JP4950166B2 - Negative electrode material, negative electrode using the same, and lithium ion battery and lithium polymer battery using the negative electrode - Google Patents

Description

  The present invention relates to a negative electrode material that can improve high rate charge / discharge characteristics and increase the energy density of a battery, a negative electrode using the negative electrode material, and a lithium ion battery and a lithium polymer battery using the negative electrode.

In recent years, along with the development of portable electronic devices such as mobile phones and laptop computers, and the practical application of electric vehicles, secondary batteries with small size and light weight and high capacity have been required. Currently, lithium ion batteries using lithium-containing composite oxides such as LiCoO ₂ as a positive electrode material and carbon-based materials as a negative electrode active material are commercialized as high-capacity secondary batteries that meet this requirement. In the secondary battery using carbon as the negative electrode active material, various types of carbon have been studied so far.
For these, carbon-based materials such as coal, coke, polyacrylonitrile (PAN) -based carbon fibers, pitch-based carbon fibers, carbonized organic materials (low-temperature heat treatment), etc. have been studied. Graphite-based materials include natural graphite. Artificial graphite, synthetic graphite, mesocarbon microbeads, graphitized (high-temperature heat-treated) products of organic substances, graphite fibers, and the like have been studied.

A negative electrode material using a carbon-based material is excellent in initial charge capacity, but initial charge / discharge efficiency is low and cycle characteristics are inferior. On the other hand, a negative electrode material using a graphite-based material is a carbon-based material. Compared with, the cycle characteristics are excellent, but the initial charge capacity is low and the charge / discharge rate is low.
In order to compensate for these problems, the use of a mixture of carbon-based materials and graphite-based materials has also been studied. However, a negative electrode material obtained by mixing a carbon-based material and a graphite-based material has many problems such as a small charge / discharge capacity, a low initial charge / discharge efficiency, a slow charge / discharge rate, and a short cycle life.

As a technique for solving the above problems, pitch carbonaceous fiber milled having an average particle diameter of less than 10 μm obtained at a heat treatment temperature of 550 ° C. or more and 1300 ° C. or less is contained in an amount of 60 wt% or more and 98 wt% or less and 2400 ° C. or more. There is disclosed a negative electrode material for a lithium ion secondary battery comprising 2 wt% or more and 40 wt% or less of pitch-based graphite fiber milled having an average particle size of 10 μm or more and 30 μm or less obtained at a heat treatment temperature of (for example, (See Patent Document 1).
In this negative electrode material, the pitch-based carbon fiber mill is subjected to heat treatment to reduce the radical concentration of the defective portion existing in the surface layer portion, and by removing oxygen-containing functional groups, the irreversible capacity of Li is reduced. This significantly improves the charge / discharge rate and cycle characteristics. Furthermore, a negative electrode material was prepared by mixing the pitch-based carbon fiber milled and pitch-based graphite fiber milled thus surface-modified in a predetermined ratio, and a negative electrode was manufactured using this negative electrode material. In this case, the negative electrode has a large discharge capacity, suppresses decomposition of the electrolytic solution, and has excellent cycle characteristics.
JP-A-9-310591

However, it is difficult for the pitch-based carbonaceous fiber milled contained in the negative electrode material disclosed in Patent Document 1 to have an average particle size of 1 μm or less, and the pitch-based carbonaceous fiber milled has an average particle size of 1 μm. There is a problem that a sufficient charge / discharge capacity cannot be obtained if the size exceeds this range.
An object of the present invention is to provide a negative electrode material and a negative electrode using the same, in which insertion and desorption reactions of lithium ions accompanying charge / discharge proceed smoothly and high-rate charge / discharge characteristics are improved.
Another object of the present invention is to provide a lithium ion battery and a lithium polymer battery that can increase the energy density of the battery.

