JP3509050B2 - Lithium secondary battery and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithium secondary battery, and more particularly to a lithium secondary battery having an improved negative electrode containing a carbonaceous material.

[0002]

2. Description of the Related Art In recent years, non-aqueous electrolyte batteries using lithium as a negative electrode active material have been attracting attention as high energy density batteries, and manganese dioxide (MnO ₂ ) has been used as a positive electrode active material.
Fluorocarbon [(CF ₂ ) _n ], thionyl chloride (SOCl
₂ ) The primary batteries using these are already widely used as calculators, clock power supplies, and memory backup batteries.

Further, in recent years, with the reduction in size and weight of various electronic devices such as VTRs and communication devices, the demand for high energy density secondary batteries as their power source has increased, and lithium secondary batteries using lithium as a negative electrode active material. Batteries are being actively researched.

Lithium secondary batteries use lithium for the negative electrode and use propylene carbonate (PC), 1,2-dimethoxyethane (DME), γ-butyrolactone (γ-) as an electrolyte.
BL), tetrahydrofuran (THF) or the like, a non-aqueous electrolyte solution or a lithium ion conductive solid electrolyte in which a lithium salt such as LiClO ₄ , LiBF ₄ , or LiAsF ₆ is dissolved in a non-aqueous solvent, and a positive electrode active material is mainly used. TiS ₂ ,
The use of compounds such as MoS ₂ , V ₂ O ₅ , V ₆ O ₁₃ , and MnO ₂ that undergo a topochemical reaction with lithium has been studied.

However, the lithium secondary battery described above has not yet been put into practical use. The main reason for this is that the charging / discharging efficiency is low and the number of times charging / discharging is possible (cycle life) is short. It is considered that this is largely due to the deterioration of lithium due to the reaction between the negative electrode lithium and the non-aqueous electrolyte. That is, lithium that has been dissolved in the non-aqueous electrolyte as lithium ions during discharge reacts with the solvent during precipitation during charging, and its surface is partially inactivated. Therefore, when charging and discharging are repeated, lithium deposits in a dendrite-like (dendritic) or small spherical shape, and further lithium is desorbed from the current collector.

Further, it has been studied to use a lithium alloy whose composition formula is represented by Li _X A (A is a metal such as Al) as a negative electrode. Although this negative electrode has a large amount of lithium ions stored and released per unit volume and has a high capacity, it expands and contracts when the lithium ions are stored and released, so the alloy structure is destroyed when the lithium ions are repeatedly stored and released. It Therefore, the lithium secondary battery including the negative electrode has a problem that the charge / discharge cycle life is short.

From the above, by using a carbonaceous material that absorbs and releases lithium, such as coke, a resin fired body, carbon fiber, and pyrolysis vapor phase carbon, as a negative electrode incorporated in a lithium secondary battery, It has been proposed to improve the reaction with the non-aqueous electrolyte and further the deterioration of the negative electrode characteristics due to the deposition of dendrites.

In the carbonaceous material-containing negative electrode, in the carbonaceous material having a structure (graphite structure) in which hexagonal mesh plane layers mainly composed of carbon atoms are stacked, lithium ions are present between the layers. It is considered to charge and discharge by going in and out. Therefore, it is necessary to use a carbonaceous material having a graphite structure developed to some extent for the negative electrode of the lithium secondary battery. However, if a carbonaceous material obtained by powdering giant crystals that have advanced graphitization is used as a negative electrode in a non-aqueous electrolyte, the non-aqueous electrolyte decomposes, resulting in low battery capacity and charge / discharge efficiency. In addition, there is a problem in that the cycle life is shortened because the capacity decreases more as the charge / discharge cycle progresses.

[0009] Further, it is under study to increase the capacity of the negative electrode containing the carbonaceous material. From this, J. Elec
trochem. Soc. , Vol. 142, No. 1
1, Nomber 1995, pages 3668-367.
Table II on page 7 discloses a coin-type battery provided with a cathode containing a fired epoxy novolac resin having voids with a diameter of 7.4 to 8.8 angstrom by a small-angle X-ray scattering method, and an anode made of lithium foil. Has been done.

Further, J. Electrochem. S
oc. , Vol. 142, No. 2, February
1995 pages 326 to 332 have an X-ray diffraction d ₀₀₂ of 3.47 Å and a Si atom of 1.
Equipped with a cathode containing 8% of thermally decomposed vapor phase carbon and an anode made of lithium foil, the weight specific capacity is 363 mAh.
/ G of coin type lithium secondary battery is disclosed.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium secondary battery having improved discharge capacity and cycle life by improving a negative electrode containing a carbonaceous material.

[0012]

According to the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material which absorbs and releases lithium ions, and a non-aqueous electrolyte, wherein The carbonaceous material has an amorphous carbon structure region and a graphite structure region, and a powder X-ray diffraction spectrum shows a peak corresponding to d ₀₀₂ of 0.340 nm or less (however, d ₀₀₂ indicates a plane spacing of the (002) plane). Present and true density 1.8g
/ Cm ³ or more, there is provided a lithium secondary battery.

Further, according to the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolyte, wherein the carbonaceous material of the negative electrode is: It has an amorphous carbon structure region and a graphite structure region, and has a peak corresponding to d ₀₀₂ of 0.34 nm or less in the powder X-ray diffraction (provided that d ₀₀₂ indicates the (002) plane spacing), And the true density is 2-2.2 g / cm
Provided is a lithium secondary battery having the number of ³ or more and having voids having a diameter of 0.1 to 20 nm by the small angle X-ray scattering method in the amorphous carbon structure region. further,
According to the present invention, there is provided a method of manufacturing the lithium secondary battery.
Thus, the carbonaceous material is natural graphite, petroleum pitch,
Material selected from the group consisting of waze pitch and coke
Material, isotropic pitch, polyacrylonitrile, full free
Alcohol, furan resin, phenolic resin, cell
Selected from the group consisting of loin, sugar and polyvinylidene chloride
80 of a mixture containing a non-graphitizable carbon precursor.
Method comprising a step of heat treatment in the range of 0 to 3000 ° C
Of a lithium secondary battery characterized by being manufactured by
A manufacturing method is provided.

Further, according to the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolyte, wherein the carbonaceous material of the negative electrode is: It has an amorphous carbon structure region and a graphite structure region and has a d ₀₀₂ of 0.340 nm or less in powder X-ray diffraction.
(However, d ₀₀₂ indicates the interplanar spacing of (002) planes), the true density is 1.8 g / cm ³ or more, and the amorphous carbon structure region has 0.370 nm or more. Provided is a lithium secondary battery having d ₀₀₂ .

Further, according to the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material which absorbs and releases lithium ions, and a non-aqueous electrolyte, wherein the carbonaceous material of the negative electrode is: It contains Si and has a powder X-ray diffraction of 0.337.
A peak corresponding to d _{002 of} less than nm (however, the d ₀₀₂ indicates the interplanar spacing of the (002) plane) and the true density
Is 2 g / cm ³ or more, and a lithium secondary battery is provided. Further, according to the present invention, the positive electrode, the fibrous carbonaceous material that absorbs and releases lithium ions and the lithium ions that are absorbed and released, and the ratio of the minor axis to the major axis (minor axis / major axis) is 1/10 or more. A negative electrode containing a carbonaceous material containing at least one selected from the group consisting of certain spherical carbonaceous material particles; and a non-aqueous electrolyte solution,
The fibrous carbonaceous material and the spherical carbonaceous material particles are M
each containing at least one element M selected from the group consisting of g, Al, Si, Ca, Sn and Pb,
Further, there is provided a lithium secondary battery characterized in that there is a peak corresponding to d _{002 of} less than 0.337 nm (however, said d ₀₀₂ indicates the plane spacing of (002) plane) in powder X-ray diffraction. It Further, according to the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolyte, wherein the carbonaceous material of the negative electrode is Si and Al. Or both elements of Ca, Mg, or both elements of Si and Mg, and d ₀₀₂ of 0.344 nm or less in powder X-ray diffraction (provided that d ₀₀₂
Is a (002) plane spacing), and a lithium secondary battery is provided.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a lithium secondary battery (for example, a cylindrical lithium secondary battery) according to the present invention will be described in detail with reference to FIG. For example, a bottomed cylindrical container 1 made of stainless steel has an insulator 2 arranged at the bottom. The electrode group 3 is housed in the container 1. The electrode group 3 has a structure in which a band-shaped material in which a positive electrode 4, a separator 5 and a negative electrode 6 are laminated in this order is spirally wound so that the separator 5 is located outside.

An electrolytic solution is contained in the container 1. The insulating paper 7 having a central opening is placed above the electrode group 3 in the container 1. The insulating sealing plate 8 is
The sealing plate 8 is arranged in the upper opening of the container 1 and the vicinity of the upper opening is caulked inward.
Is liquid-tightly fixed to the container 1. The positive electrode terminal 9 is
It is fitted in the center of the insulating sealing plate 8. Positive electrode lead
One end of the battery 10 is connected to the positive electrode 4 and the other end is connected to the positive electrode terminal 9
Respectively connected to. The negative electrode 6 is connected to the container 1, which is a negative electrode terminal, via a negative electrode lead (not shown).

Next, the positive electrode 4, the separator 5, the negative electrode 6 and the electrolytic solution will be described in detail. 1) Positive Electrode 4 The positive electrode 4 is produced by suspending a conductive agent and a binder in an appropriate solvent in a positive electrode active material, applying the suspension to a current collector, and drying the suspension to form a thin plate.

