JPH05335016A - Non-aqueous solvent secondary battery and its electrode material - Google Patents

Abstract

PURPOSE:To enlarge the capacity, enhance the charge/discharge cyclic characteristics, and enhance the reliability by introducing a combination of a specific electrolyte with a negative electrode material which includes a specified quantity of carbonaceous substance particles of multi-layer structure. CONSTITUTION:As an electrode material is used a carbonaceous substance of a multi-phase structure, at least two phases, consisting of a carbonaceous substance (N) forming a nucleus and another (S) at the facial layer formed over the surface of this nucleus. Particles of this substance has a peak with the (200) plane spacing d002 due to X-ray wide angle diffraction as ranging between 3.35-3.37Angstrom and an R value due to Raman spectral analysis using a 5145-Angstrom argon ion laser as ranging 0.11-1.0, and further the specific surface area (Sm<2>/g) and true density (rhog/cm<3>) are related to meet S<=41-15rho. The electrolyte used is prepared by dissolving alkali metal salt, etc., in a hybrid solvent containing 5-60vol.% ethylene carbonate and 3-85vol.% ring-shaped ether compound etc.

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 particularly to a secondary battery having high capacity, excellent charge / discharge characteristics, and high reliability, and an electrode material for the secondary battery. Regarding

[0003]

2. Description of the Related Art Development of a lithium secondary battery as a high-capacity secondary battery is drawing attention, and various substances have been studied as electrode materials. However, no substance has been found that satisfies both the electrode capacity and the charge / discharge characteristics. For example, conductive polymers such as polyacetylene have problems 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 become ions from the negative electrode body during the discharge of the battery and has moved into the electrolytic solution, is electrodeposited on the negative electrode body during the charge, it becomes dendrite-like as the charge / discharge cycle is repeated. Since dendrite Li is extremely highly active, it decomposes the electrolytic solution and deteriorates the charge / discharge cycle characteristics of the battery. In addition, when the dendrite-like Li grows, it finally penetrates the separator and reaches the positive electrode body to cause a short circuit, so that the charge / discharge cycle life is short.

On the other hand, it has also been proposed to use a carbonaceous material obtained by firing an organic compound as a carrier, and a substance in which Li or an alkali metal mainly composed of Li is supported as a negative electrode. In this structure, since lithium ions are included in the inter-layer of the carbon crystals or the spread of the aromatic ring network in the amorphous part, even if lithium is electrodeposited, it does not form a dendrite form. Therefore, the charge / discharge cycle characteristics of the negative electrode have been dramatically improved, but a satisfactory electrode capacity has not been obtained.

An object of the present invention is to provide a negative electrode material having a large electrode capacity and excellent charge / discharge cycle characteristics. Another object of the present invention is to provide a secondary battery having a large capacity, excellent charge / discharge cycle characteristics, and high reliability by combining the negative electrode material with a specific electrolytic solution.

[0007]

[Constitution of the invention]

[0008]

The electrode material of the present invention is carbonaceous material particles having a multiphase structure, and the carbonaceous material particles have a surface spacing d ₀₀₂ of (002) plane of 3 by X-ray wide angle diffraction. It has a peak of 0.35Å or more and 3.37Å or less, and a wavelength of 5
In a Raman spectrum analysis using a 145Å argon ion laser beam, the following R value is 0.11 or more and 1.0 or more.
Below, the specific surface area (Sm ² / g) and true density (ρg / cm)
³ ) is a carbonaceous material satisfying S ≦ 41−15ρ. R = I _B / I _A (in the Raman spectra, 1580
Having a peak P _{A in} the range of ˜1620 cm ⁻¹ ,
It has a peak P _{B in} the range of 1370 cm ^-1 , and the intensity of P _A is I _A and the intensity of P _B is I _B )

The secondary battery according to the present invention is a secondary battery having a rechargeable positive electrode, a rechargeable negative electrode, and a non-aqueous electrolyte solution in which an electrolyte salt is dissolved. Contains 50 to 98% by weight of the above carbonaceous material, and the electrolytic solution is an electrolytic solution satisfying the following (2). (2) 60v of ethylene carbonate 5vol% or more
An electrolytic solution obtained by dissolving an alkali metal salt or a quaternary alkylammonium salt in a mixed solvent containing less than 1% by weight and a cyclic ether or chain ester compound in an amount of 3% by volume or more and 85% or less.

[0010]

EXAMPLE The electrode material of the present invention is a carbonaceous material having a multi-phase structure of at least two phases, that is, a carbonaceous material (N) forming a nucleus and a carbonaceous material (S) formed on the surface of the nucleus. is there. This multiphase carbonaceous material has at least two diffraction peaks in X-ray wide angle diffraction, corresponding to the multiphase structure. That is, as the peak of the X-ray wide-angle diffraction corresponding to the carbonaceous material (N) of the nucleus, the interplanar spacing d ₀₀₂ of the 002 plane is 3.3.
5Å or more and 3.37Å or less, preferably 3.35Å or more and 3.37Å or less, more preferably 3.35Å or more and 3.3.
It has a peak of 6 Å or less. The size (Lc) of the crystallite in the C-axis direction corresponding to this peak is preferably 200 Å or more, more preferably 300 Å or more, further preferably 600 Å or more, particularly preferably 750 Å or more, most preferably 800 Å or more and 1000 Å or less. Is.