As shown in FIGS. 1 and 2, the invention according to claim 1 is a laminate of a plurality of particulate first carbon materials 11 having an average particle diameter of 5 μm to 40 μm and a planar graphite net 12 having an average diameter of 10 nm to 500 nm. In addition to the carbon nanofibers 13 as shown in FIG. 5, a carbon fine powder having a graphite structure as a main component is a carbon nanofiber 13 whose graphite net is substantially perpendicular to the longitudinal axis of the fiber . The carbon nanofibers 13 included in the second carbon material 14 have a length of 1000 nm or more and an aspect ratio of 10 or more. 11 is composed of 98% to 70% by weight and the second carbon material 14 is composed of 2% to 30% by weight . The second carbon material 14 fills the voids formed by the first carbon material 11. It is filled. The second carbon material 14 is carbon nanofibers 13 80 wt% to 99.5 wt%, the negative electrode material is particulate agglomerates 16, wherein the proportion der Rukoto of 0.5 wt% to 20 wt% is there.
In the invention according to claim 1, when an electrode of a battery is produced using the negative electrode material of the present invention including the first carbon material 11 having a large average particle size and the second carbon material 14 having a nano size, Since the second carbon material 14 is filled in the void formed by the first carbon material 11 having a shape, the packing density of the carbon material in the electrode is effectively improved. Further, since the carbon nanofiber 13 having a length of 1000 nm or more and an aspect ratio of 10 or more, which is the main component of the second carbon material 14, exposes many edge surfaces of the graphite network 12, the carbon nanofiber 13 is used as the main component. By using the negative electrode material of the present invention that includes the second carbon material 14 and the first carbon material 11 that is a carbon material that has been conventionally used, compared to the case where only the conventional carbon material is used as the negative electrode material, As a result, lithium ion insertion and desorption reactions during charging and discharging proceed smoothly, and high rate charge and discharge characteristics are improved. Furthermore, since the second carbon material 14 is a material having an average diameter smaller than that of conventionally used carbon materials, when a battery electrode is manufactured, charging can be performed at a high density, and the energy density of the battery. It leads to improvement.

Further, by including the particulate aggregate 16 in the second carbon material 14, the contact between the carbon nanofibers 13 which are the main components is improved, and the high rate charge / discharge characteristics are further improved.

The invention according to claim 2 is the invention according to claim 1, the graphite-net plane is measured in the X-ray diffraction of the second carbon material 14 containing mosquitoes over carbon nanofibers 13 and particulate aggregate 16 respectively stacking spacing d ₀₀₂ is a negative electrode material is 0.3354Nm～0.339Nm.
The invention according to claim 3 is the invention according to claim 1 or 2 , and as shown in FIG. 5, the second carbon material 14 is either a metal having an average particle diameter of 10 nm to 500 nm or a metal oxide 17. Or it is a negative electrode material which further contains both of 0.5 weight%-10 weight%.
In the invention according to claim 3 , since the second carbon material 14 further includes a metal or metal oxide 17 having an average particle diameter of 10 nm to 500 nm, the metal or metal oxide serves as a base point for electron conduction. Rate discharge is possible.

The invention according to claim 4, an invention according to claims 1 to 3 any one of the exposed portions of the second carbon material 14 containing mosquitoes over carbon nanofibers 13 and particulate aggregate 16 respectively at least 85 % Is the negative electrode material that is the end of the graphite net.
The invention according to claim 5 is the invention according to claim 3, wherein either one or both of a metal and a metal oxide are on the long axis of the carbon nanofiber.

The invention according to claim 6 is the invention according to claim 3 or 5 , wherein the metal is at least one element selected from the group consisting of Fe, Co, Ni, Mg, Al, Mn and Cu. It is a negative electrode material.

The invention according to claim 7 is the invention according to claim 1, wherein the particulate first carbon material 11 is coal, coke, PAN-based carbon fiber, pitch-based carbon fiber, organic carbonized product, natural graphite, The negative electrode material includes at least one selected from the group consisting of artificial graphite, synthetic graphite, mesocarbon microbeads, organic graphitized products, and graphite fibers.
The invention according to claim 8 is a negative electrode formed using the negative electrode material according to any one of claims 1 to 7 and a conductive additive.
In the negative electrode described in claim 8 , since the insertion and extraction of lithium ions proceed smoothly by the carbon nanofiber formed by laminating a plurality of graphite nets which are the main component of the second carbon material, Discharge characteristics are improved.

