JP3291755B2 - Non-aqueous solvent secondary battery and its electrode material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous solvent secondary battery (hereinafter simply referred to as a secondary battery), and more particularly to a secondary battery having a high capacity, excellent charge / discharge characteristics, a wide operating temperature range, and its electrode. About the material.

[0003]

2. Description of the Related Art Development of lithium secondary batteries has attracted attention as high capacity secondary batteries, and various materials have been studied as electrode materials. However, a substance satisfying both the electrode capacity and the charge / discharge characteristics has not been found. For example, a conductive polymer such as polyacetylene has a problem particularly in lithium ion doping ability and charge / discharge cycle stability.

When lithium metal is used for the negative electrode, the charge / discharge cycle characteristics are extremely poor for the following reasons. That is, when Li which has turned into ions from the negative electrode body and moved into the electrolytic solution at the time of discharging of the battery deposits on the negative electrode body at the time of charging, it becomes dendrite with repetition of the charge / discharge cycle. Since the dendritic Li has a very high activity, it decomposes the electrolytic solution and deteriorates the charge / discharge cycle characteristics of the battery. In addition, when the dendritic Li grows, it finally penetrates through the separator to reach the positive electrode body, causing a short circuit, so that the charge / discharge cycle life is short.

On the other hand, it has been proposed to use a carbonaceous material obtained by calcining an organic compound as a carrier and a material in which Li or an alkali metal mainly composed of Li is carried as the carrier as the negative electrode. In this configuration, since the lithium ions are included in the expansion of the aromatic ring network between the carbon crystals or in the amorphous portion, they do not become dendritic even when electrodeposited. As a result, the charge / discharge cycle characteristics of the negative electrode were dramatically improved, but no satisfactory electrode capacity was obtained.

An object of the present invention is to provide a combination of a negative electrode material having a large electrode capacity and excellent charge / discharge cycle characteristics and a specific electrolytic solution to provide a large capacity, excellent charge / discharge cycle characteristics, and a wide operating temperature range. An object of the present invention is to provide a secondary battery.

[0007]

Configuration of the Invention

[0008]

A non-aqueous solvent secondary battery according to the present invention comprises a rechargeable positive electrode, a rechargeable negative electrode, and a non-aqueous electrolyte obtained by dissolving an electrolyte salt. In a secondary battery, the negative electrode contains 50 carbonaceous materials satisfying the following (1):
A non-aqueous solvent secondary battery, wherein the wt% to 98 wt% containing over there.

(1) It has a multi-phase structure of at least two phases of a carbonaceous material forming a nucleus and a surface carbonaceous material formed on the surface of the nucleus, and the (002) plane spacing by X-ray wide-angle diffraction d ₀₀₂
Has a peak (P _A ) of 3.35 ° to 3.39 ° corresponding to the carbonaceous material forming the nucleus, and a peak (P _A ) corresponding to the surface carbonaceous material.
The corresponding peak between 3.45 ° and 3.75 ° (P
_B ) The ratio I _(3.45-3.75) / I of the integrated intensity of the diffraction curve having at least two peaks and having both peaks
_{(3.35 to 3.39)} is 0.10 or more and 1.60 or less, the volume average particle size is 2 μm or more and 70 μm or less, and the specific surface area measured by the BET method is 0.2 m ² / g or more and 5 m ² / g or less. Particles of carbonaceous material. Preferably, the carbonaceous material has an R value of 0.5 as determined by Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 °.
It is a non-aqueous solvent secondary battery characterized by having 4 or more. R = I _B / I _A (in the Raman spectrum, 15
Has a peak P _{A in} the range of 80 to 1620 cm ⁻¹ ,
Has a range to the peak P _B in 0～1370Cm ^-1, the intensity of the P _A I _A, and the intensity I _B of P _B) In addition, it further preferably electrolyte electrolytic solution satisfies the following (2) And a non-aqueous solvent secondary battery. (2) An electrolyte solution obtained by dissolving an alkali metal salt or a quaternary alkyl ammonium salt in a solvent containing propylene carbonate or butylene carbonate in an amount of 20 vol% or more and less than 100 vol%.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrode material of the present invention is a carbonaceous material having at least two phases of a carbonaceous material forming a nucleus and a surface carbonaceous material formed on the surface of the nucleus. This multiphase carbonaceous material has at least two diffraction peaks in wide-angle X-ray diffraction, corresponding to the multiphase structure. That is, the peak of X-ray wide-angle diffraction corresponding to the core carbonaceous material is 0
It has a peak in which the plane distance d ₀₀₂ of the 02 plane is 3.35 ° or more and 3.39 ° or less, preferably 3.36 ° or more and 3.38 ° or less, more preferably 3.36 ° or more and 3.37 ° or less.

