduced pressure at 60 ° C. Black was made.

[Example 2] In Example 1, the same amount of benzoyl peroxide was used instead of azobisisobutyronitrile as a polymerization initiator, and the other conditions were the same.

[Example 3] In Example 1, the same amount of lauroyl peroxide was used in place of azobisisobutyronitrile as a polymerization initiator, and other conditions were the same.

[Example 4] In Example 1, the same amount of potassium peroxodisulfate was used in place of azobisisobutyronitrile as a polymerization initiator, and the other conditions were the same.

[Example 5] In Example 1, the same amount of ammonium peroxodisulfate was used in place of azobisisobutyronitrile as a polymerization initiator, and other conditions were the same.

Example 6 In a separable flask equipped with a stirring rod and having an internal volume of 3 l, 60 g of benzoyl peroxide as a polymerization initiator, 20 g of dimethylaniline as a reducing agent, and the above-mentioned physical properties (A) to (C) were used. Carbon black (1 g) and toluene (2 l) were put therein, the well was sealed, and a nitrogen gas was made to flow. While maintaining this state, the mixture was placed in a constant temperature bath at 35 ° C., and a polymerization reaction was carried out for 8 hours while stirring with a stirring rod. After that, the reacted carbon black is taken out, toluene is refluxed with a Soxhlet extractor to wash the carbon black, unreacted benzoyl peroxide is removed, and dried under reduced pressure at 60 ° C. to produce carbon black as a carbonaceous material. did.

[Example 7] In Example 6, the same amount of lauroyl peroxide was used instead of benzoyl peroxide as a polymerization initiator, and other conditions were the same.

[Example 8] In Example 6, the same amount of potassium peroxodisulfate was used instead of benzoyl peroxide as a polymerization initiator, and the same amount of sodium hydrogen sulfite was used instead of dimethylaniline as a reducing agent. The others were the same.

[Example 9] In Example 6, the same amount of ammonium peroxodisulfate was used instead of benzoyl peroxide as a polymerization initiator, and the same amount of sodium hydrogen sulfite was used instead of dimethylaniline as a reducing agent. , And others were the same.

Comparative Examples 1 to 3 and Examples 1 to 1 described above
A spiral type non-aqueous electrolyte secondary battery using the carbon black obtained in No. 9 as a negative electrode carbonaceous material was produced as follows. As shown in the longitudinal sectional view of FIG. 1, this battery has the same structure as the conventional one, and has a spiral shape in which a separator 3 made of a polypropylene porous film is sandwiched between a strip-shaped positive electrode 1 and a negative electrode 2, respectively. Winding to form a winding element. A positive electrode lead plate 5 and a negative electrode lead plate are connected to the positive electrode 1 side and the negative electrode 2 side of this winding element, respectively. In the state where these lead plates 5 are projected upward, the winding element is provided with a cylindrical case 4 having a bottom through a polypropylene insulating plate 12.
Fit inside. Then, the negative electrode lead is connected to the center of the inner bottom surface of the case 4 by spot welding, and the positive electrode lead plate 5 is spot welded to the bottom of the positive electrode terminal plate 7 with a safety valve. Then, after injecting the non-aqueous electrolyte into the case 4,
The positive electrode terminal plate 7 is fitted into the opening of the case 4 via the sealing gasket 8 and caulked to form a spiral non-aqueous electrolyte secondary battery.

In the positive electrode 1, LiCoO _{2 as} a positive electrode active material and an aqueous dispersion of PTFE as a carbon powder binder as a conductive material were mixed at a weight ratio of 100: 10: 10,
A strip-shaped positive electrode sheet was prepared by kneading in a paste form with water and applying it to both surfaces of an aluminum foil having a thickness of 30 μm, followed by drying, rolling and cutting into a predetermined size. 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. As the active material, LiCoO ₂ was used in which cobalt oxide (CoO) and lithium carbonate (Li ₂ CO ₃ ) were mixed at a molar ratio of 2: 1 and heated in air at 900 ° C. for 9 hours. Of the mixing ratios of the above materials, P
The proportion of the aqueous dispersion of TFE is the proportion of solids therein.

As the positive electrode active material, various materials other than those described above can be applied as long as they can be used in this type of battery,
It is particularly preferable to use a material containing a sufficient amount of lithium. For example, LiMn ₂ O ₄ and the general formula LiMO ₂ (where M represents at least one of Co and Ni.
For example, a composite metal oxide represented by LiCoO ₂ or LiCo _0.8 Ni _0.2 O ₂ ) or an intercalation compound containing lithium is suitable.

The negative electrode 2 is made of the powder as a negative electrode carbonaceous material obtained by the above-described production method of the present invention and the binder P.
By mixing an aqueous dispersion of TFE kneaded at a weight ratio of 100: 5 into a nickel expanded metal under pressure, drying and cutting into a predetermined size,
The strip-shaped negative electrode sheet was used. A part of this sheet was scraped off perpendicularly to the longitudinal direction of the sheet, and a nickel negative electrode lead plate was attached by spot welding on a current collector. The ratio of PTFE is the ratio of solid content as above.