The invention according to claim 9 is a lithium ion battery formed using the negative electrode according to claim 8 .
The invention according to claim 10 is a lithium polymer battery formed using the negative electrode according to claim 8 .
In the lithium ion battery or the lithium polymer battery described in claim 9 or 10 , smooth insertion and extraction of lithium ions is achieved by carbon nanofibers formed by laminating a plurality of graphite nets, which are the main component of the second carbon material. Therefore, the high rate charge / discharge characteristics are improved. In addition, since the second carbon material uses carbon nanofibers that are smaller in size than conventionally used carbon materials, charging at a high density is possible, leading to an improvement in the energy density of the battery.

As described above, the negative electrode material according to the present invention is formed by laminating a plurality of particulate first carbon materials having an average particle diameter of 5 μm to 40 μm and a planar graphite network having an average diameter of 10 nm to 500 nm. A carbon nanofiber that is substantially perpendicular to the axis as a main component, and in addition to the carbon nanofiber, each further includes a second carbon material including a particulate aggregate in which the carbon nanofiber is aggregated in the form of particles , The carbon nanofiber contained in the second carbon material has a length of 1000 nm or more and an aspect ratio of 10 or more, the first carbon material is 98 wt% to 70 wt%, and the second carbon material is 2 wt% to 30 wt%. % , The second carbon material is filled in voids formed by the first carbon material, and the second carbon material is composed of 80% to 99.5% carbon nanofibers. The amount%, Ru ratio der particulate agglomerates 0.5 wt% to 20 wt%.
When an electrode of a battery is produced using the negative electrode material of the present invention including the first carbon material having a large average particle size and the nano-sized second carbon material, the second carbon material is in the void formed by the first carbon material. Since it is filled, the packing density of the carbon material in the electrode is effectively improved. In addition, carbon nanofibers having a length of 1000 nm or more, which is the main component of the second carbon material, and an aspect ratio of 10 or more expose many edges of the graphite network. By using the negative electrode material of the present invention each including the first carbon material, which is a carbon material that has been conventionally used, and lithium associated with charge and discharge compared to the case where only the conventional carbon material is used as the negative electrode material Ion insertion and desorption reactions proceed smoothly, improving high rate charge / discharge characteristics. Furthermore, since the second carbon material is a material having an average diameter smaller than that of the conventionally used carbon material, when the battery electrode is produced, it becomes possible to charge at a high density and to improve the energy density of the battery. It leads to.
In addition, the negative electrode material of the present invention has good contact between carbon nanofibers, which are the main components, because the second carbon material contains particulate aggregates in which the carbon nanofibers are aggregated in the form of particles in addition to the carbon nanofibers. Thus, the high rate charge / discharge characteristics are further improved.

Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the negative electrode of the lithium ion battery or the lithium polymer battery includes a particulate first carbon material 11 having an average particle diameter of 5 μm to 40 μm and a planar graphite network 12 having an average diameter of 10 nm to 500 nm. A plurality of laminated negative electrodes are used, each including a second carbon material 14 mainly composed of carbon nanofibers 13 whose graphite net is substantially perpendicular to the longitudinal axis of the fiber. The carbon nanofibers 13 included in the second carbon material 14 are configured to have a length of 1000 nm or more and an aspect ratio of 10 or more. When a battery electrode is produced using the negative electrode material of the present invention including the first carbon material 11 having a large average particle size and the second carbon material 14 having a nano size, voids formed by the first carbon material 11 Since the second carbon material 14 is filled, the packing density of the carbon material in the electrode is effectively improved. Also, as shown in FIG. 4, one side of the end portion 12a having the graphite mesh 12 is joined to one side of the end portion of another graphite mesh, and one side of the other end portion is one side of the end portion of another graphite net. Carbon nanofibers 13 formed by bonding to each other and having a structure folded from each side may be used.