As the positive electrode active material, various oxides,
For example, manganese dioxide, lithium manganese composite oxide,
Examples thereof include lithium-containing nickel oxide, lithium-containing cobalt compound, lithium-containing nickel-cobalt oxide, lithium-containing iron oxide, lithium-containing vanadium oxide, and chalcogen compounds such as titanium disulfide and molybdenum disulfide. Above all, when lithium cobalt oxide {Li _x CoO ₂ (0.8 ≦ x ≦ 1)}, lithium nickel oxide (LiNiO ₂ ) or lithium manganese oxide (LiMn ₂ O ₄ or LiMnO ₂ ) is used, a high voltage is obtained. Is preferred, which is preferable.

Examples of the conductive agent include acetylene black, carbon black, graphite and the like. Examples of the binder include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVD).
F), ethylene-propylene-diene copolymer (EPD
M), styrene-butadiene rubber (SBR) and the like can be used.

The mixing ratio of the positive electrode active material, the conductive agent and the binder is 80 to 95% by weight of the positive electrode active material and the conductive agent 3 to 2.
It is preferable that the content is 0% by weight and the binder is 2 to 7% by weight.

As the current collector, for example, aluminum foil, stainless foil, nickel foil or the like can be used. 2) Separator 5 As the separator 5, for example, a synthetic resin non-woven fabric,
A polyethylene porous film, a polypropylene porous film, or the like can be used.

3) Negative Electrode 6 The negative electrode 6 contains a carbonaceous material that absorbs and releases lithium ions. The carbonaceous material has a graphite structure region and an amorphous carbon structure region and has a multiphase structure. Further, the carbonaceous material has a peak corresponding to d ₀₀₂ of 0.340 nm or less in powder X-ray diffraction, and has a true density of 1.8 g / cm ^3.
That is all. Note that d ₀₀₂ is (002) of graphite crystallite
The spacing between the surfaces is shown.

The interplanar spacing d of the (002) plane of the carbonaceous material
₀₀₂ can be obtained from the peak position and the half width of the diffraction pattern obtained by powder X-ray diffraction. As the calculation method, the half-width half-point method specified in the Gakshin method is used. In the powder X-ray diffraction measurement, CuKα is used as an X-ray source,
High-purity silicon is used as a standard substance. The half-width half-point method is described in "Tanso (carbon)", 1963, p25.

FIG. 2 shows a schematic view of an example of the fine structure of the carbonaceous material. As shown in FIG. 2, the carbonaceous material has a multiphase structure and has a graphite structure region (graphite structure portion). This graphite structure region is mainly formed of a graphite crystallite C having a structure in which a plurality of hexagonal net surface layers 20 are arranged with a certain regularity. The carbonaceous material had a .0 in powder X-ray diffraction.
It has a peak corresponding to d ₀₀₂ of 340 nm or less. It is considered that such a peak is due to the graphite structure region. On the other hand, the carbonaceous material also has an amorphous carbon structure region (amorphous carbon structure portion). In the amorphous carbon structure region, there is no regularity in the arrangement of the hexagonal network plane layer 20 of graphite crystallites, and there are voids (defects) such as region D, for example. In such an amorphous carbon structure region, the structure is such that the void has a diameter of 0.1 to 20 nm according to the small-angle X-ray scattering method, or the interplanar spacing d ₀₀₂ of the (002) plane is 0.3.
70 nm or more is present, or the diameter of the voids is 0.1 to 20 n according to the small angle X-ray scattering method.
m and the surface spacing d ₀₀₂ of the (002) plane is 0.370.
It is preferable to have a structure in which a layer having a thickness of nm or more exists. This 0.
Most of the interplanar spacings of 370 nm or more are caused by the voids (however, the carbonaceous material has a d of 0.370 nm or more).
_When the abundance ratio of ₀₀₂ is below the detection limit of powder X-ray diffraction (about 10% by weight), it is 0.370 nm by powder X-ray diffraction
The peak corresponding to d ₀₀₂ cannot be detected).

The carbonaceous material has a powder X-ray diffraction pattern of 0.34.
It has a peak corresponding to d ₀₀₂ of 0 nm or less. It is difficult to improve the discharge capacity of a lithium secondary battery with a carbonaceous material that does not have such a peak. The carbonaceous material has d ₀₀₂ of 0.340 nm or less in powder X-ray diffraction.
May have only a peak corresponding to
A peak corresponding to d ₀₀₂ exceeding 0 nm may be present. However, 0.37 by powder X-ray diffraction
A carbonaceous material in which a peak corresponding to d ₀₀₂ of 0 nm or more is detected may have a true density of less than 1.8 g / cm ³ , and the volume specific capacity (mAh / cc) of the negative electrode may decrease. . A more preferable carbonaceous material has a peak corresponding to d ₀₀₂ of 0.338 nm or less in powder X-ray diffraction. A more preferable carbonaceous material is 0.
3354 to 0.340 nm (more preferably 0.33
It has a peak corresponding to d ₀₀₂ of 54 to 0.338 nm).

The true density of the carbonaceous material is 1.8 g / cm.
Set to ³ or more. The true density of the carbonaceous material is 1.8 g / cm
^{When it is} less than ³ , the graphite structure region in the carbonaceous material is insufficient and the graphitization degree of the graphite structure region is reduced, so that the volume specific capacity of the negative electrode is reduced. A true density of a carbonaceous material having a fine structure consisting only of a graphite structure region is 2.25 g / cm ³ , and a carbonaceous material having a fine structure in which a graphite structure region and an amorphous carbon structure region coexist at an appropriate ratio. Therefore, the upper limit of the true density of the carbonaceous material is preferably 2.2 g / cm ³ . A more preferable true density is 2.0 to 2.2 g /
It is in the range of cm ³ .

The measurement of the diameter of the void by the small angle X-ray scattering method is carried out by the method described below. That is, using a powder XX-ray apparatus having a trade name of D5000 manufactured by Siemens Co., and using Cu · Kα as a tube,
The measurement was performed in a transmission type arrangement. The measurement conditions are as follows. The sample holder is 13 mm in length and width, 9 mm in height and 1.5 m in thickness.
m chamber was used. The sample holder was arranged in the device so as to be orthogonal to the primary light beam. Polymer film with a thickness of 25 μm (K
(Apton foil) was used. The amount of carbonaceous material contained in the sample holder was set in the range of 150 mg to 200 mg. The incident angle and the anti-scattering angle were each set to 0.1 °. The width of the light-receiving slit was 0.1 mm.

The scattering angle was increased from 0.4 ° to 10 ° in steps of 0.05 °, and the small angle scattering intensity at each scattering angle was measured. Let I (q) be the average value of the obtained scattering intensities,
The radius of gyration R _{g of the} void was obtained from the formula (1) shown in the following mathematical formula 1.

[0030]

[Equation 1]

Here, q is a wave vector, N is the number of voids in the carbonaceous material, and V is the total volume of the voids. The obtained radius gyration R _g is substituted into the following formula (2) to obtain the diameter R _s of the voids of the carbonaceous material by the small angle X-ray scattering method.

R _g = (3/5) ^1/2 × R _s (2) The diameter of the voids (defects) in the amorphous carbon structure region of the carbonaceous material measured by the small-angle X-ray scattering method is 0.1 to 20 nm. It is preferably within the range. If the diameter of the voids deviates from this range, the amount of lithium ions stored in the amorphous carbon structure region may decrease, and it may not be possible to increase the capacity of the lithium secondary battery. More preferable diameter is 0.5 to
It is in the range of 5 nm. More preferable diameter is 0.5 to
It is in the range of 2 nm.

The carbonaceous material can be present in the negative electrode in the form of fibrous particles, spherical particles, or a mixture of fibrous particles and spherical particles. The fibrous carbonaceous material particles include, in addition to carbon fibers, particles obtained by crushing carbon fibers.

(1) Fibrous carbonaceous material particles The average fiber length of the fibrous carbonaceous material particles is 10 to 10.
It is preferably in the range of 0 μm.

The average fiber diameter of the fibrous carbonaceous material particles is
It is preferably in the range of 1 to 20 μm. The specific surface area of the fibrous carbonaceous material particles is 0.1 to ⁵ m ² / g.
Is preferred.

The fibrous carbonaceous material particles have an average fiber length of 10 to 100 μm and an average fiber diameter of 1 to 2.
When it is in the range of 0 μm, the aspect ratio (fiber length / fiber diameter) is preferably in the range of 2 to 10. When the aspect ratio of the fibrous carbonaceous material particles is less than 2,
The ratio of the cross-section of the fibrous carbonaceous material particles exposed on the surface of the negative electrode increases. As a result, in the Li ion occlusion / desorption reaction, the ratio of the occlusion / desorption reaction from the cross section of the fibrous carbonaceous material particles becomes high, so that the movement of Li ions into the fibrous carbonaceous material particles is slow. Therefore, the large current discharge performance may be deteriorated. In addition, the electrolytic solution may be decomposed and the charge / discharge efficiency may be reduced. Furthermore, the packing density of the fibrous carbonaceous material particles in the negative electrode is, for example, 1.
It may be difficult to raise it to ³ g / cm ³ or more. On the other hand, when the aspect ratio of the fibrous carbonaceous material particles exceeds 10, the fibrous carbonaceous material particles easily penetrate the separator, which may cause a short circuit between the positive electrode and the negative electrode.