The size (Lc) of the crystallite in the C-axis direction corresponding to this peak is preferably 200 ° or more, more preferably 220 ° or more, further preferably 300 ° or more, particularly preferably 600 ° or more, and most preferably 7 ° or more.
It is not less than 00 ° and not more than 1000 °. In addition, as a peak of X-ray wide-angle diffraction corresponding to the carbonaceous material in the surface layer, d ₀₀₂ is 3.
45 ° or more and 3.75 ° or less, more preferably 3.46 °
Not less than 3.70 °, more preferably not less than 3.47 ° and not more than 3.65 °, particularly preferably not less than 3.47 ° and not more than 3.47 °.
60 ° or less, most preferably 3.48 ° to 3.58 °
It has the following peaks:

Lc corresponding to this peak is preferably from 7 ° to less than 150 °, more preferably from 10 ° to 70 °, further preferably from 12 ° to 50 °,
It is particularly preferably at least 15 ° and at most 40 °, most preferably at least 17 ° and at most 35 °. Note that the peaks in the X-ray wide-angle diffraction pattern were obtained by approximating the profile of each peak with an asymmetric Pearson VII function and separating them by the least squares method using the Gauss-Jordan method.

Let I _(3.45 to _3.75, integrated intensity _{) be} the sum of the integrated intensities of the diffraction curves having a peak at ₀₀₂ from 3.45 ° to _3.75 °, and let I _(3.35 to _3.39 , integrated intensity ₎ be d.
_{If 002} is the sum of the integrated intensities of the diffraction curves having peaks at 3.35 to 3.39 °, the ratio I _(3.45 to _3.75 ,
₍ Integrated intensity ₎ / I _(3.35 to _3.39 , integrated intensity ₎ is preferably 0.10 or more and 1.60 or less, more preferably 0.15 or more and 1.50 or less, and even more preferably 0.20 or more and 1.4.
0 or less, particularly preferably 0.51 or more and 1.30 or less, and most preferably 0.90 or more and 1.20 or less.

[0014] Peak intensity ratio I of two separated peaks
_(3.45 to _3.75) / I _(3.35 to _3.39) is at least 0.01, preferably at least 0.012, more preferably at least 0.014, further preferably at least 0.020, particularly preferably at least 0.07, most preferably Preferably 0.10 or more and 0.35
It is as follows. Here, I _(3.45 to _3.75) is _d002 of 3.4.
Peak intensity of a peak of 5 ° or more and 3.75 ° or less;
For I _(3.35 to _3.39) , d ₀₀₂ is 3.35Å or more and 3.39Å
These are the peak intensities of the following peaks.

Further, the carbonaceous material serving as a nucleus further comprises two or more phases.
Consists of d in wide-angle X-ray diffraction.₀₀₂Is 3.35
It has two or more peaks in the region from Å to 3.39Å
You. Also, when the carbonaceous material as the surface layer is composed of two or more phases
Is d in wide-angle X-ray diffraction. ₀₀₂Is more than 3.45Å
The region has two or more peaks. In this case I_(3.45~
_3.75)As d₀₀₂Not less than 3.45 ° and not more than 3.75 °
Sum of peak intensities, I_(3.35~_3.39)As d
₀₀₂Is the peak of 3.35 ° or more and 3.39 ° or less
As the sum of the intensities, the intensity ratio of the two, I_(3.45~_3.75)/ I
_(3.35~_3.39)Is preferably in the above range of values
No.

Further, the electrode material of the present invention has a wavelength of 5145.
In the Raman spectrum analysis using the argon ion laser light of (4), it has the following spectral characteristics.
Hereinafter, spectra and peaks are Raman spectra under the same conditions unless otherwise specified. That is, when the R value represented by the formula (1) is 0.40 or more, preferably 0.1.
45 or more, more preferably 0.50 or more and 1.80 or less,
It is more preferably 0.55 or more and 1.50 or less, particularly preferably 0.60 or more and 1.30 or less, and most preferably 0.70 or more and 1.10.

R = I _B / I _A (1) where I _A is 1580 to
Intensity of peak P _A existing in the range of 1620 cm ⁻¹ , I _B
Is the peak P _B existing in the range of 1350 to 1370 cm ⁻¹
The strength of The fine structure of the carbonaceous material forming the surface layer contributes to the Raman spectrum.

That is, P _A is a peak observed corresponding to a crystal structure formed by growing and forming an aromatic ring network, and P _B is a peak corresponding to a disordered amorphous structure. . Both peak intensities I _B, the ratio of I _A R (= I _B /
I _A) shows carbonaceous material, i.e. a carbonaceous particle, a larger value as the ratio of the amorphous structure portion is greater in the surface layer, such as carbonaceous fibers.