  In the negative electrode material of the present invention, the first carbon material 11 is composed of 98 wt% to 70 wt% and the second carbon material 14 is composed of 2 wt% to 30 wt%. The ratio of the first carbon material 11 to 95 wt% to 80 wt% and the second carbon material 14 to 5 wt% to 20 wt% is preferable. When a negative electrode is formed using a negative electrode material in which the proportion of the first carbon material 11 is less than 70% by weight, the packing density of the carbon material does not increase, and a negative electrode material in which the proportion of the first carbon material 11 exceeds 98% by weight is used. When the negative electrode is formed, the content ratio of the second carbon material is small, and the void formed by the first carbon material is not sufficiently filled.

  Since the second carbon material 14 mainly composed of the carbon nanofibers 13 of the present invention has a shape in which a plurality of graphite nets 12 are laminated and the graphite nets are substantially perpendicular to the longitudinal axis of the fiber. Many edge surfaces of the mesh 12 are exposed, and there are a number of layers formed by each graphite mesh in which lithium ions are inserted and desorbed. Therefore, a high rate discharge is possible because many lithium ions can be inserted and desorbed between the graphite network layers. Moreover, the insertion and detachment | desorption reaction of lithium ion accompanying charging / discharging advances smoothly by making the average diameter of the graphite network 12 into the range of 10 nm-500 nm. If the average diameter of the graphite net 12 is less than 10 nm, the space for inserting lithium ions is insufficient, and the effect of improving the energy density is difficult to obtain. If the thickness exceeds 500 nm, it is difficult to diffuse even if lithium ions are inserted between the layers formed by the graphite network, and the charge / discharge reaction does not proceed smoothly.

  As shown in FIG. 3A, a reaction occurs in which lithium ions are inserted between graphite network layers during charging. The inserted lithium ions diffuse between the graphite network layers (FIG. 3B). During discharge, lithium ions diffused between the graphite network layers cause a desorption reaction smoothly (FIG. 3 (c)). As described above, by using the carbon nanofiber of the present invention for the second carbon material, the lithium ion insertion and desorption reactions that accompany charge / discharge proceed smoothly, so that high rate charge / discharge characteristics are improved. In addition, carbon nanofibers are smaller in size than carbon materials that have been used in the past, so when battery electrodes are fabricated, charging at high density is possible, leading to improved battery energy density. .

  In addition to the carbon nanofibers 13, the second carbon material of the present invention further includes a particulate aggregate 16 made of fine carbon powder having a graphite structure. The content of the carbon nanofibers 13 in the second carbon material is 80 wt% to 99.5 wt%, and the content of the particulate aggregate 16 is a ratio of 0.5 wt% to 20 wt%. Preferably, the carbon nanofibers 13 are 90 wt% to 99 wt%, and the particulate aggregates 16 are 1 wt% to 10 wt%. The reason why the content of the carbon nanofibers 13 is limited to the range of 80% by weight to 99.5% by weight is that when the amount is less than 80% by weight, a sufficient electrode density cannot be obtained, and the energy density is hardly improved. This is because it is difficult to obtain sufficient high rate discharge characteristics when it exceeds 5% by weight.

When the second carbon material 14 containing mosquitoes over carbon nanofibers 13 and particulate aggregate 16 respectively were measured in X-ray diffraction, laminated spacing d ₀₀₂ of the resulting graphite-net plane in the range of 0.3354nm~0.339nm It is. Preferred multilayer spacing d ₀₀₂ is 0.3355Nm～0.3380Nm.

It is preferred that at least 85% of the exposed portion of the second carbon material 14 containing mosquitoes over carbon nanofibers 13 and particulate aggregate 16 respectively are the ends of the graphite-net. More preferably, it is 90% or more. Here, the end portion of the graphite net indicates a portion represented by reference numeral 12a in FIGS.

