JP3142166B2 - Non-aqueous solvent secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery. More particularly, the present invention relates to a secondary battery having a high capacity, excellent charge / discharge characteristics and high safety, in which the active material is an alkali metal, particularly preferably a lithium metal.

[0002]

2. Description of the Related Art In recent years, there has been a great deal of research and development aimed at improving the performance of batteries. One of them is a study on a rechargeable secondary battery using electrochemical doping using a carbon material as an electrode. When graphite is used as a carbon electrode as a negative electrode, cations such as Li ⁺ ions can be doped between the layers, but are very unstable in the electrolyte and react with the electrolyte to form an electrode material. (J. Electrochem. Society. 125, 687 (1978),). On the other hand, a conductive polymer such as polyacetylene is used as an electrode,
There is also much interest in the study of rechargeable secondary batteries using electrochemical doping. For example,
JP-A-57-121168 proposes a battery using an acetylene polymer. However, polyacetylene is unstable, such as being oxidized and degraded in the air, and degrades by reacting with a small amount of water or oxygen contained in a solvent, resulting in poor stability as an electrode. In particular, polyacetylene used as a negative electrode is severely deteriorated in an electrolytic solution. Therefore, a battery using polyacetylene for both electrodes has high self-discharge and poor charge / discharge charge efficiency, making it difficult to obtain a high-performance and highly reliable battery.

In a battery using Li metal as a negative electrode and polyacetylene as a positive electrode, problems such as charge efficiency in charge and discharge are improved as compared with a battery using polyacetylene for both electrodes. Again, the charge / discharge cycle characteristics are extremely poor. That is, when the battery is discharged, Li is converted to Li ions from the negative electrode body and moves into the electrolytic solution, and when charged, the Li ions are converted to metal Li and electrodeposited on the negative electrode body again. And the metal Li deposited with it
Means dendrite-like. Since the dendritic Li is an extremely active substance, it decomposes the electrolytic solution, resulting in a disadvantage that the charge / discharge cycle characteristics of the battery deteriorate. As this grows further,
Finally, there is a problem that the dendritic metal Li electrodeposit penetrates the separator and reaches the positive electrode body, causing a short circuit phenomenon. In other words, there is a problem that the charge / discharge cycle life is short. In addition, the conductive polymer has a disadvantage that it lacks the doping amount of lithium ions, that is, the electrode capacity and the stable charge / discharge characteristics. In order to avoid such a problem, an attempt has been made to constitute the negative electrode by using a carbonaceous material obtained by calcining an organic compound as a carrier and carrying Li or an alkali metal mainly composed of Li on the carrier. By using such a negative electrode body, the charge / discharge cycle characteristics of the secondary battery have been dramatically improved, but on the other hand, the capacity of the secondary battery has not been sufficiently large. An object of the present invention is to provide a secondary battery having a large battery capacity and excellent charge / discharge cycle characteristics under such circumstances.

The inventor of the present invention has conducted intensive studies in order to solve the above-mentioned problems, and as a result, a specific carbonaceous material described later has been used for the negative electrode.
It has been found that the combination of a specific electrolytic solution is extremely effective for the above purpose, and the present invention has been accomplished. That is, the non-aqueous solvent secondary battery of the present invention is a rechargeable positive electrode, a rechargeable negative electrode and a secondary battery provided with an electrolytic solution obtained by dissolving an electrolyte salt in a non-aqueous solvent, the negative electrode is A carbonaceous material (A) satisfying the condition (1) as a main component,
The present invention provides a non-aqueous solvent secondary battery, characterized in that the electrolyte satisfies the following condition (2). (1) (b) have a multi-phase structure; (b) the H / C atomic ratio is 0.08 or less, (c) spacing of X-rays by the wide-angle diffraction (002) plane d ₀₀₂
Is 3.35 ° or more and less than 3.43 °, and d ₀₀₂ is 3.
(D) In Raman spectrum analysis using argon ion laser light having a wavelength of 5145 °, the G value represented by the following formula is 0.4 or more;

[0005]

(Equation 2)

(2) The cyclic ester compound is used in an amount of 8 to 90 vo.
An electrolytic solution obtained by dissolving an electrolyte salt in a mixed solvent containing l% and 10 to 85 vol% of an ether compound or a chain ester compound. Hereinafter, the present invention will be described in more detail. The secondary battery of the present invention has a rechargeable positive electrode and a rechargeable negative electrode,
A separator for holding the electrolyte is interposed between the two. [Negative electrode] The following carbonaceous material (A) is used for the negative electrode as a main component.
That is, the carbonaceous material (A) has a multiphase structure composed 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 has specific physical characteristics. ing.

[Multiphase Structure] FIG. 1 schematically shows the carbonaceous material (A). In FIG. 1, a
Has a high degree of graphitization (d ₀₀₂ is 3.35% or more and 3.43%).
This is a model of a multiphase structure in which carbon having a low degree of graphitization is formed by carbon as an inner core and its surface layer. b is a model of a multiphase structure in which a plurality of carbons having a high degree of graphitization are used as an inner core, and carbons having a lower degree of graphitization are included therein. c
Is a model of a multi-phase structure in which a plurality of fibrous carbons having a high degree of graphitization are used as an inner core and carbons having a lower degree of graphitization are included. d is a model of a multiphase structure in which fibrous carbon having a high degree of graphitization is used as an inner core and carbon having a lower degree of graphitization is included. In the figure, 1 indicates a high degree of graphitization (d
₀₀₂ is 3.35% or more and less than 3.43%) carbon, and 2
Is a carbon having a degree of graphitization lower than 1 described above.