X corresponding to the carbonaceous material (S) on the surface layer
2. As the peak of wide-angle diffraction, d ₀₀₂ is 3.38 Å or more.
75Å or less, more preferably 3.39Å or more and 3.70Å
Or less, more preferably 3.40 Å or more and 3.65 Å or less, particularly preferably 3.41 Å or more and 3.60 Å or less,
Most preferably, it has a peak of 3.45Å or more and 3.60Å or less. Further, Lc corresponding to this peak is preferably 300 Å or less, more preferably 250 Å or less, further preferably 12 Å or more and 220 Å or less, particularly preferably 15 Å or more and less than 200 Å, most preferably 17 Å or more and 150 Å or less.

The peaks in the X-ray wide-angle diffraction pattern were separated by the least squares method applying the Gauss-Jordan method by approximating the profile of each peak by the asymmetric Pearson VII function. Peak intensity ratio I of two separated peaks
_(3.43 ~ ₎ / I _(3.35 ~ _3.39) is 0.002 or more, preferably 0.005 or more and 0.080 or less, more preferably 0.008 or more and 0.050 or less, and still more preferably 0.00.
010 or more and less than 0.030, particularly preferably 0.01
It is 5 or more and 0.029 or less. Where I _(3.43 ~ ₎ is d
₀₀₂ is the peak intensity of the peak of 3.43Å or more, and I
_(3.35 to _3.39) is the peak intensity of the peak in which d ₀₀₂ is 3.35Å or more and 3.39Å or less.

Further, the ratio of the diffraction intensity I ₍₂ θ _{= 25} ° ₎ at 2θ (diffraction angle) = 25.0 ° to I _(3.35 to _3.38) I ₍₂ θ _{= 25} ° ₎ / I _(3.35 to _3.38) is preferably 0.
002 or more and 0.080 or less, more preferably 0.005
Or more and 0.050 or less, more preferably 0.008 or more and less than 0.030, particularly preferably 0.010 or more and 0.0
29 or less, most preferably 0.012 or more and less than 0.028.

Further, the carbonaceous material (N) as the core is further 2
When it consists of two or more phases, it has two or more peaks in the region where d ₀₀₂ is 3.35 Å or more and less than 3.37 Å in X-ray wide angle diffraction. Similarly, when the surface carbonaceous material further comprises two or more phases, d ₀₀₂ is 3. in X-ray wide angle diffraction.
It has two or more peaks in the region of 38 Å or more. In this case d ₀₀₂ is sum ΣI _{(3.38 ~)} of the peak intensity of a peak of more than 3.38 Å, the sum of the peak intensity of the peak d ₀₀₂ is less than than 3.35 Å 3.37 Å and ΣI _{(3.3 5} ~ _3.37) Then, the intensity ratio ΣI _(3.38 ~ ₎ / ΣI _(3.35 ~
_3.37) is preferably in the same range of values as in the case of the above-mentioned single layer structure.

Further, I _{(3.38- ,} integrated intensity ₎ is d ₀₀₂
Is the sum of integrated intensities of peaks above 3.38Å, I _(3.35
〜 _3.37 , integrated intensity ₎ d ₀₀₂ is 3.35 Å or more 3.37
Å If the sum of the integrated intensities of the peaks below is
_(3.38 ~, integrated intensity ₎ / I _{( 3.35} ~ _3.37 , integrated intensity ₎ is preferably 0.001 or more and 0.80 or less, more preferably 0.002 or more and 0.60 or less, still more preferably 0.00.
003 or more and 0.50 or less, particularly preferably 0.004 or more and 0.40 or less, and most preferably 0.005 or more and 0.3
It is 0 or less.

Further, the electrode material of the present invention has a wavelength of 5145.
In Raman spectrum analysis using Å argon ion laser beam, it has the following spectral characteristics.
Hereinafter, unless otherwise specified, spectra and peaks are Raman spectra under the same conditions.

That is, the R value expressed by the equation (1) is 0.
11 or more and 1.0 or less, preferably 0.15 or more and 0.90
Or less, more preferably 0.20 or more and 0.80 or less, further preferably 0.30 or more and 0.75 or less, particularly preferably 0.35 or more and 0.70 or less, and most preferably 0.4.
It is 0 or more and 0.60 or less. _{R = I B / I A (} 1) except, I _A in Raman spectrum, 1580～
Intensity of peak P _A existing in the range of 1620 cm ⁻¹ , I _B
Is a peak P _B existing in the range of 1350 to 1370 cm ⁻¹
Is the strength of.

The fine structure of the carbonaceous material (S) forming the surface layer contributes to the Raman spectrum. That is, P _A is a peak observed corresponding to the crystal structure in which the spread of the aromatic ring network plane is stacked and grown, and P _B is a peak corresponding to the disordered amorphous structure. The ratio R (= I _B / I _A ) of the peak intensities I _B and I _A of the both shows a larger value as the ratio of the amorphous structure portion in the surface layer of the carbonaceous material, that is, the carbonaceous particles, the carbonaceous fiber, etc., increases. ..