Among the above fibrous carbonaceous material particles, the fibrous carbonaceous particles obtained by crushing carbon fibers have an average particle diameter of 1 to 100 μm, more preferably 2
It is desirable to be in the range of -40 μm.

The orientation of the graphite crystallites in the graphite structure region of the fibrous carbonaceous material particles is preferably radial. Here, the orientation of the graphite crystallites being radial means that the hexagonal network plane layers of the graphite crystallites present in the fibrous carbonaceous material particles face the outer peripheral surface of the fibrous carbonaceous material particles. The radial orientation also includes orientations belonging to lamella type and Brooks stella type. Of the fibrous carbonaceous material particles 21 having a radial orientation, FIG. 3 shows the fibrous carbonaceous material particles 21.
An example in which the hexagonal mesh plane layers of all the graphite crystallites 22 included in 1) face the outer peripheral surface of the fibrous carbonaceous material particles 21 is shown. The fibrous carbonaceous material particles 21 have voids 23 in the amorphous carbon structure region. Among the fibrous carbonaceous material particles in which the orientation of the graphite crystallites belongs to the radial type, those having an appropriate disorder in the orientation are preferable. The fibrous carbonaceous material particles having an appropriate disorder in the orientation have high strength and little structural deterioration due to the absorption / desorption reaction of Li ions, so that the life characteristics are improved. Particularly, it is preferable that the orientation of the graphite crystallites existing inside the fibrous carbonaceous material particles is disturbed. Such fibrous carbonaceous material particles facilitate the absorption / desorption reaction of Li ions from the outer peripheral surface, and not only the life characteristics are improved but also the rapid charge / discharge performance is improved. However, if the graphite crystals of the fibrous carbonaceous material particles are coaxially tubular (onion type), the internal diffusion of lithium ions may be hindered.

The fibrous carbonaceous material particles in which the orientation of the graphite crystallites is radial type are preferably formed from carbonized or graphitized mesophase pitch carbon fibers.

(2) Spherical carbonaceous material particles The average diameter of spherical carbonaceous material particles is 1 to 100 μm.
m, more preferably 2 to 40 μm.

The minor axis / major axis of spherical carbonaceous material particles is
It is desirable to make it 1/10 or more. More preferably,
It is desirable that the shape be close to a true sphere by setting the ratio to 1/2 or more. The spherical carbonaceous material particles are preferably formed from carbonized or graphitized mesophase microspheres.

The orientation of the graphite crystallites of the graphite structure of the spherical carbonaceous material particles can be radial type, lamella type, Brooks-Taylor type in which lamella (thin layer) type and radial type are combined. For the definition of the Brooks-Taylor type, see “Chemi-cal & Physics”.
"Carbon" Vol 4, 1968, p243, and "Carbon" Vol 3, 1965, p18.
5, respectively. It is also known that the orientation is concentric spherical.

A carbonaceous material having a graphite structure region and an amorphous carbon structure region, having a peak in powder X-ray diffraction corresponding to d ₀₀₂ of 0.340 nm or less, and having a true density of 1.8 g / cm ³ or more. Can be produced, for example, by the methods shown in (1) to (3) below.

(1) Graphitizable carbon precursor (for example, petroleum pitch, mesophase pitch made from coal pitch, coke, etc.) and non-graphitizable carbon precursor (for example, isotropic pitch, polyacryl) Nitrile, furfuryl alcohol, furan resin, phenolic resin, cellulose, sugar, polyvinylidene chloride, etc.) 80
The carbonaceous material is produced by heat treatment in the range of 0 to 3000 ° C.

(2) Fe, Co, N is added to the graphitizable carbon precursor or the non-graphitizable carbon precursor.
When a catalyst such as i, Ca, Cr, Mn, Al, or Si is added, and the graphitizable carbon precursor is 1000 to 1,000,
In the case of the non-graphitizable carbon precursor in the range of 2000 ° C., the carbonaceous material is produced by heat treatment in the range of 1500 to 3000 ° C.

(3) Mechanically forming voids (defects) in graphite crystals of natural graphite, artificial graphite, mesophase pitch carbon fibers, graphitized mesophase spherules by acid treatment, ion implantation, vapor phase oxidation treatment, etc. Thus, the carbonaceous material is produced.

For the negative electrode 6, for example, a binder dispersed in a suitable solvent (eg, organic solvent) and the carbonaceous material are mixed, and the obtained suspension is applied to a current collector and dried. rear,
It can be manufactured by pressing. In addition, you may perform a multistage press 2 to 5 times in a press process.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR),
Carboxymethyl cellulose (CMC) or the like can be used.

The blending ratio of the carbonaceous material and the binder is
The carbon material is preferably in the range of 90 to 98% by weight and the binder in the range of 2 to 10% by weight. In particular, the negative electrode 6 preferably has a carbonaceous material content of 5 to 20 mg / cm ² .

As the current collector, for example, copper foil, stainless foil, nickel foil or the like can be used. 4) Electrolyte solution The non-aqueous electrolyte solution is prepared by dissolving an electrolyte in a non-aqueous solvent.

The non-aqueous solvent may be a non-aqueous solvent known as a solvent for lithium secondary batteries, and is not particularly limited, but it has a melting point lower than that of ethylene carbonate (EC) and the ethylene carbonate and is a donor. It is preferable to use a non-aqueous solvent mainly composed of a mixed solvent with one or more non-aqueous solvents having a number of 18 or less (hereinafter referred to as a second solvent). Such a non-aqueous solvent has the advantages that it is stable with respect to the carbonaceous material with a developed graphite structure that constitutes the negative electrode, that reductive decomposition or oxidative decomposition of the electrolytic solution does not easily occur, and that it has high conductivity.

The non-aqueous electrolytic solution containing only ethylene carbonate has an advantage that it is difficult to be reductively decomposed with respect to the graphitized carbonaceous material, but has a high melting point (39 ° C. to 40 ° C.).
(° C) High viscosity makes it unsuitable for secondary batteries operating at room temperature because of its low electrical conductivity. The second solvent mixed with ethylene carbonate makes the mixed solvent have a lower viscosity than the ethylene carbonate and improves the conductivity. Further, by using a second solvent having a donor number of 18 or less (however, the donor number of ethylene carbonate is 16.4), it becomes difficult for the ethylene carbonate to be selectively solvated with lithium ions, and a graphite structure is developed. It is considered that the reduction reaction of the second solvent with respect to the carbonaceous material is suppressed. Further, by setting the number of donors of the second solvent to 18 or less, the oxidative decomposition potential becomes 4 relative to the lithium electrode.
It also has an advantage that a lithium secondary battery having a high voltage is easily realized and a high voltage can be realized.

As the second type solvent, for example, chain carbon is preferable, and among them, dimethyl carbonate (DM
C), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, or propylene carbonate (P
C), γ-butyrolactone (γ-BL), acetonitrile (AN), ethyl acetate (EA), propyl formate (P
F), methyl formate (MF), toluene, xylene or methyl acetate (MA). These second solvents can be used alone or in the form of a mixture of two or more kinds. In particular, it is more preferable that the second type solvent has a donor number of 16.5 or less.

The viscosity of the second solvent is 2 at 25 ° C.
It is preferably 8 cp or less. The blending amount of the ethylene carbonate in the mixed solvent is 10 to 10 by volume.
It is preferably 80%. If you deviate from this range,
There is a possibility that charge and discharge efficiency may decrease due to decrease in conductivity or decomposition of solvent. A more preferable blending amount of ethylene carbonate is 20 to 75% by volume. By increasing the blending amount of ethylene carbonate in the non-aqueous solvent to 20% by volume or more, solvation of ethylene carbonate to lithium ions is facilitated, so that the effect of suppressing decomposition of the solvent can be improved.

A more preferable composition of the mixed solvent is EC
And MEC, EC and PC and MEC, EC and MEC and DE
C, EC and MEC and DMC, EC and MEC and PC and DE
The volume ratio of MEC in the mixed solvent of C is preferably 30 to 80%. Thus, the volume ratio of MEC is 30
The conductivity can be improved by adjusting the content to -80%, and more preferably to 40-70%. On the other hand, from the viewpoint of suppressing the reductive decomposition reaction of the solvent, the use of an electrolytic solution in which carbon dioxide gas (CO ₂ ) is dissolved is effective in improving the capacity and the cycle life.

Main impurities present in the mixed solvent (non-aqueous solvent) include water and organic peroxides (eg glycols, alcohols, carboxylic acids). It is considered that each of the impurities forms an insulating film on the surface of the graphitized product and increases the interfacial resistance of the electrode. Therefore, the cycle life and the capacity may be reduced. In addition, self-discharge during storage at high temperature (60 ° C or higher) may increase. Therefore, it is preferable that the impurities are reduced as much as possible in the electrolytic solution containing the non-aqueous solvent. Specifically, the water content is 50 pp
m or less, and the organic peroxide content is preferably 1000 ppm or less.

As the electrolyte contained in the non-aqueous electrolyte, for example, lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium arsenide hexafluoride ( LiAsF
₆ ), lithium trifluorometasulfonate (LiCF
₃ SO ₃ ), lithium salt (electrolyte) such as bistrifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₂ ) ₂ ] and the like. Above all, LiPF ₆ , LiB
It is preferable to use F ₄ and LiN (CF ₃ SO ₂ ) ₂ .