[H / C atomic ratio] The carbonaceous material (A) used for the negative electrode of the present invention has an H / C atomic ratio of 0.08 or less,
Preferably 0.07 or less, more preferably 0.06 or less,
More preferably 0.05 or less, particularly preferably 0.0.
4 or less, most preferably 0.03 or less. This H /
The C atomic ratio is given as an average value of the H / C atomic ratio of the entire carbonaceous material included in the multiphase structure including the surface layer and the nucleus.

[X-ray wide angle diffraction] The carbonaceous material (A) of the present invention
Has at least two peaks in wide-angle X-ray diffraction due to this multiphase structure. That is, as a peak of the X-ray wide-angle diffraction corresponding to the carbonaceous material in the above-described core portion, the (002) plane spacing d ₀₀₂ is 3.35 ° or more and 3.4 or more.
Less than 3 °, preferably 3.35 to 3.42 °, more preferably 3.35 to 3.41 °, even more preferably 3.35 to
It has a peak which is 3.40 °, particularly preferably 3.35-3.38 °, most preferably 3.36-3.37 °. The crystallite size (Lc) in the C-axis direction corresponding to this peak is preferably 100 ° or more, more preferably 150 ° or more, further preferably 180 ° or more, particularly preferably 220 to 1000 °, and most preferably 2 ° or more.
50-800 °. Further, as a peak of X-ray wide-angle diffraction corresponding to the carbonaceous material in the surface layer, d ₀₀₂ is 3.43 ° or more, more preferably 3.44 ° or more, further preferably 3.45 to 3.80 °, particularly preferably 3.46 °. ~ 3.7
It has a peak that is between 0 ° and most preferably between 3.47 and 3.67 °. Further, Lc corresponding to this peak is preferably less than 100 °, more preferably 70 ° or less, further preferably 7 to 50 °, particularly preferably 12 to 40 °,
Most preferably, it is 15 to 35 °. The peaks in the X-ray wide-angle diffractogram were separated by approximating the profile of each peak with an asymmetric Pearson VII function, and the least squares method was performed by applying the Gauss-Jordan method.

The peak intensity ratio I _(3.43-) / I _{(3.35-3.43) of the} two peaks thus separated is preferably 0.001 or more, more preferably 0.002 to 0.08, It is more preferably from 0.003 to less than 0.030, particularly preferably from 0.004 to 0.029, and most preferably from 0.004 to 0.027. Here _{I (3.43~)} is the peak intensity of the peak d ₀₀₂ is more than _3.43Å, I _{(3 .35~3.43)} is d ₀₀₂ is a peak intensity of a peak of less than 3.35 Å 3.43A . The ratio I _{(2θ = 25 )} of the diffraction intensity I _{(2θ = 25} ° ₎ at 2θ (diffraction angle) = 25.0 ° to I _{(3.35 to 3.43)}
° ₎ / I _{(3.35 to 3.43)} is preferably 0.001 or more, more preferably 0.002 to 0.08,
It is more preferably 0.003 or more and less than 0.030, particularly preferably 0.004 to 0.029, and most preferably 0.005 to 0.027.
When the core carbonaceous material further comprises two or more phases, d ₀₀₂ is 3.35 ° or more and 3.4 or more in X-ray wide-angle diffraction.
It has two or more peaks in a region less than 3 °. When the surface carbonaceous material further comprises two or more phases, it has two or more peaks at d ₀₀₂ of 3.43 ° or more in X-ray wide-angle diffraction. In this case, d _{( 002 )} is 3.43Å
_Assuming that the sum of the peak intensities of the above peaks and I _(3.35 to _3.43) is the sum of the peak intensities of d ₀₀₂ equal to or more than 3.35 ° and less than 3.43 °, the intensity ratio I _(3.43) / I
_{(3.35 to 3.43)} is preferably in the above-mentioned range of values.

Further, I _(3.43〜 , integrated intensity) is defined as the sum of integrated intensity of peaks at d ₀₀₂ of 3.43 ° or more, and I
_{(3.35 to 3.43} , integrated intensity) d ₀₀₂ is 3.35 to 3.43
Assuming that the sum of the integrated intensities of the peaks of Å is
_(3.43- , integral intensity) / I _(3.35-3.43 , integral intensity) is preferably 0.001-0.8, and _0.002-
More preferably 0.60 to 0.003 to 0.5.
It is more preferably 0, particularly preferably 0.004 to 0.40, and most preferably 0.005 to 0.30.

[Raman spectrum] Further, the carbonaceous material (A) used in the present invention was analyzed by Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 °.
It has the following spectral features: Hereinafter, spectra and peaks are Raman spectra under the above conditions unless otherwise specified. That is, 1340 to 13
The integrated intensity of spectrum in the range of 80 cm ^-1 and I _B,
If the integrated intensity of spectrum in the range of 1580～1620Cm ^-1 was I _A, G value is 0.4 or more represented by the following formula, preferably 0.5 or more, more preferably 0.6 or more,
More preferably 0.7 to 1.8, particularly preferably 0.7 to 1.8.
It is from 8 to 1.5, most preferably from 0.9 to 1.3.