Further, the position of P _A changes depending on the degree of perfection 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 1590~1600cm ^-1.

The full width at half maximum of the peak becomes narrower as the higher-order structure of the carbonaceous material becomes more uniform. P _A for carbonaceous material used in the present invention
The half-value half-width, preferably 8 cm ^-1 or more 55cm ^-1 or less, more preferably 10 cm ^-1 or more 50cm or less, more preferably 11～40Cm ^-1, particularly preferably 12~30cm ^-1. P _B usually has a peak at 1360 cm ^-1 . P
The half width at half maximum of _B is preferably 20 cm ⁻¹ or more, more preferably 20 to 120 cm ⁻¹ , further preferably 25 to 110.
cm ^-1, particularly preferably 30~100cm ^-1, most preferably 30~90cm ^-1.

The electrode material of the present invention has a G value represented by the formula (2) of 0.11 or more, preferably 0.20 or more and 1.50 or less, more preferably 0.25 or more and 1.30 or less, It is more preferably 0.30 or more and 1.10 or less, particularly preferably 0.35 or more and 0.80 or less, and most preferably 0.40 or more and 0.60 or less.

[0022]

[Equation 1]

The true density of the electrode material of the present invention is 2.05 g /
cc or more, preferably 2.08 g / cc or more, more preferably 2.10 g / cc or more and 2.20 g / cc or less, further preferably 2.12 g / cc or more and 2.20 g / cc or less, particularly preferably 2. 13 g / cc or more and 2.19 g / cc or less,
Most preferably, it is 2.14 g / cc or more and 2.18 g / cc or less. The true density of the carbonaceous material is given as the average true density of the entire carbonaceous material contained in the multiphase structure including the surface layer and the nucleus.

The electrode material of the present invention has a specific surface area S
(M ² / g) and true density (ρ / cm ³ ) are S ≦ 41−15
satisfies ρ. Preferably S ≦ 40−15ρ, more preferably S ≦ 39−15ρ, further preferably S ≦ 38-1.
5ρ, particularly preferably S ≦ 36−15ρ, most preferably S ≦ 38−15ρ.

The electrode material of the present invention has a volume average particle size of preferably 2 μm or more and 80 μm or less, preferably 4 μm.
m or more and 60 μm or less, more preferably 5 μm or more and 50 μm
m or less, more preferably 6 μm or more and 40 μm or less, and particularly preferably 7 μm or more and 35 μm or less.

Further, the carbonaceous material used in the present invention is
In analysis such as ESCA, the oxygen / carbon atom ratio on the surface is preferably 0.25 or less, more preferably 0.20 or less, further preferably 0.15 or less, particularly preferably 0.10 or less, most preferably 0. It is 07 or less.

Also in the differential thermal analysis, the exothermic behavior in a wide temperature range in which at least two exothermic peaks are overlapped is shown depending on the above-mentioned multiphase structure. Preferably,
Exothermic behavior is exhibited in a temperature range of 100 ° C. or higher, more preferably 150 ° C. or higher, further preferably 200 ° C. or higher, particularly preferably 250 ° C. or higher and 500 ° C. or lower, and most preferably 280 ° C. or higher and 400 ° C. or lower.

The end temperature of the exothermic peak is preferably 80.
0 ° C or higher, more preferably 810 ° C or higher, even more preferably 820 ° C or higher and 980 ° C or lower, and particularly preferably 83.
0 ° C to 970 ° C, most preferably 840 ° C to 9
It is 50 ° C or lower. The 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.
The temperature is not lower than 650 ° C and not higher than 650 ° C.

The exothermic peak temperature is preferably 650.
℃ or more and 840 ℃ or less, more preferably 660 ℃ or more 83
The temperature is 5 ° C or lower, more preferably 670 ° C or higher and 830 ° C or lower, particularly preferably 680 ° C or higher and 820 ° C or lower, and most preferably 690 ° C or higher and 810 ° C or lower.

Further, the carbonaceous material preferably has pores inside. The total pore volume and the average pore radius described below are determined by measuring the adsorbed gas amount (or desorbed gas amount) to the sample under several equilibrium pressures using a constant volume method,
It is determined by measuring the amount of gas adsorbed on the sample. The total pore volume is determined from the total amount of gas adsorbed at relative pressure P / P _O = 0.995, assuming that the pores are filled with liquid nitrogen. P: Adsorption gas vapor pressure (mmHg) P _O : Saturation vapor pressure of adsorption gas at cooling temperature (mmHg)

Adsorbed nitrogen gas amount (V_ads) From the following
Amount of liquid nitrogen filled in the pores using the formula (A)
(V_liq), The total pore volume is obtained. V_liq= (P_atm・ V_ads・ V_m) / RT (A) where P_atmAnd T are atmospheric pressure (Kgf / cm)²)
And absolute temperature (K), and R is a gas constant. V_mIs
Molecular volume of adsorbed gas (34.7 cm for nitrogen) ³/ Mol
 ) Is.