The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / 1. In addition, although the example applied to the cylindrical lithium secondary battery has been described in FIG. 1 described above, the present invention can be similarly applied to the prismatic lithium secondary battery. Further, the electrode group housed in the battery container is not limited to the spiral shape, and may have a configuration in which a plurality of positive electrodes, separators and negative electrodes are laminated in this order.

Another lithium secondary battery according to the present invention is a lithium secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolytic solution. The carbonaceous material is the element M (provided that the element M is
Contains at least one element selected from Mg, Al, Si, Ca, Sn and Pb) and has a powder X-ray diffraction pattern of d ₀₀₂ of 0.344 nm or less (provided that d ₀₀₂
Has a peak corresponding to the (002) plane spacing).

The secondary battery can be applied to the cylindrical lithium secondary battery having the structure shown in FIG. Further, it can be applied to a prismatic lithium secondary battery having a structure in which separators are respectively interposed between a plurality of negative electrodes and a plurality of positive electrodes to form a laminated body, and the laminated body is housed in a rectangular cylindrical container with a bottom. it can.

As the positive electrode, the separator and the electrolytic solution, the same ones as described above can be used. 1) Negative Electrode The negative electrode contains a carbonaceous material that absorbs and releases lithium ions. The carbonaceous material is Mg, Al, Si, Ca, Sn
And one or more elements M (heterogeneous element M) selected from Pb and 0.34n in powder X-ray diffraction
It has a peak corresponding to d ₀₀₂ of m or less. Note that d
_{Reference numeral 002} indicates the plane spacing of the (002) plane of the graphite crystallite.

The measurement and definition of the interplanar spacing d ₀₀₂ of the (002) plane by powder X-ray diffraction are as described above. The carbonaceous material has a peak corresponding to d ₀₀₂ of 0.344 nm or less in powder X-ray diffraction. It is difficult to improve the discharge capacity of a lithium secondary battery with a carbonaceous material that does not have such a peak. The carbonaceous material may have only a peak corresponding to d ₀₀₂ of 0.344 nm or less in powder X-ray diffraction, but d ₀₀₂ exceeding 0.344 nm
There may be a peak corresponding to. However, in the carbonaceous material having a peak corresponding to d ₀₀₂ exceeding 0.344 nm, the proportion of d ₀₀₂ of 0.344 nm or less is lowered, the degree of graphitization is lowered, and the true density may be lowered. When the true density decreases, the volume specific capacity (m
Ah / cc) may decrease. A more preferable carbonaceous material has a peak in powder X-ray diffraction corresponding to d ₀₀₂ of 0.340 nm or less. A more preferable carbonaceous material has a powder X-ray diffraction of 0.3354 to 0.344.
nm (preferably 0.3354 to 0.340 nm) d
_It has a peak corresponding to ₀₀₂ .

It is presumed that the element M exists between the graphite crystallites of the carbonaceous material and between the hexagonal network plane layers of the graphite crystallites. This element M has a larger amount of lithium ion storage / release per unit volume than the carbonaceous material. Therefore, when the carbonaceous material having the specific peak described above contains the element M, the capacity of the negative electrode can be improved. Above all, it is preferable to use Si, Pb, Al, and Ca. When the carbonaceous material contains two or more kinds of elements M, it is preferable to use the element M composed of Si and Al or the element M composed of Ca and Mg.

The carbonaceous material preferably contains the element M in an atomic ratio (the number of atoms of the element M with respect to the number of carbon atoms in the carbonaceous material) of 0.1 to 10%. When the content of the element M in the carbonaceous material is less than 0.1% in atomic ratio, the content of the element M is small, so that the effect of increasing the capacity of the negative electrode by introducing the element M may be insufficient. On the other hand, when the content of the element M exceeds 10% in atomic ratio, a large amount of metal carbonized product is generated in the carbonaceous material, and the cycle life may be shortened. A more preferable content is in the range of 1 to 8% in atomic ratio.

The true density of the carbonaceous material is 1.7 g / cm.
It is preferably ³ or more. If the true density of the carbonaceous material is less than 1.7 g / cm ³ , the ratio of d ₀₀₂ of 0.344 nm or less may be reduced, and the volume specific capacity of the negative electrode containing the carbonaceous material may be reduced. The true density of the carbonaceous material is more preferably 2.0 g / cm ³ or more.
The upper limit of the true density is 0.34 for d ₀₀₂ of the carbonaceous material.
It is preferable to set such that those having a thickness of 4 nm or less are present at a high ratio. Further, the upper limit of the true density varies depending on the type and content of the element M contained in the carbonaceous material.

The carbonaceous material can be present in the negative electrode in the form of fibrous particles, spherical particles, or a mixture of fibrous particles and spherical particles. The fibrous carbonaceous material particles include, in addition to carbon fibers, particles obtained by crushing carbon fibers.

(1) Fibrous carbonaceous material particles The average fiber length of the fibrous carbonaceous material particles is 10 to 10.
It is preferably in the range of 0 μm.

The average fiber diameter of the fibrous carbonaceous material particles is
It is preferably in the range of 1 to 20 μm. The specific surface area of the fibrous carbonaceous material particles is 0.1 to ⁵ m ² / g.
Is preferred.

The fibrous carbonaceous material particles have an average fiber length in the range of 10 to 100 μm and an average fiber diameter of 1 to 2.
When it is in the range of 0 μm, it is preferable to set the aspect ratio (fiber length / fiber diameter) in the range of 2 to 10 for the same reason as described above.

Among the above fibrous carbonaceous material particles, the fibrous carbonaceous particles obtained by crushing carbon fibers have an average particle diameter of 1 to 100 μm, more preferably 2
It is desirable to be in the range of -40 μm.

The orientation of graphite crystallites in the graphite structure region of the fibrous carbonaceous material particles is preferably radial. The radial orientation also includes orientations belonging to lamella type and Brooks stella type. Among the fibrous carbonaceous material particles in which the orientation of the graphite crystallites belongs to the radial type, those having an appropriate disorder in the orientation are preferable. The fibrous carbonaceous material particles having an appropriate disorder in the orientation have high strength and little structural deterioration due to the absorption / desorption reaction of Li ions, so that the life characteristics are improved. Particularly, it is preferable that the orientation of the graphite crystallites existing inside the fibrous carbonaceous material particles is disturbed. Such fibrous carbonaceous material particles facilitate the absorption / desorption reaction of Li ions from the outer peripheral surface, and not only the life characteristics are improved but also the rapid charge / discharge performance is improved. However, if the graphite crystals of the fibrous carbonaceous material particles are coaxially tubular (onion type), the internal diffusion of lithium ions may be hindered.

Further, the fibrous carbonaceous material particles in which the orientation of the graphite crystallites belongs to the radial type are preferably formed from carbonized or graphitized mesophase pitch carbon fibers.

(2) Spherical carbonaceous material particles The average diameter of spherical carbonaceous material particles is 1 to 100 μm.
m, more preferably 2 to 40 μm.

The minor axis / major axis of spherical carbonaceous material particles is
It is desirable to make it 1/10 or more. More preferably,
It is desirable that the shape be close to a true sphere by setting the ratio to 1/2 or more. The spherical carbonaceous material particles are preferably formed from carbonized or graphitized mesophase microspheres.

The orientation of the graphite crystallites of the graphite structure of the spherical carbonaceous material particles can be radial type, lamella type, or Brooks-Taylor type in which lamella (thin layer) type and radial type are combined. It is also known that the orientation is concentric spherical.

The carbonaceous material is, for example, a graphitizable carbon precursor (eg, petroleum pitch, mesophase pitch made from coal pitch, coke, etc.) or a non-graphitizable carbon precursor (eg, isotropic). Pitch, polyacrylonitrile, furfuryl alcohol, furan resin, phenolic resin, cellulose, sugar, polyvinylidene chloride, etc.) or a mixture of both, and a compound containing the element M is added, and the temperature is in the range of 600 to 3000 ° C. It can be manufactured by heat treatment in. According to such a method, since the carbon precursor can be graphitized to a high degree of graphitization while introducing the element M into the carbon precursor at the heat treatment temperature of 600 to 3000 ° C., the element M is contained and the powder X is contained. It is possible to prepare a carbonaceous material having a peak corresponding to d ₀₀₂ of 0.344 nm or less in line diffraction.

Compounds containing the element M include Mg, A
A single substance of 1, Si, Ca, Sn, or Pb is also included. Among them, it is uniformly dissolved in carbon precursors such as silicon carbide (SiC), magnesium silicide (Mg ₂ Si), aluminum carbide (Al ₄ C ₃ ), tin oxalate, calcium carbide (CaC ₃ ), and lead carbonate. Alternatively, a material that is uniformly mixed with the carbon precursor is preferable.

The reason why the temperature of the heat treatment is limited to the above range is as follows. If the temperature of the heat treatment is less than 600 ° C., the polycondensation reaction of the carbon precursor becomes insufficient, and the graphitization of the carbon precursor may not proceed. On the other hand, if the temperature of the heat treatment exceeds 3000 ° C,
The element M may volatilize, and it may be difficult to introduce the element M into the carbon precursor. From the viewpoint of improving the degree of graphitization of the carbonaceous material, the temperature of the heat treatment is 1500 to
The temperature is preferably 3000 ° C., more preferably 2000 to 3000 ° C.