[0013]

(Equation 3)

The fine structure of the carbonaceous material forming the surface layer contributes to the Raman spectrum. That is, 1580
Peak P _{A in} the range of １６1620 cm ⁻¹ , 1340 to 138
It has a peak P _{B in} the range of 0 cm ^-1 . P _A is a peak observed corresponding to a crystal structure that grows and forms with the spread of the aromatic ring network plane, and P _B is a peak corresponding to a disordered amorphous structure. Integrated intensity of spectrum corresponding to the peak of the two I _B, the ratio of _{I A G = I B / I} A) is a carbonaceous material,
That is, the larger the ratio of the amorphous structure portion in the surface layer such as carbonaceous particles and carbonaceous fibers, the larger the value. Further, the carbonaceous material (A) used in the present invention preferably has the following Raman spectrum. That is,
Position of P _A varies depending on the degree of completeness of a crystalline portion. Position of P _A of the carbonaceous material to be used in the present invention is a 1580～1620Cm ^-1 as described above, preferably 1585～1620Cm ^-1, more preferably 1590-1
620 cm ^-1 , more preferably 1595 to 1615 c
m ^-1 , particularly preferably in the range of 1600 to 1610 cm ^-1 . The half width at half maximum of the peak is narrower as the higher order structure of the carbonaceous material is more uniform. P _A of the carbonaceous material to be used in the present invention
The half-value half-width, preferably 25 cm ^-1 or more, more preferably 27cm ^-1 or more, more preferably 30-60 cm ^-1, particularly preferably 35~55cm ^-1. P _B is usually 1
It has a peak at 360 cm ^-1 . Half width at half maximum of the P _B is preferably 20 cm ^-1 or more, more preferably 20~150c
m ^-1 , more preferably 25-125 cm ^-1 , particularly preferably 30-115 cm ^-1 , most preferably 40-110
cm ^-1 .

[Other Preferred Properties] (True Density) The true density of the carbonaceous material (A) of the present invention is given as an average of the true densities of the entire carbonaceous material contained in the multiphase structure including the surface layer and the nucleus. Can be Carbonaceous material (A) of the present invention
True density of preferably 2.00 g / cm ³ or more, more preferably 2.05 g / cm ³ or more, more preferably 2.10
g / cm ³ or more, particularly preferably 2.15 g / cm ³ or more,
Very preferably 2.18 to 2.25 g / cm ³ , most preferably 2.20 to 2.24 g / cm ³ .

(Differential heat) In the differential thermal analysis, the carbonaceous material used in the present invention has an exothermic behavior in a wide temperature range where at least two exothermic peaks overlap according to the above-mentioned multiphase structure. Is shown. Preferably, it is in a temperature range of 100 ° C. or more, more preferably in a temperature range of 150 ° C. or more, still more preferably in a temperature range of 200 ° C. or more, particularly preferably in a temperature range of 250 to 500 ° C., and most preferably 280 ° C. It shows an exothermic behavior in a temperature range of up to 400 ° C. The end temperature of the exothermic peak is preferably 800 ° C. or higher, more preferably 810 ° C. or higher, and further preferably 8 ° C. or higher.
20-980 ° C, particularly preferably 830-970 ° C,
Most preferably, it is 840-950 ° C. The starting end temperature of the exothermic peak is preferably 700 ° C or lower, more preferably 680 ° C or lower, even more preferably 550 to 680 ° C,
Particularly preferably 570-670 ° C, most preferably 5
80-650 ° C. The exothermic peak temperature is 650.
To 840 ° C., preferably 660 to 835 ° C., more preferably 670 to 830 ° C., particularly preferably 680 to 820 ° C., and most preferably 690 to 810 ° C. preferable.

[Shape of Carbonaceous Material (A)] The carbonaceous material (A) used in the present invention may have any shape such as a particle shape or a fibrous shape. Particulate is particularly preferred. In the case of particles, the volume average particle diameter is preferably 200 μm or less, more preferably 100 μm or less, and still more preferably 0.5 to 0.5 μm.
It is 80 μm, particularly preferably 1 to 50 μm, most preferably 2 to 30 μm. When fibrous, the diameter is preferably 0.5 to 50 μm, more preferably 0.8 to 30 μm
And more preferably 1 to 25 μm, particularly preferably 2 to 20 μm, and the length is preferably 10
mm or less, more preferably 5 mm or less, still more preferably 0.1 mm to 2 mm, and particularly preferably 0.2 mm to 1 mm.
It is. The carbonaceous material used in the present invention is BET.
The specific surface area measured using the method is preferably 0.1 to 1
00 m ² / g, more preferably 0.5 to 50 m ² / g, still more preferably 0.5 to 30 m ² / g, particularly preferably 0.5 to 30 m ² / g.
It is 5 to ²⁰ m ² / g, most preferably 0.5 to 10 mm ² / g.