The carbonaceous material used in the present invention preferably has a total pore volume determined as described above of 1.5 × 10 ⁻³ ml /
g or more, more preferably 1.6 × 10 ⁻³ ml / g or more, 1
0 × 10 ⁻² ml / g or less, more preferably 1.7 × 10
^-3 or more and 9 × 10 ^-2 ml / g or less, particularly preferably 1.8
It is not less than ^{x10 -3 and not} more than ^{9x10 -2} ml / g, most preferably not less than 1.9x10 ^{-3 and not} more than ^{7x10 -2} ml / g. In particular, it is preferable to have the above total pore volume in the range where the pore radius is in the range of 10Å to 300Å.

The average pore radius (γ _p ) is calculated by using the following formula (B) from V _liq obtained from the above formula (A) and the specific surface area S obtained by the BET method. .. Here, it is assumed that the pores have a cylindrical shape. γ _p = 2V _liq / S (B) In this way, the average pore radius (γ _p ) of the carbonaceous material obtained from the adsorption of nitrogen gas is preferably 8 to 100Å. It is more preferably 10 to 80Å, further preferably 12 to 60Å, and particularly preferably 14 to 40Å.

Further, the carbonaceous material used in the present invention is
The pore volume measured by the mercury porosimeter is preferably 0.
02 ml / g or more and 5 ml / g or less, more preferably 0.03
ml / g or more and 4 ml / g or less, more preferably 0.04 ml
/ G or more and 3 ml / g or less, particularly preferably 0.05 ml /
It is not less than g and not more than 2 ml / g, most preferably not less than 0.06 ml / g and not more than 1.8 ml / g.

(Synthesis of Electrode Material) As described above, the electrode material according to the present invention is composed of the carbonaceous material (N) serving as the core and the carbonaceous material (S) constituting the surface layer.

The carbonaceous material (N) is in the form of particles or fibers, preferably particles. In the case of particles, the volume average particle size thereof is preferably 2 μm or more and 30 μm or less, more preferably 5 μm or more and 24 μm or less, further preferably 6 μm or more and 22 μm or less, particularly preferably 8 μm or more and less than 20 μm, and most preferably 10 μm or more and 18 μm or less. is there.

On the other hand, in the case of fiber, the average diameter is 20 μm.
m or less, preferably 18 μm or less, more preferably 15
It is not more than μm, more preferably not more than 14 μm, particularly preferably not less than 0.1 μm and not more than 12 μm, most preferably not less than 0.2 μm and not more than 10 μm. The specific surface area U (N) of the carbonaceous material (N) is preferably 70 m ² / g or less, more preferably 50 m ² / g or less, further preferably 0.1 m ²
/ G or more 30 m ² / g or less, particularly preferably 1.0 m ² /
It is not less than g and not more than 20 m ² / g, most preferably not less than 1.2 m ² / g and not more than 15 m ² / g.

The carbonaceous material (N) is the organic compound (A)
300 to 3000 in an inert gas flow or in a vacuum
(B) a method of decomposing by heating at a temperature of 50 ° C., preferably 500 to 3000 ° C. for carbonization and graphitization.
It can be obtained by a method of further heating a carbonaceous material such as carbon black or coke to appropriately advance carbonization, or a method of directly using (C) artificial graphite, natural graphite or vapor-grown graphite whiskers.

As the organic compound in the method (A),
Condensed polycyclic hydrocarbon obtained by condensing two or more monocyclic hydrocarbon compounds having three or more membered rings such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene, naphthacene, picene, perylene, pentaphene, and pentacene. Compounds; or derivatives of the above compounds such as carboxylic acids, carboxylic anhydrides, carboxylic acid imides; various pitches containing a mixture of the above compounds as a main component; indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole , Acridine, phenazine, phenanthridine such that at least two heterocyclic monocyclic compounds having three or more members are bonded to each other or one or more monocyclic hydrocarbon compounds having three or more members are bonded to each other. A condensed heterocyclic compound consisting of 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 carboximides,
For example, 1,2,4,5-tetracarboxylic acid, its dianhydride or its derivative such as diimide can be mentioned.

The above pitch will be described in more detail below.
Examples thereof include ethylene heavy end pitch, crude oil pitch, coal pitch, asphalt cracking 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 a flow of an inert gas, etc., and the quinoline insoluble content is preferably 80% or more, more preferably 90%.
The mesophase pitch of 95% or more can be used.

