JPH09283143A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery at a high capacity and having excellent discharging characteristic and rate characteristic by using the electrode material, which is formed by including the conductive filler in a specified carbonaceous material, for a negative electrode. SOLUTION: Organic material such as ethylene heavy end tar to be obtained at the time of decomposition of naphtha is burned at 400-950 deg.C so as to obtain the amorphous carbon at 10<1> -10<7> Ω.cm of volume resistivity, at 1-100m<2> /g of a specific surface area and at 0.05-0.5 of H/C as a carbonaceous material, which can absurd and discharge Li ion, and the conductive filler is contained in this carbonaceous material so as to form the electrode material, and this electrode material is used for the negative electrode. In the electrode material, the carbonaceous material is desirably contained at 85-50 volume weight % and the conductive filler is desirably contained at 15-50 volume weight %. As a conductive filler, one or more is desirably selected among carbon black, graphite powder, carbon fiber and metal powder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithium secondary battery having a high capacity and excellent discharge characteristics and rate characteristics.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of electronic devices, there has been a demand for higher capacity secondary batteries with higher capacity. Therefore, lithium-ion secondary batteries, which have higher energy density than nickel-cadmium and nickel-hydrogen batteries, are attracting attention. As the negative electrode material, it was first attempted to use lithium metal, but during repeated charging and discharging, dendrite-like lithium was deposited and penetrated the separator,
It has been revealed that it may reach the positive electrode and cause a short circuit resulting in an ignition accident. Therefore, at present, attention is paid to the use of a carbon material as a negative electrode material, which allows a nonaqueous solvent to flow in and out between layers during a charge / discharge process and prevent lithium metal precipitation. As the carbon material, JP-A-57-208079 proposes to use graphite having high crystallinity. However, since graphite uses intercalation of lithium ions into the graphite crystal as a principle of charge / discharge, 372 mAh / g calculated from LiC6 which is the maximum lithium-introducing compound at room temperature and pressure.
There is a problem that the above capacity cannot be obtained. In addition, compared with graphite such as polymer carbide, coke, carbon fiber, coal and petroleum pitch calcined product, mesocarbon microbeads, etc., a single phase defined by low crystallinity and specific gravity, Raman spectroscopy, specific surface area and other properties The following carbonaceous materials have been proposed. Amorphous carbon having a low crystallinity is larger than the theoretical capacity of graphite of 372 mAh / g and is particularly expected as a capacity increasing method. However, even in this case, the potential during charging / discharging is higher than that of graphite, and the potential indicated by charging / discharging is not flat and has a large hysteresis, so it is difficult to obtain a potential difference from the positive electrode. As a result, there is a problem that a large capacity and high power battery cannot be obtained. Further, it has been found that the capacity is significantly reduced during rapid charging.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium ion secondary battery which has a flat potential during charge and discharge, is close to the potential of Li / Li +, and is also strong against rapid charge. .

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that when the resistivity of the negative electrode material is high, the cell impedance of the battery is high, and thus the charge / discharge potential is high. It was found that the capacity was decreased during rapid charge / discharge, and it was found that the above problem can be solved by adding a conductive filler to the negative electrode material, and the present invention has been completed. That is, the present invention
The present invention relates to a lithium ion secondary battery, characterized in that a carbonaceous material capable of occluding and releasing metal ions uses an electrode material containing a conductive filler as a negative electrode.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
As the carbonaceous material capable of storing and releasing metal ions used in the present invention, a mixture of a carbonaceous raw material and a specific conductive filler is used as a raw material, and the mixture is carbonized. Since this carbon has a structure in which a conductive material is finely dispersed, it is possible to improve the conductivity of the carbonaceous material,
A carbon electrode material for a lithium ion secondary battery, which has a flat charge / discharge potential and an improved rapid charge / discharge property, can be obtained.