Further, the carbonaceous material (A) preferably has pores inside (surface layer). The total pore volume and the average pore radius described below are calculated using the constant volume method under the conditions of several equilibrium pressures, the amount of gas adsorbed (or released) on the sample.
Is determined by measuring the amount of gas adsorbed on the sample while measuring. The total pore volume is given by the relative pressure P / _Po = 0.9, assuming that the pores are filled with liquid nitrogen.
Determined from the total amount of gas adsorbed at 95. P: Vapor pressure of the adsorbed gas (mmHg) P _O : Saturated vapor pressure of the adsorbed gas at the cooling temperature (mmHg) From the amount of the adsorbed nitrogen gas (Vads), the pores are filled into the pores using the following equation (1). The total pore volume is determined by converting to the amount of liquid nitrogen (Vliq). Vliq = (Patm · Vads · Vm) / RT (1) where Patm and T are the atmospheric pressure (kgf / c
m ² ) and the absolute temperature (K), and R is a gas constant.
Vm is the molecular volume of the adsorbed gas (34.7 cm ^{3 for} nitrogen)
/ Mol). The carbonaceous material used in the present invention has a total pore volume of 1.5 × 10 ⁻³ ml determined as described above.
/ G or more. More preferably, the total pore volume is 2.0 × 10 ⁻³ ml / g or more, further preferably 3.0 × 10 ⁻³ to 8 × 10 ⁻² ml / g, particularly preferably 4.0 × 10 ^−3. ３3 × 10 ⁻² ml / g. The average pore radius (γp) is calculated from Vliq obtained from the above equation (1),
From the specific surface area S obtained by the BET method, it is determined by calculation using the following equation (2). Here, it is assumed that the pores are cylindrical. γp = 2Vliq / S (2) As described above, the average pore radius (γp) of the carbonaceous material determined from the adsorption of nitrogen gas is preferably 8 to 100 °. The angle is more preferably 10 to 80 °, further preferably 12 to 60 °, particularly preferably 14 to 40 °. Further, the carbonaceous material used in the present invention has a pore volume measured by a mercury porosimeter of preferably 0.05 ml.
/ G or more, more preferably 0.10 ml / g or more, further preferably 0.15 to 2 ml / g, particularly preferably 0.20 to 1.5 ml / g.

[Synthesis of Carbonaceous Material (A)] The carbonaceous material (A) used in the present invention can be synthesized, for example, by the following method. That is, first, the organic compound is decomposed by heating at a temperature of 300 to 3000 ° C. in an inert gas stream or in a vacuum, and carbonized and graphitized,
Synthesize a carbonaceous material as a core. The density of the carbonaceous material as a core is preferably 2.10 g / cm ³ or more, more preferably 2.12 g / cm ³ or more, more preferably 2.15 to 2.
26 g / cm ³ , particularly preferably 2.18 g to 2.25
g / cm ³ , most preferably 2.20 to 2.24 g / cm ³
It is. Natural graphite, artificial graphite, or vapor-grown graphite whiskers can also be used as the core. The carbonaceous material serving as the nucleus can have any shape such as a particle shape and a fiber shape, but is preferably a particle shape, a fiber shape, and particularly preferably a particle shape. Particles of the carbonaceous material serving as the core preferably have a volume average particle size of 0.2 to 100 μm, more preferably 1 to 80 μm, further preferably 2 to 50 μm, particularly preferably 3 to 30 μm, and most preferably 4 to 20 μm.
It is. The average diameter of the core carbonaceous material fiber is
Preferably 0.5 to 20 μm, more preferably 1 to 10
μm, and more preferably 2 to 8 μm. The starting material for obtaining the carbonaceous material serving as the core of the present invention is a three- or more-membered monocyclic carbon such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene, naphthacene, picene, perylene, pentaphen and pentacene. A condensed polycyclic hydrocarbon compound obtained by condensing two or more hydrogen compounds with each other; or a carboxylic acid of the above compound,
Derivatives such as carboxylic anhydrides and carboxylic imides;
Various pitches mainly composed of a mixture of the above compounds; indole, isoindole, quinoline, isoquinoline,
At least two or more heterocyclic monocyclic compounds having three or more ring members such as quinoxaline, phthalazine, carbazole, acridine, phenazine, and phenanthridine are bonded to each other, or one or more monocyclic hydrocarbon groups having three or more ring members Condensed heterocyclic compounds formed by bonding to compounds; derivatives of the above compounds such as carboxylic acids, carboxylic anhydrides, and carboxylic imides; and aromatic monocyclic hydrocarbons such as benzene, toluene, and xylene; Derivatives such as carboxylic acid, carboxylic anhydride, and carboxylic imide, for example, derivatives such as 1,2,4,5-tetracarboxylic acid, dianhydride and diimide thereof can be given.