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

To form the surface carbonaceous material (S) on the carbonaceous material (N) thus synthesized, for example, (1) the surface of the carbonaceous material (N) serving as the nucleus is coated with an organic compound. A method of post-carbonization to form a carbonaceous material (S) in the surface layer,
(2) The organic compound is carbonized on the surface of the carbonaceous material (N) to form the carbonaceous material (S), and the specific surface area (U) of 1/2 or less of the specific surface area U (N) of the carbonaceous material (N) as it is. Or (3) a method of carbonizing an organic compound on the surface of a carbonaceous material (N) to form a carbonaceous material (S) and then performing a pulverization step. it can. At this time, in any of the methods, the specific surface area U of the multi-layered carbonaceous material is calculated as the specific surface area U of the core carbonaceous material (N).
It is half or less than (N). That is, U (N) ≧ 2
U, 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 the carbonaceous material (N). By heating, the organic solvent is evaporated, the organic compound is coated on the surface of the carbonaceous material (N), and then carbonized by heating. Then, it is heated and decomposed to form a carbonaceous material in the surface layer. Examples of organic compounds include aromatic monocyclic hydrocarbons such as benzene and toluene, naphthalene, phenanthrene, anthracene, triphenylene,
Carboxylic acids of condensed polycyclic hydrocarbons such as pyrene, chrysene, naphthacene, picene, perylene, pentaphene and pentacene, carboxylic acid anhydrides, derivatives such as carboxylic acid imides, three-members such as indole, isoindole and quinoline Derivatives such as carboxylic acids, carboxylic acid anhydrides, and carboxylic acid imides of heterocyclic compounds having a ring or more 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. As the organic polymer, cellulose; phenol resin; acrylic resin such as polyacrylonitrile and poly (α-halogenated acrylonitrile); polyamideimide resin; polyamide resin; and the like can be used. (1-3) The surface of the carbonaceous material (N) is covered with a condensed polycyclic hydrocarbon, a heteropolycyclic compound or the like. Then, it heats and a carbonaceous material (S) of a surface layer is formed in a liquid phase. The above-mentioned pitch is preferably used as the condensed polycyclic hydrocarbon.
Particularly in this method, it is preferable to form carbonaceous material (S) by promoting carbonization through a liquid crystal state called mesophase.

The thermal decomposition temperature for forming the surface layer is usually lower than the temperature for synthesizing the carbonaceous material serving as a nucleus, and is 300
The temperature is preferably ~ 2,000 ° C. When the surface of the carbonaceous material (N) serving as the core is coated with an organic compound, after coating until the specific surface area of the carbonaceous material (N) of the core becomes 1/2 or less of the specific surface area U (N). It is preferable to carbonize. It is more preferably 1/3 or less, still more preferably 1/4 or less, particularly preferably 1/5 or less, and most preferably 1/6 or less.

Further, in the synthesis of the carbonaceous material (N) which becomes the core,
It is possible to synthesize a carbonaceous material which becomes a multiphase nuclei in multiple stages by synthesizing an inner nucleus and then an outer nucleus. Similarly, in the synthesis of the carbonaceous material to be the surface layer, the inner surface layer can be synthesized, and the outer surface layer can be synthesized thereon to synthesize the carbonaceous material to be the multiphase surface layer in multiple stages.

In the thus obtained multiphase carbonaceous material, the ratio of the core portion to the surface portion is preferably 35% by weight or more and 90% by weight or less, more preferably 40% by weight or less.
% To 85% by weight, more preferably 45% to 80% by weight, particularly preferably 50% to 75% by weight, most preferably 55% to 70% by weight.
It is less than or equal to weight%.

The surface layer is preferably 10% by weight or more and 65% by weight or less, more preferably 15% by weight or more and 60% by weight or less, further preferably 20% by weight or more and 55% by weight.
It is particularly preferably 25% by weight or more and 50% by weight or less, and most preferably 30% by weight or more and 45% by weight or less.

The thickness of the surface layer that encloses the core is preferably 1
00Å-5 μm, more preferably 200Å-4 μm, further preferably 300Å-3 μm, particularly preferably 5
00Å ~ 2μm, most preferably 700Å ~ 1.5μm
Is.

(Structure of Secondary Battery) Next, an example of a secondary battery using the electrode material of the present invention will be described. The secondary battery is
It has a rechargeable positive electrode and a rechargeable negative electrode, and a separator holding an electrolytic solution is interposed between them.

(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 capable of alloying with an alkali metal or an alloy of an alkali metal. You can also

Examples of the metal which can be alloyed with an alkali metal, preferably a metal which can be alloyed with lithium metal include, for example, 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 are preferable, and Al, Pb, and In are preferable. , Bi and Cd, more preferably Al, Pb and In, particularly preferably A.
1, Pb, and most preferably Al.

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

As an alloy (Li _x M) of the active material,
One or more alloys can be used. As the metal that can be alloyed with the active material, one or more of the above metals M can be used. The metal capable of alloying with an alkali metal or an alloy of an alkali metal is preferably 3% by weight or more and 60% by weight or less, more preferably 5% by weight or more and 50% by weight or less, further preferably, in a mixture with the carbonaceous material of the present invention. It is 7% by weight or more and 45% by weight or less, particularly preferably 10% by weight or more and 40% by weight or less, and most preferably 12% by weight or more and 35% by weight or less. The mixture form of this mixture is as follows: a carbonaceous material, a metal capable of alloying with an alkali metal or an alloy of an alkali metal, and a carbonaceous material (N).
The form in which and are included is most preferable.

The carbonaceous material used in the present invention is usually mixed with a polymer binder to form an electrode material, and then formed into an electrode shape. Examples of the polymer binder include the following. Resinous polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, and cellulose polyvinylidene fluoride. Rubber-like polymers such as styrene / butadiene rubber, isoprene rubber, butadiene rubber, ethylene / propylene rubber. Thermoplastic elastomeric polymers such as styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / isoprene / styrene block copolymers, and hydrogenated products thereof. Soft resinous polymers such as syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (C2 or C4-12) copolymer. A polymer composition having ion conductivity of alkali metal ions, particularly Li ions.