Specifically, specifically, the value of d002, which is the interlayer distance of the carbon crystal obtained by X-ray diffraction, is not less than 3.40 Å and not more than 4.00 Å, or the crystal in the C-axis direction. Child size (Lc.) Is 10Å or more, 5
A carbonaceous material satisfying the values of 0 Å or less, and more preferably, both are mentioned. More preferably, the organic matter is 40
The carbonaceous material has a volume resistivity of 10 ¹ to 10 ⁷ Ω · cm, a BET specific surface area of 1 m ² / g or more and 100 m ² / g or less, H / C (hydrogen). /
Amorphous carbon defined as having a carbon atom abundance ratio of 0.05 or more and 0.5 or less, and more preferably 0.1 or more and 0.3 or less.

Regarding the raw materials for obtaining these carbonaceous materials,
This will be described in detail below. As organic matter in which carbonization proceeds in the liquid phase, coal-based heavy oil such as coal tar pitch from soft pitch to hard pitch and dry-distilled liquefied oil, normal pressure residual oil, direct current heavy oil such as vacuum residual oil, Examples include heavy petroleum-based oils such as crude oil and naphtha, which are by-products of thermal decomposition such as ethylene tar, and heavy oils such as cracked heavy oils.

Further, aromatic hydrocarbons such as acenaphthylene, decacyclene and anthracene, N ring compounds such as phenazine and acridine, S ring compounds such as thiophene,
Although a pressure of 30 MPa or more is required, examples thereof include alicyclic rings such as adamantane, polyphenylene such as biphenyl and terphenyl, and polymers such as polyvinyl chloride and polyvinyl alcohol.

[0009] As an organic substance whose carbonization proceeds in the solid phase,
Examples include natural polymers such as cellulose and saccharides, thermoplastic resins such as polyphenylene sulfide, and polyphenylene oxide; and thermosetting resins such as furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin. A carbonaceous material is obtained by firing the above raw materials at 400 to 950 ° C, and more preferably at 600 to 800 ° C. The carbonaceous matter is preferably 1 to 100 by pulverization.
It is used as particles having an average particle diameter of μm, more preferably 5 to 50 μm.

[0010] As the electrically conductive filler of the present invention has high conductivity than the carbonaceous material, preferably a volume resistivity of less than 10 ¹ Omega · cm, more preferably 10 ^-3 to 10 ⁰
Ω · cm. As the shape of the conductive filler, various shapes such as spherical, plate-like, and fibrous can be used, but as the preferable one, those having an average particle diameter smaller than the crushed particle diameter of the carbonaceous material are preferable, and particularly preferable. Is that the average particle diameter or the average major axis of the conductive filler is in the range of 0.05 to 90% of the average particle diameter of the carbonaceous material capable of storing and releasing the metal ions after firing and crushing.

Examples of the conductive filler include carbon-based filler and metal powder. As the carbon-based filler, one having metal such as nickel attached to the surface and further improved conductivity can also be used. Specific preferred examples of the conductive filler include conductive carbon black such as acetylene black and Ketjen black, artificial graphite (T manufactured by TIMCAL).
6, KS6, SFG6, etc.), graphite powder such as natural graphite (NG2, NG7 etc. manufactured by Kansai Thermo Chemical Co., Inc.), carbon fiber such as vapor grown carbon fiber, metal powder and the like.

Of these, nickel powder, copper powder, and stainless steel powder are preferable as the metal powder in view of the negative electrode potential in the battery. Also, nickel powder has good conductivity,
It is preferable because it is also excellent in oxidation resistance. In particular, carbonyl nickel powder produced by thermal decomposition of nickel tetracarbonyl has high purity, and spherical particles having spike-like protrusions are connected in a filament shape. For,
It is preferable because the particles are excellent in contact with each other and a conductive path is easily formed.

The carbonaceous filler is a carbonaceous material raw material,
Especially excellent compatibility at the raw material mixing stage with heavy oil type raw materials,
It is easy to produce a composite material having a uniform composition. In addition, after firing, it is possible to improve the conductivity of the carbonaceous material and to contribute to the electrode capacity due to the lithium ion storage / release capacity of the filler itself. Generally, when a conductive filler is added to an insulating material or a high resistance material, a so-called percolation phenomenon in which the resistance rapidly decreases at a specific volume fraction is exhibited. Therefore, it is necessary that the ratio of the conductive filler is larger than the percolation threshold value. More specifically, the content of the conductive filler and the carbonaceous material is preferably 85 to 50 Vo in the final adjusted electrode.
l. %, The conductive filler is 15 to 50 Vol. %, More preferably 85 to 65 Vol. %, The conductive filler is 15 to 35 Vol. %.