The above-mentioned pitch will be described in more detail.
Ethylene heavy-end pitch generated during the decomposition of naphtha, crude pitch generated during the decomposition of crude oil, coal pitch generated during the pyrolysis of coal, asphalt-decomposed pitch generated by asphalt decomposition, polyvinyl chloride, etc. Pitch generated by thermal decomposition can be cited as an example. In addition, these various pitches are further heated under an inert gas flow or the like, so that the quinoline-insoluble content is preferably 80% or more, more preferably 90% or more, and still more preferably 95% or more mesophase pitch. Can be. Further, aliphatic saturated or unsaturated hydrocarbons such as propane and propylene are also used. Further, conjugated resins such as acrylic resins such as polyacrylonitrile and poly (α-halogenated acrylonitrile), halogenated vinyl resins such as polyvinyl chloride, polyvinylidene chloride and chlorinated polyvinyl chloride, polyacetylene and poly (p-phenylene) Organic polymer compounds such as a series resin can be exemplified. Alternatively, a carbonaceous material such as carbon black or coke as a starting material may be further heated to appropriately promote carbonization to be used as a core of the carbonaceous material used in the present invention. As described above, natural graphite or artificial graphite can be used as the carbonaceous material forming the nucleus.

Then, using the carbonaceous material obtained as described above as a nucleus, the organic compound is decomposed by heating under an inert gas stream, carbonized, and a new carbonaceous material is deposited on the surface of the nucleus. A surface layer is formed. On the surface of the core carbonaceous material,
As a method for forming the surface layer, there are the following methods, which can be arbitrarily selected. (1) A relatively low-molecular organic compound, for example, a paraffin, an olefin, or an aromatic compound having about 20 carbon atoms or less is thermally decomposed to deposit a carbonaceous material in a surface layer. Specifically, propane, aliphatic saturated or unsaturated hydrocarbons such as propylene, benzene, aromatic monocyclic hydrocarbons such as toluene, naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene, naphthacene,
Carboxylic acids, carboxylic anhydrides of fused polycyclic hydrocarbons such as picene, perylene, pentaphene, pentacene,
Derivatives such as carboxylic acid imides and derivatives such as carboxylic acids, carboxylic anhydrides, and carboxylic imides of heteropolycyclic compounds having three or more membered rings such as indole, isoindole, and quinoline can be given. (2) The surface of the carbonaceous material serving as a nucleus is coated with an organic polymer compound, and thermally decomposed in a solid phase to form a carbonaceous material. Organic polymers such as cellulose; phenolic resins; acrylic resins such as polyacrylonitrile and poly (α-halogenated acrylonitrile); polyamideimide resins; polyamide resins; (3) Condensed polycyclic hydrocarbons, heteropolycyclic compounds, and the like are heated and thermally decomposed while in contact with a carbonaceous substance serving as a nucleus in a liquid phase to form a surface carbonaceous substance. It is preferable to use the above-mentioned pitch as the condensed polycyclic hydrocarbon. In a method of heating a condensed polycyclic hydrocarbon particularly on the surface of a carbonaceous material serving as a nucleus, it is preferable to form a carbonaceous material in a surface layer by promoting carbonization via a liquid crystal state called a mesophase. The thermal decomposition temperature for forming the surface layer is usually lower than the temperature for synthesizing the core carbonaceous material, and is 300 ° C.
~ 2000 ° C is preferred. In the synthesis of a core carbonaceous material, an inner core is synthesized, and an outer core is synthesized thereon, whereby a multiphase core carbonaceous material can be synthesized in multiple steps. Similarly, by synthesizing the carbonaceous material as the surface layer, the inner surface layer is synthesized,
An outer surface layer is synthesized thereon, and a carbonaceous material serving as a multiphase surface layer can be synthesized in multiple steps. Thus, in the diffraction diagram of the X-ray wide-angle diffraction, d ₀₀₂ is 3.35 ° or more.
It has at least two diffraction peaks, a peak of less than 43 ° and a peak of 3.43 ° or more, and the integrated intensity ratio G value of the peak of the Raman spectrum is 0.4 or more, and H /
A carbonaceous material having a C atom ratio of 0.08 or less can be obtained.

In the thus obtained carbonaceous material having a multiphase structure, the ratio of the core portion to the surface layer portion is preferably 20 to 95% by weight, more preferably 25% by weight, for the core portion.
-90% by weight, more preferably 30-85% by weight, particularly preferably 35-80% by weight, most preferably 40% by weight.
~ 75% by weight. In addition, the surface portion is preferably
5 to 80% by weight, more preferably 10 to 75% by weight, further preferably 15 to 70% by weight, particularly preferably 2 to 80% by weight.
0-65% by weight, most preferably 25-60% by weight. The thickness of the surface layer surrounding the core is preferably 100 °.
５5 μm, more preferably 200Å-4 μm, further preferably 300Å-3 μm, particularly preferably 500Å.
２2 μm, most preferably 700 ° -1.5 μm.