  By further including 0.5% by weight to 10% by weight of either or both of the metal and metal oxide 17 having an average particle diameter of 10 nm to 500 nm, the metal or metal oxide 17 having an average particle diameter of 10 nm to 500 nm can be obtained. Since it becomes a base point for electron conduction, a higher rate of discharge becomes possible. Either the metal or the metal oxide or both are configured to lie on the long axis of the carbon nanofiber. As the metal, at least one element selected from the group consisting of Fe, Co, Ni, Mg, Al, Mn, and Cu is selected and used in the form of a single metal, an alloy, or a metal oxide.

  The particulate first carbon material 11 is made of coal, coke, PAN-based carbon fiber, pitch-based carbon fiber, organic carbonized product, natural graphite, artificial graphite, synthetic graphite, mesocarbon microbeads, organic graphite. And at least one selected from the group consisting of chemicals and graphite fibers.

Next, the manufacturing method of the negative electrode material of this invention is demonstrated.
First, a catalyst necessary for producing the second carbon material of the present invention is synthesized. The average particle diameter of this catalyst is a size suitable for producing a second carbon material with fine powder in the range of 10 nm to 500 nm. Examples of the catalyst include Fe-based fine powder, specifically, Fe—Ni alloy, Fe—Mn alloy, Fe—Cu alloy, Co metal, Al ₂ O ₃ and MgO metal oxide. The catalyst is pretreated and activated before producing the second carbon material. The catalyst is activated by heating in a mixed gas atmosphere containing He and H ₂ .

FIG. 6 shows a heat treatment furnace 20 for producing the second carbon material of the present invention. The heat treatment furnace 20 includes an apparatus main body 21 made of a heat insulating material, and the inside of the apparatus main body 21 is horizontally partitioned by two partition plates 26 at a predetermined interval. A heating element 22 is installed on the top and bottom of the apparatus main body 21 partitioned by the partition plates 26, 26, respectively. Examples of the heating source of the heating element 22 used for heat treatment in the heat treatment furnace include an incandescent lamp, a halogen lamp, an arc lamp, and a graphite heater. A gas supply port 24 is provided on one side of the apparatus main body 21 so as to supply the source gas to the space partitioned by the partition plates 26 and 26. Examples of the source gas include a mixed gas containing CO and H ₂ . C ₂ H ₂ , C ₆ H ₆ or the like may be used instead of CO. The space 27 partitioned by the partition plates 26, 26 has a size that can accommodate a table 28 in which a fine powder catalyst is dispersed. The other side of the apparatus main body 21 is placed outside the system in the heat treatment furnace 20. A gas outlet 29 for discharging the supplied source gas is provided. The table 28 accommodated in the space 27 is placed on the take-out table 31, and is provided so as to be accommodated and unloaded in the heat treatment furnace.

  After the fine powder catalyst 32 is placed on the table 28, the table 28 is taken out, placed on the stand 31, transported to the heat treatment furnace 20, and stored in the space 27 of the apparatus main body 21. Thereafter, the source gas is supplied from the gas supply port 24 and heated by the heating elements 22 and 22. The supply amount of the source gas is set to 0.2 L / min to 10 L / min, and the heating temperature is set to 500 ° C. to 700 ° C. The mixture 33 is heated while supplying the raw material gas and kept for 1 hour to 10 hours, whereby the mixture 33 containing the carbon nanofibers and the particulate aggregates grows through the catalyst 32. Since the obtained mixture 33 containing the carbon nanofibers and the particulate aggregate contains a catalyst, the mixture 33 obtained by unloading the table 28 from the heat treatment furnace 20 is taken out, and the mixture 33 is mixed with nitric acid, The catalyst 32 contained in the mixture 33 is removed by dipping in an acidic solution such as hydrochloric acid, sulfuric acid, or hydrofluoric acid. The catalyst 32 may be included in the mixture as it is, and the catalyst may be a metal or a metal oxide.