In such a method, for example, B, Mn, C
A catalyst such as r may be added. When the catalyst is added, the carbonaceous material can be produced at a lower heat treatment temperature.
When the carbonaceous material according to the present invention is produced by this method,
The catalyst may remain in the carbonaceous material. The remaining catalyst does not impair the characteristics of the negative electrode. Further, when a carbonaceous material is produced by using boron (B) as the catalyst and the boron remains in the carbonaceous material, the boron contains a large amount of lithium ion storage / release per unit volume. It is possible to improve the capacity of the negative electrode. Therefore, the carbonaceous material used for the negative electrode of the secondary battery according to the present invention is allowed to contain a trace amount of B, Mn, and Cr.

For the negative electrode, for example, a binder dispersed in a suitable solvent (for example, an organic solvent) and the carbonaceous material are mixed, and the obtained suspension is applied to a current collector and dried. ,
It can be manufactured by pressing. In addition, you may perform a multistage press 2 to 5 times in a press process.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR),
Carboxymethyl cellulose (CMC) or the like can be used.

The mixing ratio of the carbonaceous material and the binder is
The carbon material is preferably in the range of 90 to 98% by weight and the binder in the range of 2 to 10% by weight. In particular, the negative electrode 6 preferably has a carbonaceous material content of 5 to 20 mg / cm ² .

As the current collector, for example, copper foil, stainless steel foil, nickel foil or the like can be used. The negative electrode provided in the lithium secondary battery according to the present invention has a graphite structure region and an amorphous carbon structure region, and has a powder X-ray diffraction peak corresponding to d ₀₀₂ of 0.340 nm or less,
In addition, it includes a carbonaceous material having a true density of 1.8 g / cm ³ or more. Such a negative electrode can dramatically improve the capacity per unit volume (for example, 900 mAh / cc or more). Therefore, the lithium secondary battery including the negative electrode can significantly improve the discharge capacity and the discharge cycle life. It is assumed that this is due to the following mechanism.

That is, the powder X-ray diffraction was 0.340 nm.
A carbonaceous material having a peak corresponding to the following d ₀₀₂ and having a true density of 1.8 g / cm ³ or more has a graphite structure region and an amorphous carbon structure region coexisting at an appropriate ratio, and the graphite proportion of 0.340nm following d ₀₀₂ occupying the d ₀₀₂ of the structural region is high. Since such a carbonaceous material can significantly improve the diffusion rate of lithium ions in the graphite structure region, the amorphous carbon structure region can contribute to the occlusion / release of lithium ions. A carbonaceous material that does not have such a peak even if it has an amorphous carbon structure region has a low graphitization degree in the graphite structure region and a slow diffusion rate of lithium ions in the graphite structure region. Almost no amorphous carbon structural regions can be involved in the release. Since the negative electrode containing such a carbonaceous material has a small amount of insertion and extraction of lithium ions, the capacity per unit volume decreases. In addition, the lithium secondary battery including the negative electrode has poor charge / discharge efficiency. Since a large amount of lithium ions can be stored in the amorphous carbon structure region, if the amorphous carbon structure region of the carbonaceous material can be used as a lithium ion site as in the present invention, lithium ion storage per unit volume of the negative electrode is possible. The amount of release can be increased. Further, since the expansion / contraction portion of the carbonaceous material accompanying the occlusion / release of lithium ions can be absorbed in the amorphous carbon structure region, the graphite structure of the carbonaceous material collapses in the negative electrode as the charge / discharge cycle progresses. Can be suppressed, and the decrease in discharge capacity due to the progress of charge / discharge cycles can be suppressed to a low level. As a result, the lithium secondary battery including the negative electrode can dramatically improve the discharge capacity and the charge / discharge cycle life. In addition, since the lithium secondary battery has a high speed of absorbing and releasing lithium ions in the negative electrode, it is possible to improve the initial charge and discharge efficiency.

By forming a void having a diameter of 0.1 to 20 nm by the small-angle X-ray scattering method in the amorphous carbon structure region of the carbonaceous material, it is possible to increase the lithium ion storage / release amount in the amorphous carbon structure region. it can. As a result, the discharge capacity of the lithium secondary battery provided with the negative electrode containing such a carbonaceous material can be dramatically improved, and thus the charge / discharge cycle life can be further improved.

Further, the amorphous carbon structure region of the carbonaceous material has d ₀₀₂ of 0.370 nm or more,
It is possible to increase the lithium ion storage / release amount in the amorphous carbon structure region. As a result, the discharge capacity of the lithium secondary battery provided with the negative electrode containing such a carbonaceous material can be dramatically improved, and thus the charge / discharge cycle life can be further improved.

Further, a void having a diameter of 0.1 to 20 nm is formed by a small angle X-ray scattering method in the amorphous carbon structure region of the carbonaceous material, and this region has a surface spacing d ₀₀₂ of 0.370 nm or more. This can increase the lithium ion storage / release amount in the amorphous carbon structure region. As a result, the discharge capacity of the lithium secondary battery provided with the negative electrode containing such a carbonaceous material can be dramatically improved, and thus the charge / discharge cycle life can be further improved.

By the way, the fibrous carbonaceous material particles in which the graphite crystallites have a radial orientation can store and release lithium ions not only in the cross section but also in the outer peripheral surface. The amount of occlusion and release can be improved. The radial type fibrous carbonaceous material particles have the above-described graphite structure region and amorphous carbon structure region, and have a d of 0.340 nm or less in powder X-ray diffraction.
There is a peak corresponding to ₀₀₂ and the true density is 1.8g / c
By forming the carbonaceous material of m ³ or more, the lithium ion occlusion / release rate and the occlusion / release amount of the radially oriented fibrous carbonaceous material particles can be effectively improved. Therefore, the lithium secondary battery provided with the negative electrode containing such carbonaceous material particles can dramatically improve the discharge capacity during rapid charge / discharge.

Another lithium secondary battery according to the present invention is an element M (provided that M is at least one element selected from Mg, Al, Si, Ca, Sn and Pb).
And a negative electrode containing a carbonaceous material containing a peak indicating that in the powder X-ray diffraction, the interplanar spacing d ₀₀₂ of the (002) plane is 0.344 nm or less.
A lithium secondary battery equipped with such a negative electrode can dramatically improve the discharge capacity, ensure a high capacity even during rapid charge / discharge, and improve the charge / discharge cycle life. You can It is assumed that this is due to the following mechanism.

That is, in powder X-ray diffraction, 0.34
Since many carbonaceous materials having a peak corresponding to d ₀₀₂ of 4 nm or less are 0.344 nm or less in the interplanar spacing d ₀₀₂ , the diffusion rate of lithium ions can be improved. Therefore, the carbonaceous material can increase the proportion of the element M that can contribute to the lithium ion storage / release reaction. Further, the carbonaceous material has a high true density because the crystallite having a developed graphite structure serves as a skeleton. Therefore, such a negative electrode has a LiC in the graphite crystal structure region.
_Since lithium ions can be occluded rapidly until ₆ is formed, and a large amount of lithium ions can be occluded by the element M, the weight specific capacity (mAh / g) and volume specific capacity (mAh / cc) are It can be greatly improved as compared with the negative electrode in which the element M is introduced into the carbon material in which no peak is detected. As a result, the lithium secondary battery including the negative electrode is
The discharge capacity can be dramatically improved, and the charge / discharge cycle life can be improved. Further, in the lithium secondary battery, since the lithium ion storage / release speed of the negative electrode is high, the rapid charge / discharge efficiency can be improved.

Further, by setting the content of the element M in the carbonaceous material in the range of 0.1 to 10% in atomic ratio, the effect of increasing the discharge capacity by adding the element M to the carbonaceous material is effective. Therefore, the discharge capacity of the lithium secondary battery can be further improved.

Further, the fibrous carbonaceous material particles in which the orientation of the graphite crystallite is radial type are obtained by the above-mentioned carbonaceous material, that is, the powder X-ray diffraction has a peak corresponding to d ₀₀₂ of 0.344 nm or less. By forming the carbonaceous material containing the element M, it is possible to effectively improve the lithium ion storage / release rate and storage / release amount of the fibrous carbonaceous material particles in the radial orientation. Therefore, the lithium secondary battery provided with the negative electrode containing such carbonaceous material particles can dramatically improve the discharge capacity during rapid charge / discharge.

[0093]

Embodiments of the present invention will now be described in detail with reference to FIG. Example 1 First, lithium cobalt oxide (LiCoO ₂ ) powder 9
1% by weight of acetylene black 3.5% by weight, graphite 3.5% by weight and ethylene propylene diene monomer powder 2% by weight and toluene were added and mixed together, and applied on an aluminum foil (30 μm) current collector, followed by pressing. By doing so, a positive electrode was produced.

Further, 20% of a phenol resin was added to mesophase pitch obtained from petroleum pitch, which was spun, infusibilized, carbonized at 600 ° C. in an argon gas atmosphere, the average particle size was 11 μm, and the particle size was 1 μm. 90 μ% or more in the range of ˜80 μm and a particle size of 0.5 μ
The particles of m or less are appropriately pulverized so as to be small (5% or less). Then, fibrous carbonaceous material particles were produced by graphitizing at 2700 ° C. in an inert gas atmosphere.