Examples of the above-mentioned ion conductive polymer composition include a polymer compound such as polyethylene oxide, polypropylene oxide, polyepichlorohydrin, polyphosphazene, polyvinylidene fluoride and polyacrylonitrile, and a lithium salt or lithium as a main component. It is possible to use a system in which an alkali metal salt described below is combined, or a system in which an organic compound having a high dielectric constant such as propylene carbonate, ethylene carbonate, or γ-butyrolactone is further mixed. The polyphosphazene preferably has a polyether chain, particularly a polyoxyethylene chain, in the side chain.

The ionic conductivity of such an ion conductive polymer composition at room temperature is preferably 10 ⁻⁸ S · cm ^−1.
Or more, more preferably 10 ⁻⁶ S · cm ⁻¹ or more, further preferably 10 ⁻⁴ S · cm ⁻¹ or more, particularly preferably 10 ⁻³ S.
・ It is cm ^-1 or more. The carbonaceous material used in the present invention and the above-mentioned polymer binder may be mixed in various forms. That is, a form in which both particles are simply mixed, a form in which a fibrous binder is mixed in a form in which the carbonaceous substance particles are entangled, or the above rubber-like polymer, thermoplastic elastomer, soft resin, ion-conducting polymer Examples include a form in which a layer of a binder such as a composition is attached to the surface of carbonaceous material particles.

When a fibrous binder is used, the diameter of the fiber of the binder is preferably 10 μm or less, more preferably 5 μm or less, fibrils (ultrafine fibers), and fibrid (tactile-like ultrafine fibers). Powder with fibrils)
Is particularly preferable. The mixing ratio of the carbonaceous material and the binder is preferably 0.1 to 30 parts by weight, more preferably 0.5 to 100 parts by weight of the carbonaceous material.
20 parts by weight, more preferably 1 to 10 parts by weight.

The carbonaceous material used in the present invention is a mixture with the above-mentioned binder; or a mixture containing a metal capable of forming an alloy with the active material or an alloy of the active material and the metal. An electrode molded body can be obtained by molding the electrode material into a shape of the electrode as it is by a method such as roll molding or compression molding. Alternatively,
These components may be dispersed in a solvent and applied to a metal collector or the like. The shape of the electrode molded body is a sheet shape,
It can be set arbitrarily such as pellets.

An alkali metal as an active material, preferably lithium metal, is added to the electrode molded body thus obtained.
It can be loaded prior to or during assembly of the battery. As a method of supporting the active material on the carrier,
There are chemical methods, electrochemical methods, and physical methods.
For example, a method of immersing an electrode molded body in an electrolytic solution containing a predetermined concentration of an alkali metal cation, preferably Li ions, and using lithium as a counter electrode to electrolytically impregnate the electrode molded body as an anode, and an electrode molded body In the process of obtaining, a method of mixing an alkali metal powder, preferably a lithium powder, can be applied.

Alternatively, a method of electrically contacting the lithium metal and the electrode molded body may be used. In this case, it is preferable to bring the lithium metal and the carbonaceous material in the electrode molded body into contact with each other via the lithium ion conductive polymer composition. The amount of lithium thus preliminarily supported on the electrode molded body is preferably 0.030 to 0.250 part by weight, and more preferably 0.0
60 to 0.200 parts by weight, more preferably 0.070
~ 0.150 parts by weight, particularly preferably 0.075 ~
0.120 parts by weight, most preferably 0.080-0.1
It is 00 parts by weight. The electrode of the present invention using such a carbonaceous material is usually used as a negative electrode of a secondary battery and is opposed to the positive electrode via a separator.

(Formation of Positive Electrode) The material of the positive electrode body is not particularly limited, but it is preferably, for example, a metal chalcogen compound which releases or acquires an alkali metal cation such as Li ion in association 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 these. Complex oxides, complex sulfides, and the like. 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 ; TiS 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. In addition, LiCo
Oxides such as _{O 2, WO 3; CuS,} Fe 0.25 V 0.75 S
₂ , sulfides such as Na _0.1 CrS ₂ ; NiPS ₃ , Fe
Phosphorus and sulfur compounds such as PS ₃ ; VSe ₂ , NbSe
A selenium compound such as ₃ can also be used.

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.
Above, particularly preferably 1000 m ² / g or more, most preferably 2000 m ² / g or more carbonaceous material can be used for the positive electrode. Further, a specific surface area of 10 m ² / g or more, preferably 100 m ² / g or more, more preferably 500 meters ² /
A carbonaceous material of g or more, particularly preferably 1000 m ² / g or more, and most preferably 2000 m ² / g or more can be used for the positive electrode.

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

As the electrolytic solution, a mixed solvent containing 5 vol% or more and less than 60 vol% of ethylene carbonate, 3 vol% or more and 85 vol% or less of chain ether or cyclic ether or chain ester compound, and not containing 30 vol% or more of propylene carbonate is used. An electrolytic solution obtained by dissolving an alkali metal salt or a quaternary ammonium salt is used.