Next, as the particulate first carbon material 11, coal, coke, PAN-based carbon fiber, pitch-based carbon fiber, carbonized product of organic matter, natural graphite, artificial graphite, synthetic graphite, mesocarbon microbeads, graphitization of organic matter A material having an average particle diameter of 5 μm to 40 μm including at least one selected from the group consisting of a product and a graphite fiber is prepared.
The first carbon material 11 and the obtained second carbon material 14 are mixed at a ratio of 98 wt% to 70 wt% for the first carbon material 11 and 2 wt% to 30 wt% for the second carbon material 14. Thus, a negative electrode material is prepared.

A negative electrode is prepared using the negative electrode material of the present invention thus obtained.
First, a predetermined negative electrode material (negative electrode active material), a conductive additive (carbon powder or metal powder that is difficult to be alloyed with lithium such as copper or titanium), and a binder such as polyvinylidene fluoride (PVdF) are predetermined. A negative electrode slurry is prepared by mixing at a ratio of Here, the binder is mixed in a state dissolved in a solvent such as acetone. Next, the negative electrode slurry is applied to the upper surface of the negative electrode current collector foil by a screen printing method, a doctor blade method, or the like and dried to prepare a negative electrode. In addition, after apply | coating a negative electrode slurry on a glass substrate and drying, it peels from a glass substrate and produces a negative electrode film, Furthermore, this negative electrode film is piled up on a negative electrode collector, and is press-molded by predetermined pressure, and negative electrode May be produced. In the negative electrode manufactured in this way, the insertion and release of lithium ions proceeds smoothly by the carbon nanofibers formed by laminating a plurality of graphite nets, so that the high rate charge / discharge characteristics are improved.

  The obtained negative electrode of the present invention, a non-aqueous electrolyte [for example, a mixed solvent composed of ethylene carbonate (EC) and diethylene carbonate (DEC) (mixing weight ratio 1: 1) and lithium perchlorate are dissolved at 1 mol / liter. A positive electrode formed by applying and drying a positive electrode slurry comprising a binder, a positive electrode material and a conductive additive on a positive electrode current collector by a doctor blade method. Thus, a lithium ion battery is obtained. Further, a negative electrode of the present invention, a polymer electrolyte layer made of polyethylene oxide, polyvinylidene fluoride, or the like, and a positive electrode slurry made of a binder, a positive electrode material, and a conductive auxiliary agent are applied onto the positive electrode current collector by a doctor blade method and dried. A lithium polymer battery is obtained by laminating the positive electrode formed in this way. In the lithium ion battery and the lithium polymer battery manufactured as described above, the insertion and release of lithium ions proceed smoothly by the carbon nanofibers formed by stacking a plurality of graphite nets, so that the high rate charge / discharge characteristics are improved. . In addition, since carbon nanofibers that are smaller in size than conventional carbon materials are used, charging at a high density is possible, leading to an improvement in the energy density of the battery.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
(1) Production of Second Carbon Material First, an Fe—Ni alloy having an average particle size of 0.1 μm was used as a catalyst, and this catalyst was activated by heating in a mixed gas atmosphere containing He and H ₂ . Next, the activated catalyst was placed on a table, and the table was accommodated in a heat treatment furnace. Next, the inside of the heat treatment furnace is heated to a temperature of 550 ° C. to 630 ° C., and this raw material gas is supplied into the heat treatment furnace at a flow rate of 10 L / min using a mixed gas containing CO and H ₂ and held for about 10 hours. Thus, a mixture containing each of carbon nanofibers and particulate aggregates was synthesized. The obtained mixture was immersed in a nitric acid solution to remove the catalyst contained in the mixture to obtain a second carbon material. When this second carbon material was measured by X-ray diffraction, laminated spacing d ₀₀₂ of the graphite-net plane of a mixture containing carbon nanofibers and the particulate aggregate, respectively was 0.3362Nm.