The position of P _A changes depending on the degree of completeness of the crystal part. Position of P _A carbon material for use in the present invention is a 1580～1620Cm ^-1, as described above, preferably in the range of 1580～1610Cm ^-1, more preferably 1585~1600cm ^-1. The half width at half maximum of the peak is narrower as the higher order structure of the carbonaceous material is more uniform. Half width at half maximum of the P _A carbonaceous material are use in the present invention is preferably 8 cm ^-1 or more, more preferably 10 cm ^-1 or more, more preferably 12～60Cm ^-1, particularly preferably 13~55cm
^-1 , most preferably 15 to 50 cm ^-1 .

P _B usually has a peak at 1360 cm ^-1 . Half width at half maximum of the P _B is preferably 20 cm ^-1 or more, more preferably 20～150Cm ^-1, more preferably 25 to
125 cm ^-1, particularly preferably 28~110cm ^-1, most preferably 30~100cm ^-1. The electrode material of the present invention has a G value represented by the formula (2) of 0.40 or more, preferably 0.50 or more and 1.80 or less, more preferably 0.55 or more and 1.50 or less, and still more preferably. 0.60
Not less than 1.30 and particularly preferably not less than 0.65 and not more than 1.30.
20 or less, most preferably 0.70 or more and 1.10.

[0021]

(Equation 1)

The true density of the electrode material of the present invention is preferably from 2.00 g / cc to 2.20 g / cc, more preferably from 2.03 g / cc to 2.18 g / cc, and further preferably 2.05 g / cc. / Cc or more and 2.16 g / cc or less, particularly preferably 2.07 g / cc or more and 2.15 g / cc or less, and most preferably 2.09 g / cc or more and 2.14 g / cc or less. The true density of the carbonaceous material is given as an average true density of the entire carbonaceous material included in the multiphase structure including the surface layer and the core.

Also, in the differential thermal analysis, according to the above-mentioned multi-phase structure, at least two exothermic peaks overlap each other and exhibit an exothermic behavior in a wide temperature range. Preferably,
It shows an exothermic behavior in a temperature range of 100 ° C. or more, more preferably 150 ° C. or more, further preferably 200 ° C. or more, particularly preferably 250 ° C. or more and 500 ° C. or less, most preferably 280 ° C. or more and 400 ° C. or less.

The end temperature of the exothermic peak is preferably 80
0 ° C or higher, more preferably 810 ° C or higher, still more preferably 820 ° C or higher and 980 ° C or lower, particularly preferably 83 ° C or higher.
0 ° C to 970 ° C, most preferably 840 ° C to 9
50 ° C. or less. The starting end temperature of the exothermic peak is preferably 700 ° C. or lower, more preferably 680 ° C. or lower, further preferably 550 ° C. or higher and 680 ° C. or lower, particularly preferably 570 ° C. or higher and 670 ° C. or lower, and most preferably 580 ° C. or lower.
It is not less than 650 ° C and not less than 650 ° C.

The exothermic peak temperature is preferably 650.
C. to 840.degree. C., more preferably 660.degree.
5 ° C. or lower, more preferably 670 ° C. to 830 ° C., particularly preferably 680 ° C. to 820 ° C., and most preferably 690 ° C. to 810 ° C. Further, the electrode material of the present invention has a volume average particle diameter of preferably 6 μm or more and 80 μm or less, preferably 10 μm or more and 60 μm or less,
More preferably, 12 μm or more and 50 μm or less, further preferably 15 μm or more and 45 μm or less, particularly preferably 1 μm or more and 45 μm or less.
It is 7 μm or more and 40 μm or less, most preferably 20 μm or more and 35 μm or less.

The carbonaceous material used in the present invention is B
The specific surface area measured using the ET method is 0 . 2m2 / g or more 5
m @ 2 / g or less, good Mashiku is less 0.5 m @ 2 / g or more 4m2 / g.

(Synthesis of Electrode Material) As described above, the electrode material according to the present invention comprises a carbonaceous material (N) serving as a nucleus and a carbonaceous material (S) constituting a surface layer. The core carbonaceous material (N) has a true density of at least 2.15 g / cc, more preferably at least 2.16 g / cc and at most 2.26 g / cc, even more preferably at least 2.18 g / cc and 2.26 g / cc. Hereinafter, particularly preferably, 2.19 g / cc or more and 2.25 g / cc or more.
cc or less, most preferably 2.20 g / cc to 2.24 g
/ Cc or less.