When the amount of the conductive filler is less than the above range,
There is little improvement in the low potential and rapid charge / discharge characteristics, and if the content is more than the above range, the volume energy density and the weight energy density may decrease. The above range is not the raw material charging ratio but the content at the stage of the final carbonaceous material. Therefore, at the time of charging, it is necessary to determine the blending amount of the raw material in consideration of the composition ratio at the final stage.

Next, a method for manufacturing the electrode of the present invention will be described. The method for producing the electrode of the present invention is not particularly limited as long as the carbonaceous material raw material and the conductive filler are used as the above-mentioned raw materials, and conventionally known methods can be adopted. For example, a carbonaceous material raw material and a conductive filler are mixed with a mixer having a heating means at a charging ratio such that the final composition is within the above range, and detarring treatment is performed, 400 to 950 ° C., 0.1 to 5 hours, Preferably, the baking is performed at 600 to 800 ° C. for 0.5 to 3 hours. The calcined product is crushed to preferably 1 to 100 μm, more preferably 5 to 50 μm in average particle size, and a binder, a solvent and the like are added to the crushed product to form a slurry, which is made of metal such as copper foil. An electrode is formed by applying and drying the slurry on the substrate of the current collector. Further, the electrode material is directly roll-formed,
It is also possible to form the shape of the electrode by a method such as compression molding.

Binders that can be used for the above purposes include
Solvent stable polyethylene, polypropylene,
Resin-based polymers such as polyethylene terephthalate, aromatic polyamide, cellulose, styrene-butadiene rubber,
Thermoplastics such as isoprene rubber, butadiene rubber, rubber-like polymers such as ethylene / propylene rubber, styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / isoprene / styrene block copolymers, hydrogenated products thereof, etc. Elastomeric polymers, syndiotactic 12-polybutadiene, ethylene / vinyl acetate copolymers, propylene / α-olefin (C2-12) copolymers and other soft resinous polymers, polyvinylidene fluoride,
Examples thereof include fluoropolymers such as polytetrafluoroethylene and polytetrafluoroethylene / ethylene copolymers, and polymer compositions having ion conductivity of alkali metal ions, particularly lithium ions.

Examples of the above-mentioned polymer having ion conductivity include polyether polymer compounds such as polyethylene oxide and polypropylene oxide, cross-linked polymer of polyether compounds, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, Polyvinylidene carbonate, a polymer compound such as polyacrylonitrile, a lithium salt, or a system in which an alkali metal salt mainly composed of lithium is combined, or a high dielectric constant of propylene carbonate, ethylene carbonate, γ-butyrolactone, etc. It is possible to use a system in which the organic compound has. The ionic conductivity of such an ion conductive polymer composition at room temperature is preferably 10 ⁻⁵ S / cm.
Or more, more preferably 10 ⁻³ S / cm or more.

The carbonaceous material used in the present invention and the above-mentioned binder may be mixed in various forms.
That is, a form in which both particles are mixed, a form in which a fibrous binder is mixed with particles of a carbonaceous material so as to be entangled with each other, or a form in which a layer of the binder is attached to the surface of the particles of the carbonaceous material can be mentioned. The mixing ratio of the carbonaceous material and the binder is preferably 0.1 to 30% by weight, more preferably 0.5 to 10% by weight, based on the carbonaceous material. If the binder is added in an amount more than this, the internal resistance of the electrode increases, which is not preferable, and if the amount is less than this, the binding property between the current collector and the carbonaceous powder is poor.

The negative electrode plate thus produced and the electrolytic solution and the positive electrode plate described below are combined with other battery components such as a separator, a gasket, a current collector, a sealing plate, and a cell case to form a secondary battery. . Batteries that can be created are not particularly limited to cylinder type, square type, coin type, etc.,
Basically, a current collector and a negative electrode material are placed on a cell floor plate, an electrolyte solution and a separator are placed thereon, and a positive electrode is placed so as to face the negative electrode, and the gasket and the sealing plate are caulked to form a secondary battery.