As the electrolyte, LiClO ₄ , LiPF _4
6 , LiAsF ₆ , LiBF ₄ , LiSO ₃ CF ₃ , L
An alkali metal salt such as iN (SO ₂ CF ₃ ) ₂ or a tetraalkylammonium salt can be used. Alkali metal salts are preferred. The concentration is preferably 0.2 mol / l or less, more preferably 0.3 mol / l or more and 1.9 mol / l or less.

The solvent for dissolving the electrolyte is at least 2
A mixed solvent consisting of seed solvents is used, one of which is
Ethylene carbonate, ethylene carbonate in the mixed solvent is 5 vol% or more and less than 60 vol%, preferably 7 vol% or more and less than 50 vol%, more preferably 10 vol% or more and 45 vol% or less, further preferably 12 vol% or more and 40 vol% or less, particularly It is preferably 15 vol% or more and 40 vol% or less.

Further, the mixed solvent may contain an ether compound, a chain ether or a cyclic ether or a chain ester compound, and these compounds in the mixed solvent are
3 vol% or more and 85 vol% or less, preferably 10 vo
1% or more and 85 vol% or less, more preferably 15 vol
% Or more and 80 vol% or less, more preferably 18 vol
% Or more and 70 vol% or less, particularly preferably 20 vol
% Or more and 60 vol% or less, most preferably 30 vol%
It is 50 vol% or less.

Examples of chain ether compounds include 1, 2
-Dimethoxyethane, examples of cyclic ether compounds include crown ethers (12-crown-4 etc.), 1,
2, dimethyltetrahydrofuran, dioxolane, tetrahydrofuran and the like can be mentioned. Examples of chain ester compounds include diethyl carbonate.

Further, the mixed solvent may contain less than 30 vol% of propylene carbonate. The propylene carbonate in the mixed solvent is preferably less than 25 vol%, more preferably less than 20 vol%, and 10 vol%.
%, More preferably less than 5% by volume, particularly preferably less than 5% by volume, and most preferably not contained. Furthermore, cyclic ester compounds other than ethylene carbonate and propylene carbonate, such as γ-butyrolactone, may be contained. In this case, the ratio in the mixed solvent is 70v.
It is preferably ol% or less, more preferably 50 vol% or less, still more preferably 30 vol% or less.

In a secondary battery thus constructed, 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 (particularly Lithium ions are preferable), and the active material ions are released during discharge, so that the charge / discharge electrode reaction proceeds. In the positive electrode, active material ions are released from the positive electrode body during charging,
The active material ions are doped at the time of discharging, and the electrode reaction of charging / discharging proceeds.

Further, in the secondary battery using the above-mentioned conductive polymer or the carbonaceous material having a large specific surface area for the positive electrode and the carbonaceous material of the present invention for the negative electrode, the cation in the electrolytic solution is charged in the negative electrode during charging. Are doped, and cations in the negative electrode body are released at the time of discharge, so that the electrode reaction of charge and discharge proceeds. On the other hand, in the positive electrode, the anions in the electrolytic solution are doped at the time of charging, and the anions in the positive electrode body are released at the time of discharging, so that the electrode reaction of charging / discharging proceeds.

The secondary secondary battery using the carbonaceous material of the present invention as the negative electrode exhibits excellent balance of secondary battery capacity and long-term charge / discharge cycle characteristics and excellent safety characteristics. In the present invention, each measurement of X-ray wide angle diffraction, density, etc. was carried out by the following methods.

Wide-angle X-ray diffraction (1) Surface spacing of (002) plane (d₀₀₂) And (110)
Face spacing (d₁₁₀) If the carbonaceous material is powder,
If it is in the form of small pieces, it is pulverized in an agate mortar and carbonized.
High-purity silicon powder for X-ray standard, about 15% by weight of the product
The powder is mixed as an internal standard substance and packed in a sample cell. Gu
The CuKα line monochromated with the LaFight monochromator
Wide-angle as a radiation source by the reflection diffractometer method
X-ray diffraction curve is measured. To correct the curve, the so-called
Related to rents, polarization factors, absorption factors, atomic scattering factors, etc.
The following simple method is used without correction. That is (00
2) and (110) diffraction based baselines
And re-plot the real intensity from the baseline.
Then, the correction curves for the (002) plane and the (110) plane are obtained.
It The angle drawn to two-thirds the peak height of this curve
Find the midpoint of the line segment where the line parallel to the degree axis intersects the diffraction curve,
Correct the angle of the midpoint with the internal standard and set it to twice the diffraction angle.
Then, from the wavelength λ of the CuKα ray to the Bragg equation of the equation (3)
Therefore d₀₀₂And d ₁₁₀Ask for.

[0075]

[Equation 2] λ: 1.5418Å θ, θ ': d ₀₀₂ , d ₁₁₀ equivalent diffraction angle

(2) Size of crystallites in the c-axis and a-axis directions: Lc; La In the corrected diffraction curve obtained in the previous section, the so-called half-value width β at half the peak height was used to determine the c-axis. And the size of the crystallite in the a-axis direction is calculated by the following equation.

[0077]

[Equation 3] As the shape factor K, 0.90 was used. λ, θ and θ ′ have the same meanings as in the previous section.

True Density Measured using a gas replacement method with helium gas using a multi-pynometer manufactured by Yuasa Ionics.