The carbonaceous material (N) has a (002) plane spacing d ₀₀₂ of 3.35 ° or more and 3.3 or more in X-ray wide-angle diffraction.
9 ° or less, preferably 3.35 ° or more and 3.38 ° or less,
More preferably, it has a peak of not less than 3.35 ° and not more than 3.37 °, most preferably not less than 3.35 ° and not more than 3.36 °. The crystallite size (Lc) in the C-axis direction is preferably 200 ° or more, more preferably 300 ° or more, further preferably 600 ° or more, particularly preferably 750 or more.
Å or more, most preferably 800 to 1000 Å.

The carbonaceous material (N) is in the form of particles or fibers, preferably in the form of particles. In the case of particles, the volume average particle diameter is preferably 0.5 μm or more and 30 μm or less,
More preferably 0.6 μm or more and 24 μm or less, further preferably 0.7 μm or more and 20 μm or less, particularly preferably 0.7 μm or more and less than 15 μm, and most preferably 0.8 μm or less and less than 15 μm.
μm or more and less than 10 μm.

On the other hand, in the case of a fibrous form, the average diameter is 20 μm.
m or less, preferably 18 μm or less, more preferably 15 μm or less.
μm or less, more preferably 14 μm or less, particularly preferably 0.1 μm or more and 12 μm or less, and most preferably 0.2 μm or more and 10 μm or less. The specific surface area U (N) of the carbonaceous material (N) is preferably 300 m ² / g or less, more preferably 0.1 m ² / g or more and 200 m ² / g or less, and still more preferably 1 m ² / g or more and 100 m ² / g. Hereinafter, it is particularly preferably from 3 m ² / g to 50 m ² / g, most preferably from 5 m ² / g to 30 m ² / g.

The carbonaceous material (N) comprises (A) an organic compound,
300-3000 in a stream of inert gas or in vacuum
(B) a method of decomposing by heating at a temperature of 500 ° C., preferably 500 to 3000 ° C. to carry out carbonization and graphitization,
It can be obtained by a method in which carbonaceous materials such as carbon black and coke are further heated to appropriately promote carbonization, and a method in which (C) artificial graphite, natural graphite, and vapor-grown graphite whiskers are used as they are.

As the organic compound in the method (A),
Condensed polycyclic hydrocarbons obtained by condensing two or more monocyclic hydrocarbon compounds having three or more rings with each other, such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene, naphthacene, picene, perylene, pentaphen, and pentacene Compounds; or derivatives of the above compounds, such as carboxylic acids, carboxylic anhydrides, and carboxylic imides; various pitches whose main component is a mixture of the above compounds; indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole , At least two or more three-membered heterocyclic monocyclic compounds such as acridine, phenazine, and phenanthridine are bonded to each other, or are bonded to one or more three- or more-membered monocyclic hydrocarbon compounds. A carboxylic acid or carbohydrate of each of the above compounds Acid anhydrides, derivatives such as carboxylic acid imide; and benzene, toluene, aromatic monocyclic hydrocarbon, such as xylene, and their carboxylic acid,
Carboxylic anhydrides, derivatives such as carboxylic imides,
For example, derivatives such as 1,2,4,5-tetracarboxylic acid, its dianhydride and its diimide can be mentioned.

The above pitch will be described in more detail.
Examples include ethylene heavy-end pitch, crude oil pitch, coal pitch, asphalt cracked pitch, and pitch generated by thermally decomposing polyvinyl chloride and the like, which are generated when naphtha is decomposed. Further, these various pitches are further heated under an inert gas flow or the like, and the quinoline insoluble content is preferably 80% or more, more preferably 90% or more.
As described above, more preferably, the mesophase pitch can be used at 95% or more.

Further, aliphatic saturated or unsaturated hydrocarbons such as propane and propylene, polyvinyl chloride,
Organic polymers such as vinyl halide resins such as polyvinylidene chloride and chlorinated polyvinyl chloride, acrylic resins such as poly (α-halogenated acrylonitrile), and conjugated resins such as polyacetylene and polyphenylene vinylene can also be used. .

In order to form the carbonaceous material (S) in the surface layer on the carbonaceous material (N) thus synthesized, for example, (1) an organic compound is coated on the surface of the carbonaceous material (N) to be a nucleus. (2) a method of carbonizing an organic compound on the surface of the carbonaceous material (N) to form the carbonaceous material (S), and then forming the carbonaceous material (S) as it is; A method of forming particles of a carbonaceous material having a specific surface area (U) of １ ／ or less of the surface area U (N); (3) carbonizing an organic compound on the surface of the carbonaceous material (N) to convert the carbonaceous material (S) After formation, any of the methods of performing a pulverizing step can be used. In this case, in any of the methods, the specific surface area U of the multilayered carbonaceous material is set to not more than １ ／ of the specific surface area U (N) of the core carbonaceous material (N). That is, U (N) ≧ 2U, preferably U (N) ≧ 3U.