The non-aqueous solvent that can be used for the electrolytic solution includes
Propylene carbonate, ethylene carbonate, die
Chill carbonate, dimethyl carbonate, ethyl meth
Rucarbonate, 1,2-dimethoxyethane, γ-buty
Lolactone, tetrahydrofuran, 2-methyltetrahi
With drofuran, sulfolane, 1,3-dioxolane, etc.
Machine solvent used alone or as a mixture of two or more
Can be 0.5 to 2.0M in these solvents
LiClO_Four, LiPF₆, LiBF _Four, LiCF_Three
SO_Three, LiAsF₆Dissolve the electrolyte such as
You.

In addition, alkali metal catalysts such as lithium ions
Using solid polymer electrolytes, which are conductors of thione
You can also The material of the positive electrode body is not particularly limited, but lithium
It absorbs alkali metal cations such as um ions during charging and discharging.
A metal chalcogen compound that can be stored and released is preferred.
Good. Such metal chalcogen compounds include vana
Oxide ofdium, sulfide of vanadium, acid of molybdenum
Compounds, molybdenum sulfides, manganese oxides, chromium
Oxides, titanium oxides, titanium sulfides and these
Complex oxides, complex sulfides, and the like. Preferably
Is Cr_ThreeO₈, V_TwoO_Five, V_FiveO₁₃, VO_Two, Cr_Two
O_Five, MnO_Two, TiO_Two, MoV_TwoO₈, TiS_TwoV
_TwoS_FiveMoS_Two, MoS_ThreeVS_Two, Cr_0.25V
_0.75S_Two, Cr_0.5V_0.5S_TwoAnd so on. Also, LiM
Y_Two(M is a transition metal such as Co and Ni, and Y is a transition metal such as O and S.
Rucogen compound), LiM_TwoY_Four(M is Mn, Y is
O), WO_ThreeOxides such as CuS, Fe_0.25V
_0.75S_Two, Na_0.1CrS_TwoSulfides such as NiPS_Three,
FePS_ThreeSuch as phosphorus, sulfur compounds, VSe_Two, NbSe
_ThreeAnd the like can also be used. these
Like the negative electrode material, mix with the binder and apply it on the current collector.
A positive electrode plate is used.

The separator that holds the electrolytic solution is generally a material having excellent liquid retaining properties, and is impregnated with the electrolytic solution using, for example, a non-woven fabric of polyolefin resin or a porous film. Among the evaluation contents, negative electrode charge and discharge capacity,
The cycle characteristics, the potential-capacity curve, and the like were measured as follows. The above-mentioned negative electrode material molded into a pellet using a binder was combined with a separator and an electrolytic solution into a half battery having a lithium metal counter electrode, assembled in a 2016 coin cell, and evaluated by a charge / discharge tester.

On the other hand, the resistivity was calculated by measuring the surface resistance of the above negative electrode material processed into a sheet using a binder by the four-point probe method. When the test was conducted under such conditions, the IR drop in the carbon negative electrode plate of the present invention was decreased, the potential showed a discharge voltage of +0.5 V or less with respect to Li / Li ⁺ , and the rate characteristics were Was excellent.

As described above, in the lithium ion secondary battery electrode of the present invention, by adding a conductive filler to the carbonaceous material, the IR drop in the carbon negative electrode is reduced and the potential is higher than that of Li / Li ⁺ . A flat portion came to appear near the potential. In addition, due to the electron transfer rate control in the high resistance carbon particles, lithium ions are doped even in the parts that were not used, and the charge and discharge capacity originally possessed by the carbonaceous material can be efficiently achieved even during rapid charge and discharge. You can now withdraw.

[0025]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

Example 1 An artificial graphite powder (KS-manufactured by TIMCAL) was placed in a stainless steel tank having an internal volume of 20 liters.
6; particle size 2 to 3 mm) obtained by decomposing naphtha ethylene heavy end tar (EHE; manufactured by Mitsubishi Chemical Corporation)
20, 50 in volume% by weight (Vol.%) With respect to 7.0 L
The respective amounts were adjusted to be 420 and 1700 g by weight, and mixed by a hand mixer for 20 minutes. The internal temperature of the obtained slurry-like mixture was kept at 300 ° C.,
Furthermore, the degree of pressure reduction is set to 87.99 × 10 ³ Pa (660 torr).
Into the heating mixer described in r), deaeration and devolatilization are performed,
Removal of the light fraction of ethylene heavy end tar,
The product, a semi-solid solution, was recovered. Thus, a mixture of the conductive filler and the heat-treated pitch was obtained.