(2) Production of negative electrode (working electrode) First, mesocarbon microbeads having an average particle diameter of 14 μm were prepared as the first carbon material, and the first carbon material and the second carbon material were 95% by weight: 5% by weight. A negative electrode material was prepared by mixing at a ratio. A negative electrode slurry was prepared by mixing 18 g of this negative electrode material, 2 g of polyvinylidene fluoride (PVdF), and 18 g of n-methylpyrrolidone. Next, the negative electrode slurry having a thickness of 0.09 cm was prepared by coating the negative electrode slurry on a glass substrate, drying it, and then peeling it off. This negative electrode film was cut into squares each having a length × width of 1.2 cm × 1.2 cm to obtain two square negative electrode films. Next, these negative electrode films were arranged on both sides of a square metal net-like negative electrode current collector of 1 cm × 1 cm × 0.1 cm in length × width × thickness, respectively, to prepare a laminate. A copper foil formed in a mesh shape was used for the negative electrode current collector. Further, the laminate was pressure-bonded by applying a pressure of 0.5 to 3 MPa with a press machine heated to 110 to 130 ° C. This obtained the negative electrode (working electrode).

<Example 2>
A negative electrode (working electrode) was produced in the same manner as in Example 1 except that the negative electrode material was prepared by mixing the first carbon material and the second carbon material in a ratio of 90% by weight to 10% by weight.
<Example 3>
A negative electrode (working electrode) was produced in the same manner as in Example 1 except that the negative electrode material was prepared by mixing the first carbon material and the second carbon material in a ratio of 80% by weight to 20% by weight.
<Example 4>
A negative electrode (working electrode) was produced in the same manner as in Example 1 except that the negative electrode material was prepared by mixing the first carbon material and the second carbon material in a ratio of 70% by weight to 30% by weight.

<Example 5>
A negative electrode (working electrode) was produced in the same manner as in Example 1 except that mesocarbon microbeads having an average particle diameter of 23 μm were used as the first carbon material.
<Example 6>
A negative electrode (working electrode) was produced in the same manner as in Example 2 except that mesocarbon microbeads having an average particle diameter of 23 μm were used as the first carbon material.
<Example 7>
A negative electrode (working electrode) was produced in the same manner as in Example 3 except that mesocarbon microbeads having an average particle diameter of 23 μm were used as the first carbon material.
<Example 8>
A negative electrode (working electrode) was produced in the same manner as in Example 4 except that mesocarbon microbeads having an average particle diameter of 23 μm were used as the first carbon material.

<Comparative Example 1>
A negative electrode (working electrode) was produced in the same manner as in Example 1 except that a spherical graphite material having an average particle size of 10 μm was used as the negative electrode material.
<Comparative example 2>
A negative electrode (working electrode) was produced in the same manner as in Example 1 except that a spherical graphite material having an average particle size of 25 μm was used as the negative electrode material.

<Comparison test and evaluation>
As shown in FIG. 7, the negative electrode 41 (working electrode) produced in each of Examples 1 to 8 and Comparative Examples 1 and 2 was attached to a charge / discharge cycle test apparatus 51. In this device 51, an electrolytic solution 53 (lithium salt dissolved in an organic solvent) is stored in a container 52, the negative electrode 41 is immersed in the electrolytic solution 53 together with the positive electrode 42 and the reference electrode 43, and further the negative electrode 41 (working electrode). ), The positive electrode 42 (counter electrode) and the reference electrode 43 are electrically connected to a potentiostat 54 (potentiometer), respectively. A solution containing 1M LiPF ₆ as the lithium salt and ethylene carbonate and diethyl carbonate as the organic solvent was used. Using this apparatus, a charge / discharge cycle test was performed to measure the low rate and high rate discharge capacity of each negative electrode (working electrode). The low-rate discharge capacity was measured at 70 mA / g, and the high-rate discharge capacity was measured at 500 mA / g, and the measurement voltage range was 0 V to 2.0 V. The measurement results of the electrodes of Examples 1 to 8 are shown in Table 1, and the measurement results of the electrodes of Comparative Examples 1 and 2 are shown in Table 2, respectively.