The method (1) can be further subdivided into the following three ways. (1-1) A relatively low molecular weight organic compound is dissolved in an organic solvent, and this is mixed with a carbonaceous substance (N). The organic solvent is evaporated by heating, and the surface of the carbonaceous material (N) is coated with the organic compound, followed by heating and carbonization. Then, it is heated and decomposed to form a carbonaceous material in the surface layer. Organic compounds include benzene, aromatic monocyclic hydrocarbons such as toluene, naphthalene, phenanthrene, anthracene, triphenylene,
Condensed polycyclic hydrocarbons such as pyrene, chrysene, naphthacene, picene, perylene, pentaphene, pentacene, carboxylic acids, carboxylic acid anhydrides, derivatives such as carboxylic imides, and three members such as indole, isoindole, and quinoline Derivatives such as carboxylic acids, carboxylic anhydrides, and carboxylic imides of a heterocyclic compound having two or more rings can be used.

(1-2) The surface of the carbonaceous material (N) is coated with an organic polymer compound, and then thermally decomposed in a solid phase to form a carbonaceous material. Examples of the organic polymer include cellulose; phenolic resin; acrylic resins such as polyacrylonitrile and poly (α-halogenated acrylonitrile); polyamideimide resin; polyamide resin;

(1-3) The surface of the carbonaceous material (N) is coated with a condensed polycyclic hydrocarbon, a heteropolycyclic compound or the like. Thereafter, heating is performed to form a carbonaceous material (S) in the surface layer in the liquid phase. As the condensed polycyclic hydrocarbon, it is preferable to use the above-mentioned pitch. In particular, in this method, it is preferable to promote carbonization via a liquid crystal state called a mesophase to form a carbonaceous material (S).

The thermal decomposition temperature for forming the surface layer is usually lower than the temperature for synthesizing the core carbonaceous material,
~ 2000 ° C is preferred. When the organic compound is coated on the surface of the carbonaceous material (N) serving as a nucleus, the organic compound is coated until the specific surface area of the specific surface area U (N) of the core carbonaceous material (N) becomes 以下 or less. It is preferable to carbonize. It is more preferably 1/3 or less, further preferably 1/4 or less, particularly preferably 1/5 or less, and most preferably 1/6 or less.

In the synthesis of the core carbonaceous material (N),
By synthesizing the inner core, and then synthesizing the outer core, it is possible to synthesize a carbonaceous material that becomes a multiphase nucleus in multiple steps. Similarly, in the synthesis of the carbonaceous material to be the surface layer, the inner surface layer is synthesized, and the outer surface layer is synthesized thereon, whereby the carbonaceous material to be the multiphase surface layer can be synthesized in multiple steps. In the thus obtained carbonaceous material having a multiphase structure, the ratio of the core portion to the surface layer portion is preferably such that the core portion is 20% by weight or more and 70% by weight or less, more preferably 25% by weight or more and 65% by weight or less. It is preferably 30% by weight or more and 60% by weight or less, particularly preferably 35% by weight or more and 55% by weight or less, and most preferably 4% by weight or less.
0 to 50% by weight.

The surface layer preferably has a content of 30% by weight to 80% by weight, more preferably 35% by weight to 75% by weight, further preferably 40% by weight to 70% by weight.
The content is particularly preferably 45% by weight to 65% by weight, and most preferably 50% by weight to 60% by weight. The thickness of the surface layer surrounding the nucleus is preferably 100 to
5 μm, more preferably 200 to 4 μm, further preferably 300 to 3 μm, particularly preferably 500 to
2 μm, most preferably 700 ° -1.5 μm.

(Structure of Secondary Battery) Next, an embodiment of a secondary battery using the electrode material of the present invention will be described. The rechargeable battery is
It has a rechargeable positive electrode and a rechargeable negative electrode, and a separator that holds the electrolyte is interposed between the two.

(Formation of Negative Electrode) The negative electrode may be formed of only the electrode material of the present invention, or may be formed of a mixture of the electrode material and a metal which can be alloyed with an alkali metal or an alloy of an alkali metal. Can also.

Examples of the metal that can be alloyed with an alkali metal, preferably a metal that can be alloyed with a lithium metal include aluminum (Al), lead (Pb), zinc (Zn), tin (Sn), bismuth (Bi), and indium. (In), magnesium (Mg), gallium (Ga), cadmium (Cd), silver (Ag), silicon (Si), boron (B), antimony (Sb), and the like, and preferably Al, Pb, and In. , Bi and Cd, more preferably Al, Pb, In, and particularly preferably A
1, Pb, and most preferably Al.