As the negative electrode carbonaceous material, the carbon blacks obtained in the above-mentioned Comparative Examples 1 to 3 and Examples 1 to 9 were used.

The non-aqueous electrolytic solution 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, as the organic solvent, propylene carbonate, ethylene carbonate, 1,2-
Examples thereof include dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether and sulfolane. LiCiO ₄ , LiAs as the electrolyte
F ₆ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , L
iCl and the like.

In order to confirm the performance of the spiral type non-aqueous electrolyte secondary battery produced as described above, the charge / discharge cycle characteristics of each of Examples 1 to 9 and Comparative Examples 1 to 3 were measured.

As a measuring method, in the first cycle, the battery was charged to 4.2 V with a constant current of 300 (mA),
When the battery voltage reached 4.2V, charging was performed at a constant voltage so that the battery voltage was kept at 4.2V. The 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) discharge until the battery voltage reached 2.8V. After the second cycle, the charging / discharging cycle was repeated by the same charging / discharging method as in the first cycle, and charging / discharging was performed up to the 100th cycle.

Table 1 shows the measurement results described above.

[0058]

[Table 1] As is clear from comparison between Comparative Example 3 and Examples 1 to 9, the batteries produced in Examples 1 to 9 have a small irreversible capacity generated in the first cycle and a large capacity.
Further, comparing the capacities obtained in the first cycle and the capacities obtained in the 100th cycle, it is extremely excellent as in the battery of Comparative Example 3 in which no special treatment is performed.

Comparing Examples 1 to 9 with Comparative Examples 1 and 2, the capacities were larger than those of natural graphite and petroleum coke used in the conventional battery of this type, and the capacity stability with charge / discharge cycles was high. It turns out that they are equivalent.

The present invention is not limited to the spiral type non-aqueous electrolyte secondary battery described above, but can be applied to various types of lithium secondary batteries such as flat type and prismatic type.

[0061]

As described above in detail, according to the present invention, the free radicals present on the surface of carbon black as the carbonaceous material and the polymerization initiator radicals generated from the polymerization initiator are polymerized. , The free radicals on the surface of carbon black can be captured and removed or inactivated.

When carbon black from which free radicals have been removed is washed and extracted and used as a negative electrode carbonaceous material of a non-aqueous electrolyte secondary battery, the first charge / discharge step is performed.
The irreversible capacity of the cycle can be significantly reduced,
The discharge capacity of the battery can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a non-aqueous electrolyte secondary battery using the present invention and a conventional negative electrode carbonaceous material.

[Explanation of symbols]

1 Positive electrode 2 Negative electrode 3 Separator 4 Case 5 Positive electrode lead plate 7 Positive electrode terminal plate 8 Sealing gasket 12 Polypropylene insulating plate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiro Harada 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd.

Claims (3)

[Claims] 1. A method for producing a carbonaceous material in which a free radical is removed or inactivated by polymerizing a carbonaceous material composed of carbon black having a free radical on the surface in a solvent containing a polymerization initiator. . 2. It is used as a negative electrode for a non-aqueous electrolyte secondary battery, capable of inserting and extracting lithium, and has an interplanar spacing d002 of 002 planes measured by an X-ray wide-angle diffraction method of 3.
55 to 3.70 (angstrom), the size Lc of the crystal lattice in the C-axis direction is 10 to 20 (angstrom), and the DBP oil absorption is 50 to 200 ml / 100 g.
And a nitrogen adsorption specific surface area determined by the BET method of 30 to 300 m ² / g. Polymerization reaction in a temperature range of 40 ° C to 100 ° C in a solvent in the presence of one polymerization initiator selected from the group consisting of butyronitrile, benzoyl peroxide, lauroyl peroxide, ammonium peroxodisulfate, or potassium peroxodisulfate. A method for producing a negative electrode carbonaceous material for a non-aqueous electrolyte secondary battery, which comprises washing and extracting after the treatment. 3. Used in a negative electrode for a non-aqueous electrolyte secondary battery, capable of inserting and extracting lithium, and having an interplanar spacing d002 of 002 planes measured by an X-ray wide angle diffraction method of 3.
55 to 3.70 (angstrom), the size Lc of the crystal lattice in the C-axis direction is 10 to 20 (angstrom), and the DBP oil absorption is 50 to 200 ml / 100 g.
And a nitrogen adsorption specific surface area determined by the BET method is 30 to 300 m ² / g. -10 ° C to 40 ° C in a solvent in the presence of one polymerization initiator and a reducing agent selected from the group consisting of benzoyl, lauroyl peroxide, potassium peroxodisulfate, or ammonium peroxodisulfate.
The method for producing a negative electrode carbonaceous material for a non-aqueous electrolyte secondary battery, which comprises performing a polymerization reaction in the temperature range described above, followed by washing and extraction treatment.