Further, the carbonaceous material (A) of the present invention can be used as a mixture of a metal capable of forming an alloy with an alkali metal and / or an alloy of an alkali metal. Examples of the metal capable of forming an alloy with an alkali metal, preferably a metal capable of forming an alloy with a lithium metal include aluminum (Al), lead (Pb), zinc (Zn), and tin (Sn). , Bismuth (B
i), indium (In), magnesium (Mg), gallium (Ga), cadmium (Cd), silver (Ag), silicon (Si), boron (B), gold (Au), platinum (Pt), palladium ( Pd), antimony (Sb) and the like, preferably Al, Pb, In, Bi and Cd, more preferably Al, Pb and In, particularly preferably Al and Pb, most preferably Al. As an alloy with an alkali metal, preferably an alloy with lithium metal, assuming that the composition of the alloy is represented by a molar composition Li x M (x is a molar ratio to the metal M), the above-mentioned metal is used as M. The alloy may further contain other elements in the range of 50 mol% or less in addition to the above-mentioned metals.
In ix M, x preferably satisfies 0 <x ≦ 9, more preferably 0.1 ≦ x ≦ 5, still more preferably 0.5 ≦ x ≦ 3, and particularly preferably 0.7 ≦ x ≦ 3.
x ≦ 2. One or more alloys can be used as the active material alloy (Li x M). As the metal that can be alloyed with the active material, one or more of the above metals M can be used. Carbonaceous material (A) of the present invention
The ratio of the metal or alkali metal alloyable with the alkali metal in the mixture of the metal and the alkali metal alloy or the alkali metal alloy is preferably 3 to 60.
% By weight, more preferably 5 to 50% by weight, still more preferably 7 to 45% by weight, particularly preferably 10 to 40% by weight, and most preferably 12 to 35% by weight.

[Production of Electrode] The carbonaceous material (A) 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. Resin-like polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, cellulose, and polyvinylidene fluoride. Rubbery polymers such as styrene / butadiene rubber, isoprene rubber, butadiene rubber, and ethylene / propylene rubber. Styrene-butadiene-styrene block copolymer,
Thermoplastic elastomeric polymers such as hydrogenated products, styrene / isoprene / styrene block copolymers, and hydrogenated products. Soft resinous polymers such as syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (2 or 4 to 12 carbon atoms) copolymer. A polymer composition having ionic conductivity of alkali metal ions, particularly Li ions. Examples of the above-described ion-conductive polymer composition include a polymer compound such as polyethylene oxide, polypropylene oxide, polyepichlorohydrin, polyphosphazene, polyvinylidene fluoride, and boria acrylonitrile, and a lithium salt or an alkali mainly containing lithium. A system in which a metal salt 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 added thereto can be used. The polyphosphazene preferably has a polyether chain, particularly a polyoxyethylene chain in a side chain. The ionic conductivity of such an ionic conductive polymer composition at room temperature is preferably 10 ⁻⁸ S · cm ⁻¹ or more.
It is more preferably at least 10 ^-6 S.cm ^-1 , further preferably at least 10 ^-4 S.cm ^-1 , particularly preferably at least 10 ^-3 S.cm ^-1 . As the mixed form of the carbonaceous material (A) used in the present invention and the above-mentioned polymer binder, various forms can be adopted. That is, a form in which both particles are simply mixed,
A form in which a fibrous binder is entangled with particles of a carbonaceous material, or a layer of a binder such as the above rubber-like polymer, thermoplastic elastomer, soft resin, or ion-conductive polymer composition is formed of carbon. And a form attached to the surface of the particles of the substance.

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 fibrids (tentacle-like ultrafine fibers). Powder with fibrils)
Is particularly preferred. The mixing ratio of the carbonaceous material (A) to the binder is preferably 0.1 to 30 parts by weight, more preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the carbonaceous material (A). Parts, more preferably 1 to 10
Parts by weight. Further, an alkali metal as an active material, in particular, a metal capable of forming an alloy with lithium, for example, aluminum can be mixed with the above mixture. Alternatively, an alloy composed of such a metal and an alkali metal, particularly lithium, for example, a lithium aluminum alloy can be used as a mixture. Such a metal or alloy may be in the form of particles, in the form of a thin layer coated on the surface of a carbonaceous material, or in the form of being contained inside a carbonaceous material. The proportion of the metal or alloy is preferably 70 parts by weight or less, more preferably 5 to 60 parts by weight, and still more preferably 10 to 5 parts by weight, based on 100 parts by weight of the carbonaceous material.
0 parts by weight, particularly preferably 15 to 40 parts by weight.
The carbonaceous material (A) used in the present invention is a mixture with the binder described above; or a mixture of a metal capable of forming an alloy with the active material or an alloy of the metal and the active material. And the electrode material as it is,
The electrode can be formed into a shape of an electrode by a method such as roll forming or compression forming to obtain an electrode formed body. Alternatively, these components may be dispersed in a solvent and applied to a metal current collector or the like. The shape of the electrode molded body can be arbitrarily set, such as a sheet or a pellet.

[Support of Active Material] The thus obtained electrode molded body may be loaded with an alkali metal, preferably a lithium metal, which is an active material, prior to or during assembly of the battery. it can. Examples of a method for supporting the active material on the support include a chemical method, an electrochemical method, and a physical method. 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 ion, and using lithium as a counter electrode, impregnating the electrode with the electrode molded body as an anode, and an electrode molded body A method of mixing an alkali metal powder, preferably a lithium powder, can be applied in the process of obtaining. Alternatively, a method of electrically contacting the lithium metal and the electrode molded body is also used. In this case, it is preferable that the lithium metal and the carbonaceous material in the electrode molded body are brought into contact with each other via a lithium ion conductive polymer plastic. The amount of lithium previously supported on the electrode compact in this manner is preferably 0.030 to 0.250 per 1 part by weight of the carrier.
Parts by weight, more preferably 0.060 to 0.200 parts by weight,
The amount is more preferably 0.070 to 0.150 parts by weight, particularly preferably 0.075 to 0.120 parts by weight, and most preferably 0.080 to 0.100 parts by weight. The electrode of the present invention using such a carbonaceous material (A) is generally used as a negative electrode of a secondary battery, and is opposed to a positive electrode via a separator. As the separator for holding the electrolyte, a nonwoven fabric made of a material having excellent liquid retention properties, for example, a polyolefin such as polyethylene or polypropylene can be used.