As an alkali metal alloy, preferably a lithium metal alloy, the composition (molar composition) of the alloy is Li _x
M (x is a molar ratio to metal M), M
The above-mentioned metal is used as the metal. X is 0 <x ≦
9, preferably 0.1 ≦ x
≦ 5, more preferably 0.5 ≦ x ≦ 3,
Particularly preferably, 0.7 ≦ x ≦ 2.

The alloy may further contain other elements in the range of 50 mol% or less in addition to the above-mentioned metals. Further, two or more kinds of the above-mentioned alkali metal alloys can be used. The metal which can be alloyed with the alkali metal or the alloy of the alkali metal is preferably 3% by weight or more and 60% by weight or less, more preferably 5% by weight or less, in the mixture with the carbonaceous material of the present invention.
% By weight to 50% by weight, more preferably 7% by weight
The content is not less than 45% by weight, particularly preferably not less than 10% by weight and not more than 40% by weight, most preferably not less than 12% by weight and not more than 35% by weight. The most preferred form of the mixture is a form in which a carbonaceous material contains a metal or an alloy of an alkali metal that can be alloyed with an alkali metal and a carbonaceous material (N).

(Formation of Positive Electrode) The material of the positive electrode body is not particularly limited, but is preferably made of, for example, a metal chalcogen compound which releases or acquires an alkali metal cation such as Li ion along with a charge / discharge reaction. Such metal chalcogen compounds include vanadium oxides, vanadium sulfides, molybdenum oxides, molybdenum sulfides, manganese oxides, chromium oxides, titanium oxides, titanium sulfides and the like. And complex sulfides. Preferably Cr
₃ O ₈ , V ₂ O ₅ , V ₆ O ₁₃ , VO ₂ , Cr ₂ O ₅ , M
nO ₂ , TiO ₂ , MoV ₂ O ₈ ; TiO ₂ , V
₂ S ₅ , MoS ₂ , MoS ₃ , VS ₂ , Cr _0.25 V _0.75
And the like _{S 2, Cr 0. 5 V 0.5} S 2. Also, LiCo
Oxides such as O ₂ and WO ₃ ; CuS, Fe _0.25 V _0.75 S
_2, sulfides such as _{Na 0.1 CrS 2; NiPS 3,} Fe
Phosphorus, such as PS _3, sulfur compounds; VSe _2, NbSe
A selenium compound such as ₃ can also be used.

Further, conductive polymers such as polyaniline and polypyrrole, and specific surface areas of 10 m ² / g or more, preferably 100 m ² / g or more, more preferably 500 m ² / g
As described above, a carbonaceous material of at least 1000 m ² / g, most preferably at least 2000 m ² / g can be used for the positive electrode.

(Preparation of Electrolyte Solution) As the separator for holding the electrolyte solution, generally, a material having excellent liquid retention properties, for example, a nonwoven fabric of polyolefin such as polyethylene and polypropylene can be used.

The electrolytic solution is propylene carbonate or butylene carbonate in an amount of 20 vol% or more and 100 vol.
% Or less in a solvent containing LiClO ₄ , LiPF ₆ , L
iAsF ₆ , LiBF ₄ , LiSO ₃ CF ₃ , LiN
It is formed by dissolving an alkali metal salt such as (SO ₂ CF ₃ ) ₂ , a tetraalkylammonium salt and the like. As the solvent, propylene carbonate or butylene carbonate is preferably 25 vol% or more and 80 vol% or less, more preferably 30 vol% or more and 70 vol% or less, still more preferably 35 vol% or more and 65 vol% or less, particularly preferably 40 vol% or more and 60 vol% or less, and most preferably. Contains 45 vol% or more and 50 vol% or less.

As a mixed solvent other than propylene carbonate or butylene carbonate, a cyclic ester compound such as ethylene carbonate is preferably used in an amount of 1 vol% to 50 vol%, more preferably 2 vol% to 40 vol%, and still more preferably. Contains 5 vol% or more and 35 vol% or less, particularly preferably 10 vol% or more and 30 vol% or less, and most preferably 15 vol% or more and 25 vol% or less.

In particular, ethylene carbonate is preferably used in an amount of 2 to 60 parts by volume, more preferably 5 to 50 parts by volume, based on 100 parts by volume of a mixed solvent of propylene carbonate and ethylene carbonate.
More preferably, the mixed solvent contains 10 to 40 parts by volume, particularly preferably 12 to 30 parts by volume, and most preferably 15 to 25 parts by volume.

Further, 1,2-dimethoxyethane, crown ether (12-crown-4, etc.),
It may contain ether compounds such as dioxolane and tetrahydrofuran or chain ester compounds such as diethyl carbonate. In this case, the ether compound or the chain ester compound in the mixed solvent is preferably 1
0 vol% or more and 85 vol% or less, more preferably 15 vol% or less.
vol% to 80 vol%, more preferably 18 vol% or less.
vol% or more and 70 vol% or less, particularly preferably 20 vol% or less.
vol% or more and 60 vol% or less, most preferably 30 v
ol% or more and 50 vol% or less.