The obtained fibrous carbonaceous material particles had an average fiber diameter of 7 μm, an average fiber length of 40 μm, and an average particle diameter of 20 μm. 9 in the range of 1-80 μm in particle size distribution
0% by volume or more was present, and the particle size distribution of particles having a particle size of 0.5 μm or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g. The true density is
It was 2.0 g / cm ³ . By X-ray diffraction (002)
From the lattice image, it was confirmed that the fine structure of the fibrous carbonaceous material particles coexisted with the graphite structure region and the amorphous carbon structure region. When the diameter of a large number of fine voids existing in the amorphous carbon structure region was measured by the small angle X-ray scattering method, the diameter was 0.5 to 20 nm. The carbonaceous material particles have a powder X-ray diffraction pattern of 0.336 nm.
A peak corresponding to d ₀₀₂ of, 0.370Nm of d ₀₀₂
A peak corresponding to was obtained. This 0.336 nm d
_The peak corresponding to ₀₀₂ is considered to be due to the graphite structure region of the carbonaceous material particles. On the other hand, d of 0.370 nm
_The peak corresponding to ₀₀₂ is considered to be due to the amorphous carbon structure region of the carbonaceous material. Furthermore, when the cross section of the fibrous carbonaceous material particles was observed by SEM (scanning electron microscope), the orientation of the graphite crystallites of the particles belonged to the radial type. However, there was some disorder in the orientation.

Next, 96.7% by weight of the mesophase pitch fibrous carbonaceous material particles were mixed with 2.2% by weight of styrene-butadiene rubber and 1.1% by weight of carboxymethylcellulose, and this was used as a copper foil as a current collector. Apply
A negative electrode was produced by drying and pressing.

The positive electrode, the separator made of a polyethylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located outside to prepare an electrode group.

Furthermore, lithium hexafluorophosphate (LiP
F ₆ ) is a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (mixing volume ratio 5
A non-aqueous electrolyte was prepared by dissolving 1.0 mol / 1 in 0:50).

The electrode group and the electrolytic solution were respectively housed in a bottomed cylindrical container made of stainless steel, and the cylindrical lithium secondary battery shown in FIG. 1 was assembled. Example 2 The cylindrical lithium secondary battery shown in FIG. 1 was assembled in the same configuration as in Example 1 except that the carbonaceous material described below was used.

Natural graphite was finely pulverized to an average particle size of 1 μm or less, and then a mixture prepared by adding 20% of isotropic pitch was subjected to carbonization treatment and pulverization treatment at 1100 ° C. to obtain an average particle size. To form spherical carbonaceous material particles having a diameter of 15 μm.

The true density of the carbonaceous material particles is 2.2 g / c.
It was m ³ . From the (002) lattice image by X-ray diffraction,
It was confirmed that the fine structure of the carbonaceous material particles was composed of a graphite structure region and an amorphous carbon structure region. When the diameter of a large number of fine voids existing in the amorphous carbon structure region was measured by the small angle X-ray scattering method, the diameter was 0.5 to 20 nm. The carbonaceous material particles have a peak in powder X-ray diffraction corresponding to d ₀₀₂ of 0.3358 nm,
A peak corresponding to d ₀₀₂ of 0.380 nm was obtained.
The peak corresponding to d ₀₀₂ at 0.3358 nm is considered to be due to the graphite structure region of the carbonaceous material particles.
On the other hand, the peak corresponding to d ₀₀₂ at 0.380 nm is considered to be due to the amorphous carbon structure region of the carbonaceous material particles. Furthermore, when the spherical carbonaceous material particles were observed by SEM, the graphite crystallites of the particles were not oriented, and the orientation was random type.

Example 3 Example 1 except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

20% of a phenol resin was added to mesophase pitch obtained from petroleum pitch, which was spun, infusibilized, carbonized at 600 ° C. under an argon gas atmosphere, the average particle size was 11 μm, and the particle size was 1 to 80 μm. In this range, 90% by volume or more is present, and particles having a particle size of 0.5 μm or less are appropriately pulverized so as to be small (5% or less). Then, fibrous carbonaceous material particles were produced by graphitizing at 2700 ° C. in an inert gas atmosphere.

The obtained fibrous carbonaceous material particles had an average fiber diameter of 7 μm, an average fiber length of 40 μm, and an average particle diameter of 20 μm. 9 in the range of 1-80 μm in particle size distribution
0% by volume or more was present, and the particle size distribution of particles having a particle size of 0.5 μm or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g. The true density is
It was 2.0 g / cm ³ . By X-ray diffraction (002)
From the lattice image, it was confirmed that the fine structure of the fibrous carbonaceous material particles coexisted with the graphite structure region and the amorphous carbon structure region. When the diameter of a large number of fine voids existing in the amorphous carbon structure region was measured by the small angle X-ray scattering method, the diameter was 0.5 to 20 nm. The carbonaceous material particles have a particle size of 0.3357 n in powder X-ray diffraction.
A peak corresponding to d ₀₀₂ of m was obtained. This 0.33
The peak corresponding to d ₀₀₂ at 57 nm is considered to be due to the graphite structure region of the carbonaceous material particles. Furthermore, when the cross section of the fibrous carbonaceous material particles was observed by SEM, the orientation of the graphite crystallites of the particles belonged to the radial type. However, there was some disorder in the orientation.

Example 4 Example 1 was repeated except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

Natural graphite was finely pulverized to an average particle size of 1 μm or less, and then a mixture prepared by adding 20% of isotropic pitch was subjected to carbonization treatment and pulverization treatment at 1100 ° C. to obtain an average particle size. To form spherical carbonaceous material particles having a diameter of 15 μm.

The true density of the carbonaceous material particles is 2.2 g / c.
It was m ³ . From the (002) lattice image by X-ray diffraction,
It was confirmed that the fine structure of the carbonaceous material particles was composed of a graphite structure region and an amorphous carbon structure region. When the diameter of a large number of fine voids existing in the amorphous carbon structure region was measured by the small angle X-ray scattering method, the diameter was 0.5 to 20 nm. Further, the carbonaceous material particles had a peak corresponding to d ₀₀₂ of 0.3356 nm in powder X-ray diffraction. The peak corresponding to d ₀₀₂ at 0.3356 nm is considered to be due to the graphite structure region of the carbonaceous material particles. Furthermore, when the spherical carbonaceous material particles were observed by SEM, the graphite crystallites of the particles were not oriented, and the orientation was random type.

Comparative Example 1 The fine structure was composed only of the graphite structure region, had a peak in powder X-ray diffraction corresponding to d ₀₀₂ of 0.3354 nm, and the length of the c-axis crystallite determined by powder X-ray diffraction. Lc of 100 nm or more, true density of 2.25 g / cm
^The cylindrical lithium secondary battery shown in FIG. 1 was assembled in the same configuration as in Example 1 except that the artificial graphite powder of ³ was used as the carbonaceous material of the negative electrode.

Comparative Example 2 Example 1 was repeated except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

The carbonaceous material was prepared by carbonizing an epoxy novolac resin at 1100 ° C. The true density of the carbonaceous material was 1.55 g / cm ³ . From the (002) lattice image by X-ray diffraction, it was confirmed that the fine structure of the carbonaceous material was composed of a graphite structure region and an amorphous carbon structure region. The diameter of many voids existing in the amorphous carbon structure region was measured by the small angle X-ray scattering method, and the diameter was 1 nm. Further, in the carbonaceous material, a peak corresponding to d ₀₀₂ of 0.380 nm was obtained in powder X-ray diffraction. The crystallite length Lc in the C-axis direction by powder X-ray diffraction was 1 nm.

With respect to the obtained secondary batteries of Examples 1 to 5 and Comparative Examples 1 and 2, 2.5 A up to 4.2 V at a charging current of 1 A.
After charging for an hour, a charge / discharge cycle test of discharging at 1 A to 2.7 V was performed. From the results, for each secondary battery, the initial charge / discharge efficiency, the discharge capacity at the first cycle and the 30
The capacity retention rate (relative to the discharge capacity at the first cycle) at 0 cycle was measured, and the results are shown in Table 1 below.

[0112]

[Table 1]

As is clear from Table 1, it has a graphite structure region and an amorphous carbon structure region, and has a powder X-ray diffraction pattern of 0.34.
The secondary batteries of Examples 1 to 4 each having a negative electrode containing a carbonaceous material having a peak corresponding to d ₀₀₂ of 0 nm or less and having a true density of 1.8 g / cm ³ or more had initial charge / discharge efficiency and discharge. It can be seen that the capacity and the capacity retention rate after 300 cycles are high.

On the other hand, the secondary battery of Comparative Example 1 provided with the negative electrode including the carbonaceous material having the fine structure only of the graphite structure region and having the peak corresponding to d ₀₀₂ of 0.3354 nm in the powder X-ray diffraction was Although the initial charge / discharge efficiency is excellent, it can be seen that the discharge capacity and the capacity retention rate are lower than those in Examples 1 to 4. On the other hand, the fine structure is composed of a graphite structure region and an amorphous carbon structure region, has a peak in powder X-ray diffraction corresponding to d ₀₀₂ of 0.380 nm, and has a true density of 1.55 g /
It can be seen that the secondary battery of Comparative Example 2 including the negative electrode containing the carbonaceous material of cm ³ has lower initial charge / discharge efficiency, discharge capacity, and capacity retention rate than Examples 1 to 4.