[Electrolyte] As the electrolyte used in the secondary battery of the present invention, a mixed solvent containing a cyclic ester compound in an amount of 8 to 90 vol% and an ether compound or a chain ester compound in an amount of 10 to 85 vol% is used. And an electrolyte solution obtained by dissolving an electrolyte salt. Examples of the cyclic ester compound include propylene carbonate, ethylene carbonate, and γ-butyrolactone. Examples of the ether compound to be mixed therewith include 1,2-dimethoxyethane, crown ether (such as 12-crown-4), dioxolan, and tetrahydrofuran. Further, examples of the chain ester compound include diethyl carbonate and the like. The cyclic ester compound in the mixed solvent is
Preferably 10 to 80 vol%, more preferably 15 to 7
0 vol%, more preferably 17 to 60 vol%, most preferably 20 to 55 vol%. The ether compound or chain ester compound in the mixed solvent is preferably from 10 to
85 vol%, more preferably 15 to 80 vol%, still more preferably 18 to 70 vol%, particularly preferably 20 to 6 vol%
0 vol%, most preferably 30 to 50 vol%. As electrolyte salts, LiClO ₄ , LiPF ₆ , LiAsF ₆ , Li
Alkali metal salts such as BF ₄ , LiSO ₃ CF ₃ , and LiN (SO ₂ CF ₃ ) ₂ , and tetraalkylammonium salts can be used.

[Assembly of Secondary Battery] In a secondary battery, for example, a metal net for current collection is placed on a positive electrode can, and a positive electrode material, a separator containing an electrolytic solution, a negative electrode material, a metal Netting, and then layered on it in the order of the negative electrode can,
Assembled by sealing the ends with gaskets. In a battery configured in this manner, for example, a battery using a metal chalcogen compound for the positive electrode and the carbonaceous material of the present invention for the negative electrode, the negative electrode is doped with active material ions (preferably lithium ions) during charging. Then, the active material ions are released at the time of discharge, and the electrode reaction of charge and discharge proceeds. In the positive electrode, active material ions are released from the positive electrode body at the time of charging, and the active material ions are doped at the time of discharging, and the electrode reaction of charging and discharging proceeds. Further, in the battery using the above-described conductive polymer or a 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 doped at the time of charging at the negative electrode, and the discharge is performed. At times, 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, 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, and the electrode reaction of charging and discharging proceeds. The secondary battery of the present invention has the above-described negative electrode and electrolytic solution, and exhibits characteristics excellent in balance between battery capacity and long-term charge / discharge cycle characteristics and excellent safety.

[Measurement method] In the present invention, (a)
Each measurement of X-ray wide-angle diffraction, (b) Raman spectrum, and (c) true density was performed by the following method. (A) X-ray wide-angle diffraction: interplanar spacing of ( ₀₀₂ ) planes (d ₀₀₂ ) If the carbonaceous material is powder, it is powdered in an agate mortar if it is a fine flake, and about 15% by weight based on the sample. X
High-purity silicon powder for a line standard is mixed as an internal standard substance, packed in a sample cell, and a wide angle X-ray diffraction curve is measured by a reflection type diffractometer method using a CuKα ray monochromatized by a graphite monochromator as a source. For the correction of the curve, the following simple method is used without correcting so-called Lorentz, polarization factor, absorption factor, atomic scattering factor and the like. That is, a baseline of a curve corresponding to the (002) diffraction is drawn, and the substantial intensity from the baseline is re-plotted to obtain a correction curve for the (002) plane. The midpoint of the line where the line parallel to the angle axis drawn to two-thirds of the peak height of this curve intersects the diffraction curve is determined, the angle of the midpoint is corrected by the internal standard, and this is repeated. The doubled angle is obtained, and d ₀₀₂ is obtained from the wavelength λ of the CuKα ray by the following Bragg equation.

[0030]

(Equation 4)

(2) Crystallite size in the c-axis direction: Lc In the corrected diffraction curve obtained in the preceding section, the crystallite size in the c-axis direction is calculated using the so-called half width β at half the peak height. Is calculated by the following equation.

[0032]

(Equation 5)

As the shape factor K, 0.90 was used. λ, θ
Has the same meaning as in the previous section. (B) Raman spectrum The measurement was performed using argon laser light as a light source and JASCO NR1000 as a spectroscope. (C) True density The true density was measured using a multi-pycnometer (manufactured by Yuasa Ionics) using a gas replacement method with helium gas. Hereinafter, the present invention will be further described with reference to examples.