In a secondary battery constructed as described above, for example, a secondary battery using a metal chalcogen compound for the positive electrode and the carbonaceous material of the present invention for the negative electrode, the active material ions (especially, (Preferably lithium ions), and the active material ions are released at the time of discharge, whereby the charge / discharge electrode reaction proceeds. In the positive electrode, active material ions are released from the positive electrode body during charging,
During discharge, active material ions are doped, and the electrode reaction of charge and discharge proceeds.

In a secondary battery in which the above-mentioned conductive polymer or a carbonaceous material having a large specific surface area is used for the positive electrode and the carbonaceous material of the present invention is used for the negative electrode, the cation in the electrolyte is charged at the time of charging at the negative electrode. At the time of discharge, cations in the negative electrode body are released, and the electrode reaction of charge and discharge proceeds. On the other hand, in the positive electrode, the anion in the electrolytic solution is doped at the time of charging, and at the time of discharging, the anion in the positive electrode body is released, and the electrode reaction of charge and discharge proceeds.

A secondary battery using the carbonaceous material of the present invention for a negative electrode exhibits excellent balance between secondary battery capacity and long-term charge / discharge cycle characteristics and excellent safety. In addition, in this invention, each measurement of X-ray wide-angle diffraction, density, etc. was implemented by the following method.

X-ray Wide Angle Diffraction (1) Spacing (d) of (002) plane₀₀₂) And (110)
Surface spacing (d₁₁₀) If the carbonaceous material is powder, leave it as it is
Powdered in an agate mortar, about 15% by weight based on carbonaceous matter
High purity silicon powder for X-ray standard as internal standard material
Mix and pack into sample cell. Graphite monochrome
The source is CuKα radiation monochromated by a
Measure wide-angle X-ray diffraction curve by lacometer method
You. To correct the curve, the so-called Lorentz, polarization factor,
No correction is made for absorption factors, atomic scattering factors, etc.
Use the simple method. That is, (002) and (110) diffraction
Draw the baseline of the curve corresponding to
The real intensity is plotted again to obtain a (002) plane, and
A correction curve for the (110) plane is obtained. The peak height of this curve
The line parallel to the angle axis drawn at two-thirds of the height is the diffraction curve
The midpoint of the line segment that intersects
Correcting this to twice the diffraction angle, the wavelength λ of the CuKα ray and
From equation (3), d is given by the Bragg equation.₀₀₂And d ₁₁₀To
Ask.

[0058]

(Equation 2) λ: 1.5418 ° θ, θ ′: diffraction angle corresponding to d ₀₀₂ , d ₁₁₀ (2) Size of crystallite in c-axis and a-axis directions: Lc; La In the corrected diffraction curve obtained in the preceding section, The size of crystallites in the c-axis and a-axis directions is obtained from the following equation using the so-called half width β at half the peak height.

[0059]

(Equation 3) 0.90 was used as the shape factor K. λ, θ and θ ′ have the same meaning as in the previous section.

The measurement was carried out using a multipycnometer manufactured by Yuasa Ionics Inc. using a gas replacement method with helium gas.

Example 1 (1) Formation of Negative Electrode In X-ray wide-angle diffraction, the true density was 2.23 g / cc, d
₀₀₂ is 3.37 °, average particle size is 2 μm, specific surface area is 20 m ²
/ G of the carbonaceous material was heated with stirring in a solution of pitch (a mixture of condensed polycyclic hydrocarbon compounds) in a toluene solvent to coat the pitch on the surfaces of the particles of the carbonaceous material.

Then, the temperature was raised to 1300 ° C. at a rate of 20 ° C./min under a nitrogen flow, and carbonized at 1300 ° C. for 30 minutes to form carbonaceous material particles having a multi-phase structure. Thus, particles having an average particle size of 24 μm were obtained. As a result of the measurement, the ratio of the carbonaceous material in the surface layer was 100 parts by weight with respect to 100 parts by weight of the core carbonaceous material. The R was 0.74 in Raman spectrum analysis using argon ion laser light (5145 °).

The true density was 2.10 g / cc, and the BET specific surface area was 3.8 m ² / g. D ₀₀₂ in X-ray wide angle diffraction
Has two peaks at 3.37 ° and 3.51 °, and the integrated intensity ratio of the diffraction curve having both peaks (I _3.51 Å / I
_3.37Å ) was 0.95. 6 parts by weight of polyethylene was mixed with 94 parts by weight of the carbonaceous material, and the mixture was compression-molded into a pellet having a diameter of 16 mm. This was heated to 130 ° C. in a vacuum and dried to form a negative electrode.