Example 5 First, lithium cobalt oxide (LiCoO ₂ ) powder 9 was used.
1% by weight of acetylene black 3.5% by weight, graphite 3.5% by weight and ethylene propylene diene monomer powder 2% by weight and toluene were added and mixed together, and applied on an aluminum foil (30 μm) current collector, followed by pressing. By doing so, a positive electrode was produced.

Further, fine powder of silicon carbide (SiC) was added to mesophase pitch obtained from petroleum pitch, and after uniformly dispersing, spinning, infusibilization, and carbonization at 600 ° C. in an inert gas atmosphere. And pulverized so that the average particle size is 15 μm and 90 vol% or more is present in the range of particle size 1 to 80 μm. Then, fibrous carbonaceous material particles were produced by graphitizing at 2600 ° C. under an inert gas atmosphere and under pressure.

The obtained mesophase pitch fibrous carbonaceous material particles contained silicon (Si) in an atomic ratio of 8%. The true density of the fibrous carbonaceous material particles is 2.1.
It was 0 g / cm ³ . The fibrous carbonaceous material particles had a peak in powder X-ray diffraction corresponding to d ₀₀₂ of 0.3367 nm. In addition, powder X-ray diffraction was performed using CuKα as an X-ray source and high-purity silicon as a standard substance, and the half-width half-point method specified in the Gakshin method was determined from the diffraction peak position and half-width of the obtained diffraction pattern. The crystallite length Lc in the C-axis direction of the graphite structure region was calculated by, and it was 35 nm. In addition, it was confirmed by SEM observation of the cross section that the orientation of the graphite crystallites belonged to the radial type. However, there was some disorder in the orientation. Furthermore, the average fiber diameter is 7μ
m, average fiber length is 40 μm, average particle size is 20 μm
Met. 90% by volume in the range of 1-80 μm in particle size distribution
The above was present, and the particle size distribution of particles having a particle size of 0.5 μm or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g. The half-width half-point method is described in the document "Tanso (carbon)", 1963, p25.

Next, 96.7% by weight of the mesophase pitch type fibrous carbonaceous material particles were mixed with 2.2% by weight of styrene-butadiene rubber and 1.1% by weight of carboxymethyl cellulose, and this was used as a copper foil as a current collector. Apply
A negative electrode was produced by drying and pressing. The packing density of the obtained negative electrode was 1.4 g / cm ³ .

The positive electrode, the separator made of a polyethylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located outside to form an electrode group.

Furthermore, lithium hexafluorophosphate (LiP
F ₆ ) is a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (mixing volume ratio 1:
1 mol / 1 was dissolved in 1) to prepare a non-aqueous electrolytic solution.

The electrode group and the electrolytic solution were respectively housed in a bottomed cylindrical container made of stainless steel, and the cylindrical lithium secondary battery shown in FIG. 1 was assembled. Example 6 Example 5 except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

The carbonaceous material includes mesophase pitch obtained from petroleum pitch and magnesium silicide (Mg ₂ S).
After adding the fine powder of i) and uniformly dispersing it, spinning
Infusibilize, carbonize at 600 ° C in an inert gas atmosphere,
Average particle size is 15 μm, 90 in the range of particle size 1-80 μm
Grind so that more than volume% is present. Then, fibrous carbonaceous material particles produced by graphitizing at 2000 ° C. under an inert gas atmosphere and under pressure were used.

In the fibrous carbonaceous material particles, the content of magnesium (Mg) is 4% in atomic ratio, the content of silicon (Si) is 2% in atomic ratio, and the true density is 2.2 g / cm ³ .
Lc by powder X-ray diffraction was 25 nm. The fibrous carbonaceous material particles had a peak in powder X-ray diffraction corresponding to d ₀₀₂ of 0.3380 nm. Also,
It was confirmed by SEM observation of the cross section that the orientation of the graphite crystallite belonged to the radial type. However, there was some disorder in the orientation. Furthermore, the average fiber diameter was 7 μm, the average fiber length was 40 μm, and the average particle size was 20 μm. In the particle size distribution, 90% by volume or more exists in the range of 1 to 80 μm, and the particle size distribution of particles having a particle size of 0.5 μm or less is 0% by volume.
Met. The specific surface area by the N ₂ gas adsorption BET method is
It was 1.2 m ² / g.

Example 7 Example 5 was repeated except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

The carbonaceous material includes mesophase pitch obtained from petroleum pitch and aluminum carbide (Al ₄ C
₃ ) was added, spun, infusibilized, carbonized at 600 ° C. in an inert gas atmosphere, and pulverized to have an average particle size of 15 μm and 90% by volume or more in the particle size range of 1 to 80 μm. To do. Then, fibrous carbonaceous material particles produced by graphitizing at 2800 ° C. under an inert gas atmosphere and under pressure were used.

The fibrous carbonaceous material particles have an aluminum (Al) content of 8% in atomic ratio and a true density of 2.3.
g / cm ³ , Lc by powder X-ray diffraction was 30 nm. The fibrous carbonaceous material particles have a powder X-ray diffraction of 0.3.
It had a peak corresponding to d ₀₀₂ at 375 nm. In addition, it was confirmed by SEM observation of the cross section that the orientation of the graphite crystallites belonged to the radial type. However, there was some disorder in the orientation. Furthermore, the average fiber diameter is 7μ
m, average fiber length is 40 μm, average particle size is 20 μm
Met. 90% by volume in the range of 1-80 μm in particle size distribution
The above was present, and the particle size distribution of particles having a particle size of 0.5 μm or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g.

Example 8 Example 5 was repeated except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

For the carbonaceous material, fine powder of tin oxalate was added to mesophase pitch obtained from petroleum pitch, and after uniformly dispersing, spinning, infusible, and 600 ° C. in an inert gas atmosphere. Is carbonized with an average particle size of 15 μm
Then, it is pulverized so that 90% by volume or more exists in the range of particle size 1 to 80 μm. Then, fibrous carbonaceous material particles produced by graphitizing at 2000 ° C. under an inert gas atmosphere and under pressure were used.

The fibrous carbonaceous material particles are tin (S
The content of n) is 5% in atomic ratio, and the true density is 2.3 g / c.
m ³ , Lc by powder X-ray diffraction was 25 nm. The fibrous carbonaceous material particles have a powder X-ray diffraction pattern of 0.3390.
It had a peak corresponding to d ₀₀₂ of nm.
In addition, it was confirmed by SEM observation of the cross section that the orientation of the graphite crystallites belonged to the radial type. However, there was some disorder in the orientation. Furthermore, the average fiber diameter was 7 μm, the average fiber length was 40 μm, and the average particle size was 20 μm. In the particle size distribution, 90% by volume or more was present in the range of 1 to 80 μm, and the particle size distribution of particles having a particle size of 0.5 μm or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g.

Example 9 Example 5 was repeated except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

To the above-mentioned carbonaceous material, after adding calcium carbide (CaC ₃ ) to mesophase pitch obtained from petroleum pitch, spinning and infusibilization were conducted under an inert gas atmosphere.
Carbonized at 600 ℃, average particle size 15μm, particle size 1 ~
Grind so that 90% by volume or more exists in the range of 80 μm. After that, under an inert gas atmosphere and under pressure, 2
Fibrous carbonaceous material particles produced by graphitizing at 000 ° C. were used.

In the fibrous carbonaceous material particles, the content of calcium (Ca) is 9% in atomic ratio, and the true density is 2.25.
g / cm ³ , Lc by powder X-ray diffraction was 35 nm. The fibrous carbonaceous material particles have a powder X-ray diffraction of 0.3.
It had a peak corresponding to d ₀₀₂ at 370 nm. In addition, it was confirmed by SEM observation of the cross section that the orientation of the graphite crystallites belonged to the radial type. However, there was some disorder in the orientation. Furthermore, the average fiber diameter is 7μ
m, average fiber length is 40 μm, average particle size is 20 μm
Met. 90% by volume in the range of 1-80 μm in particle size distribution
The above was present, and the particle size distribution of particles having a particle size of 0.5 μm or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g.

Example 10 Example 5 was repeated except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

To the carbonaceous material, fine powder of lead carbonate was added to mesophase pitch obtained from petroleum pitch and dispersed uniformly, and then spun and infusible at 600 ° C. under an inert gas atmosphere. It is carbonized and pulverized so that the average particle size is 15 μm and 90 vol% or more is present in the range of particle size 1 to 80 μm. Then, fibrous carbonaceous material particles produced by graphitizing at 2000 ° C. under an inert gas atmosphere and under pressure were used.

The fibrous carbonaceous material particles are lead (Pb)
Content of 8% in atomic ratio, true density 2.5g / cm
³ , Lc by powder X-ray diffraction was 35 nm. The fibrous carbonaceous material particles have a powder X-ray diffraction of 0.3370 n.
It had a peak corresponding to d ₀₀₂ of m. In addition, it was confirmed by SEM observation of the cross section that the orientation of the graphite crystallites belonged to the radial type. However, there was some disorder in the orientation. Furthermore, the average fiber diameter was 7 μm, the average fiber length was 40 μm, and the average particle size was 20 μm. In the particle size distribution, 90% by volume or more was present in the range of 1 to 80 μm, and the particle size distribution of particles having a particle size of 0.5 μm or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g.