The above pitch containing the conductive filler KS-6 was placed in a batch type heating furnace under an inert atmosphere.
The temperature was kept at 00 ° C. and heat treatment was performed for 1 hour. This was crushed and adjusted to a particle size of 7 to 20 μm by a vibrating screen before being used as a sample. When the sample was subjected to elemental analysis and H / C was measured, it was 0.1 to 0.2. The BET specific surface area was 20 to 30 m ² / g. To 5 g of this electrode material sample, 10% by weight of a polyvinylidene fluoride (PVdF) dimethylacetamide solution in terms of solid content was added and stirred to obtain a slurry. This slurry was applied on a copper foil and pre-dried at 80 ° C. After further pressure bonding, it was punched into a disk having a diameter of 20 mm, and dried under reduced pressure at 110 ° C. to form an electrode.

The same slurry was coated on a polyethylene terephthalate thin film and predried at 80 ° C. 5
After removing a portion other than a square of 5 cm × 5 cm with a cutter, vacuum drying was performed at 110 ° C. The results of measuring the resistivity of this product are shown in Table 1. The obtained electrode was sandwiched with a polypropylene separator impregnated with an electrolytic solution to prepare a coin-shaped cell facing a lithium metal electrode, and a charge / discharge test was conducted. As the electrolytic solution, a solution in which lithium perchlorate was dissolved at a ratio of 1.0 mol / L in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was used.

The standard charge / discharge test was conducted at a current density of 0.16 mA.
/ Cm ² Dope until the potential difference between the electrodes becomes 0 V,
A current density of 0.33 mA / cm ² and a potential difference between the electrodes of 1.5 V
It was dedoped until it became. The capacity value was evaluated by conducting a charge / discharge test on each of three coin type cells and calculating the initial dedoping capacity. Table 2 shows the evaluation results.

(Comparative Example 1) The same operation as in Example was carried out except that the filler was not added to the heavy oil as the raw material. The resistivity is shown in Table 1 and the evaluation result is shown in Table 2.

(Example 2) The internal temperature was maintained at 100 ° C,
Ketjen black powder (KB; particle size 1 μm or less, manufactured by Mitsubishi Chemical Co., Ltd.) was added to ethylene heavy end tar (EHE; Mitsubishi Chemical Co., Ltd.) in a Z-blade mixer having an internal volume of 10 liters.
Manufactured by)) 1.4 L by volume% by weight of 20, 30, 50
(Weight, 60, 100 and 150 g respectively) were adjusted and mixed. The pitch containing carbon black as the conductive filler was degassed and volatilized by treating it at 700 ° C. for 1 hour in a batch heating furnace in an inert atmosphere.
The obtained solid content was crushed to 5 to 20 μm and used as a sample. When the sample was subjected to elemental analysis and H / C was measured, it was 0.2 to 0.3. The BET specific surface area was 10 to 70 m ² / g.

To 5 g of this sample was added a polyvinylidene fluoride (PVdF) dimethylacetamide solution in an amount of 10% by weight in terms of solid content, and the mixture was stirred to form a slurry. This was applied on a copper foil, preliminarily dried at 80 ° C., punched into a disk shape with a diameter of 20 mm, and dried under reduced pressure by heating at 110 ° C. to obtain an electrode pellet. Moreover, the same slurry was applied onto a polyethylene terephthalate thin film,
Pre-drying was performed at ° C. This was molded into a size of 20 cm × 10 cm, and heated and vacuum dried at 110 ° C. Table 1 shows the resistivity of these materials.