(2) Formation of Positive Electrode After 500 mg of V ₂ O ₅ -P ₂ O ₅ , 25 mg of polytetrafluoroethylene and 25 mg of carbon black were kneaded to form a sheet, a pellet electrode having a diameter of 16 mm was formed.

(3) Formation of Secondary Battery Cell and Evaluation of Secondary Battery Performance Prior to assembling the secondary battery cell, a positive electrode was prepared by using lithium metal as a counter electrode in a propylene carbonate solution containing 1.0 mol / liter LiClO _4. 1.2 electrodes
The battery was precharged at 15 mA for 15 hours. Similarly, the negative electrode was precharged at 1.2 mA for 7 hours.

Then, LiClO ₄ was converted to propylene carbonate (75 vol%) and ethylene carbonate (25 vol.
vol%) of a mixed solvent of 1 mol / liter in a mixed solvent was impregnated with a polypropylene separator impregnated between the two electrodes to form a secondary battery cell. This secondary battery cell was placed in a thermostat at 20 ° C., and the operation of charging the battery between both electrodes to 3.3 V with a constant current of 1 mA and discharging the battery to 1.8 V was repeated. Table 1 shows the characteristics at the 5th cycle and the 15th cycle.

Comparative Example 1 (1) Formation of Negative Electrode The carbonaceous material used as a nucleus in Example 1 was used as a negative electrode material without forming a carbonaceous material on the surface layer. The carbonaceous material is d ₀₀₂ 3.37 Å, an R value of 0.10 in the Raman spectrum separation and an average particle diameter of a particle of 2 [mu] m. The formation of the negative electrode was performed in the same manner as in Example 1.

(2) Formation of Positive Electrode A positive electrode was formed in the same manner as in Example 1. (3) Configuration and Evaluation of Secondary Battery Cell A secondary battery cell was configured in the same manner as in Example 1, and its secondary battery characteristics were evaluated.

Comparative Example 2 (1) Preparation of Negative Electrode The pitch was set in an electric heating furnace, and the pitch was set to 20 under a nitrogen flow.
After holding at 1300 ° C for 30 minutes at a heating rate of ° C / min,
It was pulverized into particles having an average particle size of 24 μm. The carbonaceous material, d ₀₀₂ in the X-ray wide angle diffraction had only peaks of 3.48A. Using this carbonaceous material, a negative electrode was formed in the same manner as in Example 1.

(2) Preparation of Positive Electrode A positive electrode was prepared in the same manner as in Example 1. (3) Configuration and Evaluation of Battery Cell A battery cell was configured in the same manner as in Example 1, and its secondary battery characteristics were evaluated and summarized in Table 1.

[0071]

[Table 1]

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/02 H01M 4/58 H01M 10/40

Claims (3)

(57) [Claims] 1. A secondary battery comprising a rechargeable positive electrode, a rechargeable negative electrode, and a non-aqueous electrolyte obtained by dissolving an electrolyte salt, wherein the negative electrode satisfies the following (1): A non-aqueous solvent secondary battery comprising 50% by weight to 98% by weight of a carbonaceous material. (1) It has a multiphase structure of at least two phases of a carbonaceous material forming a nucleus and a surface carbonaceous material formed on the surface of the nucleus, and the (002) plane spacing d _{002 obtained} by X-ray wide-angle diffraction is _large. 3.3 corresponding to the carbonaceous material forming the nucleus
The peak (P _A ) between 5 ° and 3.39 ° and the surface coal
It has at least two peaks (P _B ) from _{3.45 °} to 3.75 ° corresponding to the substance, and the ratio I _{(3.45 to 3.75)} of the integrated intensity of the diffraction curve having both peaks.
/ I _{(3.35 to 3.39)} is 0.10 or more and 1.60 or less, the volume average particle size is 2 μm or more and 70 μm or less, and B
Specific surface area measured by ET method is 0.2 m ² / g or more and 5 m ²
/ g particles of carbonaceous material. 2. The carbonaceous material according to claim 1, wherein, in a Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 °, the R value represented by the following formula is 0.4 or more. Water solvent secondary battery. R = I _B /
I _A (1580 to 1620 in Raman spectrum
with a peak P _{A in} the range of cm ⁻¹ , 1350-1370 cm
Range of ^-1 to a peak P _B, the strength of P _A I _A, and the intensity I _B of P _B) 3. The non-aqueous solvent secondary battery according to claim 1, wherein the electrolyte is an electrolyte satisfying the following (2). (2) 20v of propylene carbonate or butylene carbonate
An electrolyte solution obtained by dissolving an alkali metal salt or a quaternary alkyl ammonium salt in a solvent containing at least 100% by volume and less than 100% by volume.