Example 11 Example 5 was repeated except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

To the carbonaceous material, fine powder of silicon carbide and aluminum carbide were added to mesophase pitch obtained from petroleum pitch, and after uniformly dispersing, spinning, infusible, and 600 Carbonized at ℃, average particle size 15μm, 90% by volume in the range of particle size 1-80μm
Grind so that the above exists. Then, fibrous carbonaceous material particles produced by graphitizing at 2000 ° C. under an inert gas atmosphere and under pressure were used.

The fibrous carbonaceous material particles are made of silicon (S
The content of i) is 10% in atomic ratio, and aluminum (A
The content of 1) is 10% in atomic ratio and the true density is 2.2 g.
/ Cm ³ . The carbonaceous material particles are powder X
It had a peak in line diffraction corresponding to d ₀₀₂ of 0.3370 nm. Furthermore, Lc by powder X-ray diffraction was 35 nm. When the cross section of the fibrous carbonaceous material particles was observed by SEM, the orientation of the graphite crystallites of the fibrous carbonaceous material particles belonged to the radial type. However, there was some disorder in the orientation. Furthermore, the average fiber diameter was 7 μm, the average fiber length was 40 μm, and the average particle size was 20 μm. 1-80 in particle size distribution
90 volume% or more exists in the range of μm, and the particle size is 0.5μ.
The particle size distribution of particles of m or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g.

Comparative Example 3 Example 5 was repeated except that the carbonaceous material described below was used.
The cylindrical lithium secondary battery shown in FIG. 1 and having the same structure as described above was assembled.

As the carbonaceous material, mesophase pitch obtained from petroleum pitch was infusibilized, carbonized at 600 ° C. in an inert gas atmosphere, the average particle size was 15 μm, and the volume was 90 volume in the range of 1 to 80 μm. Grind so that more than 100% is present. Then, fibrous carbonaceous material particles produced by graphitizing at 2600 ° C. under an inert gas atmosphere and under pressure were used.

The fibrous carbonaceous material particles did not contain the element M, had a true density of 2.2 g / cm ³ and an Lc by powder X-ray diffraction of 35 nm. The fibrous carbonaceous material particles had a peak in powder X-ray diffraction corresponding to d ₀₀₂ of 0.3375 nm. Also, the SEM of the cross section
It was confirmed by observation that the orientation of the graphite crystallite belongs to the radial type. However, since there was some disorder in the orientation, there were no missing parts in the fiber. Furthermore, the average fiber diameter is 7
μm, average fiber length is 40 μm, average particle size is 20 μm
It was m. In the particle size distribution, 90% by volume or more was present in the range of 1 to 80 μm, and the particle size distribution of particles having a particle size of 0.5 μm or less was 0% by volume. The specific surface area according to the N ₂ gas adsorption BET method was 1.2 m ² / g.

Comparative Example 4 A novolac resin was produced by carbonizing at 1100 ° C., the true density was 1.6 g / cm ³ , and the powder X-ray diffraction had a peak corresponding to 0.380 nmd ₀₀₂ .
The above-described cylindrical lithium secondary battery shown in FIG. 1 was assembled with the same configuration as in Example 5 except that a carbonaceous material having an Lc of 1 nm by powder X-ray diffraction was used.

Comparative Example 5 Silicon (Si) was contained in an atomic ratio of 6%, and the true density was 1.7.
X-ray powder diffraction d ₀₀₂ of 0.349 nm at g / cm ^3.
1 has the same configuration as that of Example 5 except that a vapor-grown carbonaceous material having a peak corresponding to No. 1 and having an Lc by powder X-ray diffraction of 2.5 nm is used as the carbonaceous material. A lithium secondary battery was assembled.

Comparative Example 6 The cylindrical lithium secondary battery shown in FIG. 1 was assembled in the same configuration as in Example 5 except that the lithium alloy negative electrode made of lithium aluminum (LiAl) was used.

Obtained Examples 5 to 11 and Comparative Examples 3 to 6
The secondary battery of No. 1 was charged with a charging current of 1.5 A to 4.2 V for 2 hours, and then subjected to a charge / discharge cycle test in which it was discharged to 2.7 V at 1.5 A.
The capacity retention rate at the 500th cycle (relative to the discharge capacity at the 1st cycle) was determined, and the results are shown in Table 2 below.

[0146]

[Table 2]

As is clear from Table 2, Mg, Al, S
Examples 5 to 5 provided with a negative electrode containing a carbonaceous material containing one or more elements M selected from i, Ca, Sn and Pb, and having a peak corresponding to d ₀₀₂ of 0.344 nm or less in powder X-ray diffraction The secondary battery of 11 has a high discharge capacity,
Moreover, it can be seen that the capacity retention rate after 500 cycles is high.

On the other hand, the powder X-ray diffraction showed 0.344n.
A secondary battery of Comparative Example 3 having a negative electrode containing a carbonaceous material which does not contain the element M, though having a peak corresponding to d ₀₀₂ of m or less, and a peak corresponding to d ₀₀₂ of 0.380 nm in powder X-ray diffraction. Comparative Example 5 including the secondary battery of Comparative Example 4 including the negative electrode including the carbonaceous material and the negative electrode including the carbonaceous material including Si and having a peak corresponding to d ₀₀₂ of 0.349 nm in powder X-ray diffraction. It can be seen that the secondary battery of No. 2 has lower discharge capacity and capacity retention rate than those of Examples 5 to 11. On the other hand, although the secondary battery of Comparative Example 6 including the negative electrode made of a lithium alloy has a higher discharge capacity than that of Examples 5 to 11, it has a remarkably low capacity retention ratio after 500 cycles.

[0149]

As described in detail above, according to the present invention, it is possible to provide a lithium secondary battery having improved initial charge / discharge efficiency, discharge capacity and cycle life.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a lithium secondary battery according to the present invention.

FIG. 2 is a schematic diagram showing an example of a fine structure of a carbonaceous material contained in the negative electrode of the lithium secondary battery according to the present invention.

FIG. 3 is a schematic view showing an example of fibrous carbonaceous material particles contained in the negative electrode of the lithium secondary battery according to the present invention.

[Explanation of symbols]

1 ... Container, 3 ... Electrode group, 4 ... Positive electrode, 5 ... Separator, 6
… Negative electrode, 8… Sealing plate.

Continuation of front page (56) References Japanese Patent Laid-Open No. 6-119923 (JP, A) Japanese Patent Laid-Open No. 6-187972 (JP, A) Japanese Patent Laid-Open No. 3-263768 (JP, A) Japanese Patent Laid-Open No. 5-182668 (JP) , A) JP 4-126374 (JP, A) JP 7-73898 (JP, A) JP 5-217604 (JP, A) JP 5-335016 (JP, A) JP 5-89879 (JP, A) JP 8-104510 (JP, A) JP 6-168725 (JP, A) JP 8-231273 (JP, A) JP 9-204918 (JP, A) JP-A-6-111818 (JP, A) JP-A-7-192724 (JP, A) JP-A-7-326343 (JP, A) JP-A-7-201317 (JP, A) JP-A-6- -318459 (JP, A) International Publication 97/018160 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/58 C01B 31/02 101 C01B 31/04 101 H01M 4 / 02 H01M 10/40 D01F 9/145

Claims (7)

(57) [Claims] 1. A lithium secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolyte, wherein the carbonaceous material of the negative electrode has an amorphous carbon structure region and It has a graphite structure region and d of 0.34 nm or less in powder X-ray diffraction.
₀₀₂ (however, the above-mentioned d ₀₀₂ indicates the spacing between (002) planes), and the true density is 2 to 2.
It is 2 g / cm ³ , and a lithium secondary battery is characterized in that voids having a diameter of 0.1 to 20 nm are present in the amorphous carbon structure region by a small angle X-ray scattering method. 2. The carbonaceous material has d ₀₀₂ of 0.37 nm or more in the amorphous carbon structure region (provided that the d ₀₀₂ indicates a plane spacing of (002) planes). 1. The lithium secondary battery according to 1. 3. The diameter of the void according to the small angle X-ray scattering method is 0.5 to 5 nm.
The lithium secondary battery described. 4. The carbonaceous material further contains B.
4. Lithiu according to any one of claims 1 to 3, characterized in that
Rechargeable battery. 5. The non-aqueous electrolyte is propylene carbonate.
, Dimethyl carbonate, methyl ethyl carbonate
, Diethyl carbonate and γ-butyrolactone
At least one non-aqueous solvent selected from the group consisting of
A ranger and a bonnet are included.
4. The lithium secondary battery according to any one of 4 above. 6. The carbonaceous material is natural graphite or petroleum pit.
Selected from the group consisting of
Selected materials, isotropic pitch, polyacrylonitrile
Le, furfuryl alcohol, furan resin, phenol
From resin, cellulose, sugar and polyvinylidene chloride
A non-graphitizable carbon precursor selected from the group consisting of
The mixture was heat treated in the range of 800-3000 ° C.
The lithium secondary battery according to claim 1, wherein
pond. 7. The manufacture of the lithium secondary battery according to claim 1.
The carbonaceous material is natural graphite, petroleum pitch, mesophase.
A material selected from the group consisting of pitch and coke,
Isotropic pitch, polyacrylonitrile, full free lure
Rucor, furan resin, phenolic resin, cellulose
Selected from the group consisting of sugar, sugar and polyvinylidene chloride.
The mixture containing a non-graphitizable carbon precursor of 800 to
According to the method including the step of heat treatment in the range of 3000 ° C.
Manufacture of lithium secondary battery characterized by being manufactured by
Method.