A coin-type cell having a structure in which a polyethylene separator impregnated with an electrolyte was sandwiched between the electrode pellet and a lithium metal electrode was prepared and a charge / discharge test was conducted. The electrolytic solution used was a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 50/50 and lithium perchlorate was dissolved in 1.0 mol / L. In the charge / discharge test, doping was performed at a current density of 0.16 mA / cm ² until the potential difference between the electrodes became 0 V, and the current density was 0.
Dedoping was performed at 33 mA / cm ² until the inter-electrode potential difference became 1.5 V.

In the rapid charge / discharge test, the current density was 0.
Doping was performed at 4 mA / cm ² until the potential difference between the electrodes became 0 V, and when the current density was 2.8 mA / cm ² , the potential difference between the electrodes was 1.
Dedoping was performed until the voltage became 5V. The capacity value was evaluated by performing a charge / discharge test on each of three coin cells and calculating the initial dedoping capacity (reference dedoping capacity and rapid dedoping capacity) of each of them. Table 2 shows the evaluation results.

(Example 3) The internal temperature was kept at 100 ° C,
Graphite powder (TIM
CAL SFG-6; particle size 4-5 mm) with ethylene heavy end tar (EHE; manufactured by Mitsubishi Chemical Corporation) 1.
It was adjusted so as to be 20 (85 g by weight) in volume% with respect to 4 L, and mixed. SFG- which is a conductive filler
The pitch containing 6 was treated in a batch heating furnace in an inert atmosphere at 700 ° C. for 1 hour for deaeration and volatilization. The obtained solid content was crushed to 7 to 20 μm and used as a sample. The sample was subjected to elemental analysis and H / C was measured to be 0.153. The BET specific surface area is 2
It was 6 m ² / g.

To 5 g of this sample was added a polyvinylidene fluoride (PVdF) dimethylacetamide solution in an amount of 10% by weight in terms of solid content, and the mixture was stirred and processed into a slurry form. This was applied on a copper foil, preliminarily dried at 80 ° C., punched into a disk shape with a diameter of 20 mm, and dried under reduced pressure by heating at 110 ° C. to obtain an electrode pellet. Moreover, the same slurry was applied onto a polyethylene terephthalate thin film,
Pre-drying was performed at ° C. This was molded into a size of 20 cm × 10 cm, and heated and vacuum dried at 110 ° C. Table 1 shows the resistivity of these materials.

A coin-type cell having a structure in which a polyethylene separator impregnated with an electrolyte was sandwiched between the electrode pellet and a lithium metal electrode was prepared and a charge / discharge test was conducted. The electrolytic solution used was a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 50/50 and lithium perchlorate was dissolved in 1.0 mol / L. In the charge / discharge test, doping was performed at a current density of 0.16 mA / cm ² until the potential difference between the electrodes became 0 V, and the current density was 0.
Dedoping was performed at 33 mA / cm ² until the inter-electrode potential difference became 1.5 V. The capacity value was evaluated by performing a charge / discharge test on each of three coin cells and calculating the initial de-doping capacity thereof. Table 2 shows the evaluation results.

(Example 4) The internal temperature was kept at 100 ° C,
Carbon fiber powder (CF; 15 μm crushed product, Petka Co., Ltd.) ethylene heavy end tar (EHE; Mitsubishi Chemical Co., Ltd.) in a Z-blade mixer with an internal volume of 10 liters.
20% by volume% (60 by weight)
g), and mixed. The pitch containing carbon black as the conductive filler was degassed and volatilized by treating it at 700 ° C. for 1 hour in a batch heating furnace in an inert atmosphere. The obtained solid content was pulverized to 17 to 20 μm and used as a sample. The sample is subjected to elemental analysis and H / C
Was 0.158. Also, BET
The specific surface area was 27 m ² / g.

To 5 g of this sample was added a polyvinylidene fluoride (PVdF) dimethylacetamide solution in an amount of 10% by weight in terms of solid content, and the mixture was stirred to form a slurry. This was applied on a copper foil, preliminarily dried at 80 ° C., punched into a disk shape with a diameter of 20 mm, and dried under reduced pressure by heating at 110 ° C. to obtain an electrode pellet. Moreover, the same slurry was applied onto a polyethylene terephthalate thin film,
Pre-drying was performed at ° C. This was molded into a size of 20 cm × 10 cm, and heated and vacuum dried at 110 ° C. Table 1 shows the resistivity of these materials.