Example 1 (1) Formation of Negative Electrode In X-ray wide angle diffraction, the true density was 2.25 g / cc, d
₀₀₂ is 3.36Å, average particle size is 17 μm, and specific surface area is 8.
7 m ² / g of carbonaceous material was heated with stirring in a solution of pitch (a mixture of condensed polycyclic hydrocarbon compounds) dissolved in a toluene solvent to coat pitch on the surface of the carbonaceous material particles. ..

Next, under nitrogen flow, the temperature was raised to 1400 ° C. at a heating rate of 20 ° C./min, and the mixture was held at 1400 ° C. for 30 minutes to carbonize it, form carbonaceous material particles having a multiphase structure, and then pulverize lightly. To obtain particles having an average particle diameter of 24 μm. As a result of the measurement, the ratio of the carbonaceous material in the surface layer was 40 parts by weight with respect to 100 parts by weight of the carbonaceous material serving as the core. Further, in the Raman spectrum analysis using an argon ion laser beam (5145Å), the R was 0.47.

The true density was 2.17 g / cc and the BET specific surface area was 1.9 m ² / g. D ₀₀₂ in X-ray wide angle diffraction
Had two peaks of 3.36Å and 3.48Å, and the peak intensity ratio (I _3.49 Å / I _3.36 Å) of both was 0.015. In addition, the total pore volume in the range of 10 Å or more and 300 Å or less measured by the constant volume method is 2.0 × 1
It was 0 ^-2 ml / g.

Polyethylene 6 was added to 94 parts by weight of this carbonaceous material.
Parts by weight were mixed and compression-molded into a pellet having a diameter of 16 mm. This was heated to 130 ° C. in vacuum and dried to form a negative electrode.

(2) Formation of positive electrode: V ₂ O ₅ -P ₂ O _{5 (} 500 mg), polytetrafluoroethylene (25 mg) and carbon black (25 mg) were kneaded to form a sheet, and then 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 assembly of the secondary battery cell, ethylene carbonate (40v) containing 1.0 mol / liter of LiClO ₄ was used.
ol%) / diethyl carbonate (60 vol%) solution with a positive electrode of 1.
It was precharged at 2 mA for 15 hours. Similarly, the negative electrode was also precharged at 1.2 mA for 7 hours.

LiClO ₄ was added to ethylene carbonate (40 vol%) and diethyl carbonate (60 v).
A polypropylene separator impregnated with an electrolytic solution dissolved in a mixed solvent of 1 mol / liter) was interposed between both electrodes to form a secondary battery cell. This secondary battery cell was placed in a constant temperature bath at 10 ° C., and the operation of charging between both electrodes up to 3.3 V with a constant current of 1.5 mA and discharging down to 1.8 V was repeated. Table 1 shows the characteristics of the 2nd and 20th cycles.
It was shown to.

Comparative Example 1 (1) Formation of Negative Electrode In X-ray wide-angle diffraction, the true density was 2.25 g / cc, d
₀₀₂ is 3.35Å, L _C is 1000Å or more, R value is almost 0 in Raman spectrum separation, and average particle size is 1
Graphite particles having a single-phase structure of 7 μm were mixed with 94 wt% and polyethylene 6 wt% to form a negative electrode 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 constructed in the same manner as in Example 1, the secondary battery characteristics thereof were evaluated, and summarized in Table 1.

(Comparative Example 2) An electrolytic solution prepared by dissolving 1 mol / l of LiClO ₄ in ethylene carbonate (30 vol%) and propylene carbonate (70 vol%) was used.
The other structure constituted the same secondary battery cell as Example 1.
The secondary battery characteristics were evaluated and summarized in Table 1.

[0088]

[Table 1]

Claims (2)

[Claims] 1. An electrode material comprising a carbonaceous material that satisfies the following (1). (1) Carbonaceous material particles having a multiphase structure, wherein the carbonaceous material particles have a peak of (002) plane spacing d ₀₀₂ of 3.35 Å or more and 3.37 Å or less by X-ray wide angle diffraction, In the Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145Å, the following R value was 0.11.
A carbonaceous material having a specific surface area (Sm ² / g) and a true density (ρg / cm ³ ) of S ≦ 41-15ρ, which is 1.0 or more and 1.0 or less. R = I _B / I _A (in the Raman spectra, 1580
Having a peak P _{A in} the range of ˜1620 cm ⁻¹ ,
It has a peak P _{B in} the range of 1370 cm ^-1 , and the intensity of P _A is I _A and the intensity of P _B is I _B ) 2. A secondary battery comprising a rechargeable positive electrode, a rechargeable negative electrode, and a non-aqueous electrolyte solution in which an electrolyte salt is dissolved, wherein the negative electrode is the carbon according to claim 1. Secondary battery characterized by containing 50 to 98% by weight of a substance and the electrolyte solution satisfying the following (2) (2) 5 vol% or more of ethylene carbonate, 60v
An electrolytic solution obtained by dissolving an alkali metal salt or a quaternary alkylammonium salt in a mixed solvent containing less than 1% by weight and a cyclic ether or chain ester compound in an amount of 3% by volume or more and 85% or less.