As is clear from Tables 1 and 2, in Comparative Examples 1 and 2 in which spherical graphite material having a large average particle diameter that has been used conventionally is used as the negative electrode material, the reduction in the high rate discharge capacity was remarkable. . Further, Comparative Example 2 having a larger particle size showed a lower electrode density than Comparative Example 1. On the other hand, Examples 1 to 8 using the negative electrode material of the present invention showed high electrode density, and there was no significant difference between the low rate discharge capacity and the high rate discharge capacity, and electrodes were produced using this material. In this case, it was found that the high rate discharge characteristics can be improved.

The schematic diagram of the negative electrode material of this invention. The schematic diagram of the carbon nanofiber which is a main component of the 2nd carbon material of this invention. The schematic diagram which shows reaction in which lithium ion inserts and detaches | leaves between graphite network layers. The schematic diagram of the carbon nanofiber which has another structure corresponding to FIG. The schematic diagram which shows a carbon nanofiber and a particulate aggregate. The cross-sectional block diagram of the heat processing furnace which produces the negative electrode material of this invention. The apparatus used for the charging / discharging cycle test of the negative electrode active material for lithium secondary batteries of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 1st carbon material 12 Graphite network 13 Carbon nanofiber 14 2nd carbon material 16 Particulate aggregate

Claims (10)

A plurality of particulate first carbon materials (11) having an average particle diameter of 5 μm to 40 μm and a planar graphite network (12) having an average diameter of 10 nm to 500 nm are laminated, and the graphite network is substantially aligned with respect to the longitudinal axis of the fiber. Second carbon material comprising carbon nanofibers (13) that are vertically vertical as a main component, and in addition to the carbon nanofibers (13), further comprising particulate aggregates (16) made of carbon fine powder having a graphite structure (14)
The carbon nanofiber (13) contained in the second carbon material (14) has a length of 1000 nm or more and an aspect ratio of 10 or more,
The first carbon material (11) is composed of 98 wt% to 70 wt%, and the second carbon material (14) is composed of 2 wt% to 30 wt% ,
The second carbon material (14) is filled in a void formed by the first carbon material (11),
The second carbon material (14) of the carbon nanofibers (13) is 80 wt% to 99.5 wt%, the particulate agglomerate (16) Ru ratio der of 0.5 wt% to 20 wt% A negative electrode material characterized by the above. Mosquitoes over carbon nanofibers (13) and the graphite-net to be measured in X-ray diffraction of the second carbon material comprising particulate aggregates (16), respectively (14) (12) stacked spacing d ₀₀₂ of the plane 0.3354nm~ anode material according to claim 1 Symbol placement is 0.339 nm. The average particle metals or metal oxides of diameter 10 nm to 500 nm (17) either or No mounting according to claim 1 or 2 SL that both further comprises 0.5 wt% to 10 wt% of the second carbon material (14) Negative electrode material. Mosquitoes over carbon at least 85% of the exposed portions of the nanofibers (13) and a second carbon material comprising particulate aggregates (16), respectively (14) claims 1 to an end portion of the graphite-net 3 any one The negative electrode material described in 1. Anode material according to claim 3 Symbol mounting either or both, it is on the long axis of the carbon nanofibers in the metal or metal oxide. The negative electrode material according to claim 3 or 5 , wherein the metal is at least one element selected from the group consisting of Fe, Co, Ni, Mg, Al, Mn, and Cu. Particulate first carbon material (11) is coal, coke, polyacrylonitrile carbon fiber, pitch carbon fiber, organic carbonized product, natural graphite, artificial graphite, synthetic graphite, mesocarbon microbeads, organic graphitization The negative electrode material according to claim 1, comprising at least one selected from the group consisting of an article and graphite fibers. Negative electrode formed using the negative electrode material according to claims 1 to 7 any one, and a conductive additive. A lithium ion battery formed using the negative electrode according to claim 8 . A lithium polymer battery formed using the negative electrode according to claim 8 .