A coin-type cell having a structure in which a polyethylene separator impregnated with an electrolyte was sandwiched between a lithium metal electrode and the electrode pellet was prepared and a charge / discharge test was conducted. The electrolytic solution used was a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 50/50 and lithium perchlorate was dissolved in 1.0 mol / L.

The charge / discharge test was conducted at a current density of 0.16 mA / cm.
² performs doped to interelectrode potential difference is 0V, the was dedoped at a current density of 0.33 mA / cm ² until the interelectrode potential difference 1.5V. The capacity value was evaluated by performing a charge / discharge test on each of three coin cells and calculating the initial de-doping capacity thereof. Table 2 shows the evaluation results.

[0042]

[Table 1] Table 1 Resistivity (Example 1) Ω · cm EHE80 volume% / KS-6 20 volume% 3.63 × 10 ¹ EHE50 volume% / KS-6 50 volume% 1.04 × 10 ¹ (Example 2) Ω Cm EHE80 volume% / KB20 volume% 3.65 × 10 ¹ EHE70 volume% / KB30 volume% 1.76 × 10 ¹ EHE50 volume% / KB50 volume% 4.86 × 10 ⁰ (Example 3) Ω · cm EHE80 volume% / SFG-620 Volume% 8.94 × 10 ¹ (Example 4) Ω · cm EHE 80 volume% / CF 20 volume% 1.6 × 10 ² (Comparative example 1) Ω ・ cm 5.70 × 10 ³

[0043]

[Table 2] Table 2 Reference dedoping capacity Rapid dedoping capacity 0.33 mA / cm ² 2.8 mA / cm ² (Example 1) mAh / g EHE80 volume% / KS-6 20 volume% 557 EHE50 volume% / KS-6 50 volume% 609 (Example 2) mAh / g mAh / g EHE80 volume% / KB20 volume% 633 339 EHE70 volume% / KB30 volume% 634 331 EHE50 volume% / KB50 volume% 641 310 (Example 3) mAh / g EHE 80 volume% / SFG-620 volume% 557 (Example 4) mAh / g EHE 80 volume% / CF 20 volume% 516 (Comparative example 1) mAh / g EHE 485 307

[0044]

The lithium ion secondary battery using the carbonaceous material containing the conductive filler of the present invention as the negative electrode is
The IR drop in the carbon negative electrode plate is reduced, and the potential is Li
Since a discharge potential of 0.5 V or less is applied to / Li +, the lithium ion secondary battery has excellent rate characteristics.

Claims (7)

[Claims] 1. A lithium ion secondary battery comprising a negative electrode which is an electrode material comprising a carbonaceous material capable of inserting and extracting lithium ions and containing a conductive filler. 2. A carbonaceous material capable of occluding and releasing lithium ions is obtained by firing an organic material at 400 ° C. or higher and 950 ° C. or lower, and has a volume resistivity of 10 ¹ Ω · cm or more and 10 or more.
⁷ Ω · cm or less, specific surface area 1 m ² / g or more, 100 m
² / g or less, H / C (hydrogen / carbon atom abundance ratio) is 0.0
The lithium ion secondary battery according to claim 1, which is amorphous carbon defined by 5 or more and 0.5 or less. 3. The electrode material contains 85 to 50% by volume (Vo) of a carbonaceous material capable of absorbing and desorbing lithium ions.
l. %), And the conductive filler is 15 to 50 Vol. %
The lithium ion secondary battery according to claim 1 or 2, wherein 4. The volume resistivity of the conductive filler is 10 ¹ Ω.
-Lithium ion secondary battery according to any one of claims 1 to 3, which is less than cm. 5. An average particle diameter or an average major axis of the conductive filler is in the range of 0.05 to 90% of the average particle diameter of the carbonaceous material capable of storing and releasing metal ions after firing. The lithium ion secondary battery according to claim 1. 6. The conductive filler is at least one selected from carbon black, graphite powder, carbon fiber and metal powder.
The lithium ion secondary battery according to claim 1, wherein the lithium ion secondary battery is a seed. 7. The lithium ion secondary battery according to claim 6, wherein the metal powder is at least one selected from nickel, copper and stainless steel.