[0034]

【Example】

Example 1 (1) Preparation of Negative Electrode A pitch of 10 g was placed in a nitrogen stream at a rate of temperature rise of 2 ° C./min.
The temperature was raised to 500 ° C. and maintained at 500 ° C. for 30 minutes. 10 ° C
/ Minute at 2800 ° C.
Hold for 0 minutes. The carbonaceous material thus formed is:
In the wide-angle X-ray diffraction, d ₀₀₂ was 3.36 °. The carbonaceous material is mechanically pulverized into particles having an average particle diameter of 15 μm, and the particles of the carbonaceous material are heated in a solution in which pitch (a mixture of condensed polycyclic hydrocarbon compounds) is dissolved in toluene, and the pitch is reduced to the carbonaceous material. The material was coated on the surface of the particles. The carbonaceous material obtained by coating the pitch on the surface of the particles of the carbonaceous material serving as the nucleus is placed under a nitrogen gas flow,
The temperature is raised to 1000 ° C. at a rate of 20 ° C./min.
C. for 30 minutes. Thus, a carbonaceous material serving as a surface layer was formed on the surfaces of the particles of the carbonaceous material serving as the nucleus. This was lightly pulverized to obtain a carbonaceous material (A) having an average particle size of 18 μm. For 100 parts by weight of the core carbonaceous material,
The ratio of the carbonaceous material in the surface layer was 35 parts by weight. The G value of the carbonaceous material having the multiphase structure was 0.9 in Raman spectrum analysis using argon ion laser light (5145 °). The H / C atomic ratio was 0.01. In the wide-angle X-ray diffraction, d ₀₀₂
Had two peaks at 3.36 ° and 3.52 °. L _C
Were 465 ° and 27 ° respectively. True density is 2.1
It was 7 g / cm ³ . 93 parts by weight of the carbonaceous material and 7 parts by weight of polyethylene were mixed and compression-molded into a pellet-shaped electrode having a diameter of 16 mm. (2) Preparation of positive electrode _{V 2 O 5 -P 2 O 5} 500mg, polytetrafluoroethylene 25mg, carbon black 25mg kneaded, after a sheet to form a pellet electrode having a diameter of 16 mm. (3) Battery cell configuration and battery performance evaluation Prior to assembling the battery cell, the cathode was treated with 1.0 mol / L L
In a propylene carbonate solution containing iClO ₄ ,
The battery was pre-charged at 1.2 mA for 15 hours using lithium metal as a counter electrode. Similarly, the negative electrode was precharged at 1.2 mA for 7 hours. These two electrodes were prepared by adding 1 mol / l of LiCl ₄ to propylene carbonate (25 vol%), ethylene carbonate (25 vol%) and diethyl carbonate (50 v
ol%) of a battery cell was formed with a polypropylene separator impregnated with a solution of the battery cell dissolved in a mixed solvent of the same. Place this in a (0 ° C) thermostat, and place 1mA between both electrodes.
The operation of charging to a constant current of 3.0 V and discharging to 1.8 V was repeated. Table 1 shows the characteristics of the third and tenth cycles.
It was shown to.

(Comparative Example 1) (1) Preparation of Negative Electrode A carbonaceous material serving as a nucleus was synthesized in the same manner as in Example 1, and this carbonaceous material was used as a negative electrode without forming a carbonaceous material on the surface thereof. Used as an electrode material. This carbonaceous material is d
₀₀₂ is 3.36 °, H / C atomic ratio is 0, G value is 0.18 in Raman spectrum analysis, and average particle size is 15 μm.
m. Using the carbonaceous material particles, a negative electrode was prepared 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 of Battery Cell and Evaluation of Battery Performance A battery cell was configured in the same manner as in Example 1, and its battery performance was evaluated.

Comparative Example 2 In Example 1, propylene carbonate (50 vol.) Was used as the electrolyte in the battery cell.
%) And ethylene carbonate (50 vol%) in the same manner as in Example 1 except that a solution in which LiClO ₄ was dissolved at 1 mol / l in a mixed solvent was used.
Battery cells were prepared and configured, and battery performance was evaluated. The results are shown in Table 1.

[0037]

[Table 1]

[0038]

As described above, according to the present invention, a secondary battery is formed by combining a carbonaceous material (A) having specific characteristics as a negative electrode and a specific non-aqueous electrolyte, thereby achieving a charge / discharge capacity. And a secondary battery with a very small decrease in charge efficiency due to continuous cycle use, and its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 schematically shows a, b, c and d as examples of the structure of a carbonaceous material used as a negative electrode of the present invention.

[Explanation of symbols]

 1 core 2 surface layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-304572 (JP, A) JP-A-3-295178 (JP, A) JP-A-4-368778 (JP, A) International Publication 90/13924 (WO, A1) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01M 4/02-4/04 H01M 4/58 H01M 10/40 JICST file (JOIS) WPI (DIALOG)

Claims (3)

(57) [Claims] 1. A secondary battery comprising a rechargeable positive electrode, a rechargeable negative electrode and an electrolytic solution obtained by dissolving an electrolyte salt in a non-aqueous solvent, wherein the negative electrode satisfies the following condition (1): A non-aqueous solvent secondary battery containing a carbonaceous material (A) as a main component and the electrolyte satisfying the following condition (2): (1) (a) Nucleus and surface layer And the surface layer is organic
The compound has a multi-phase structure formed by heating to decompose and carbonizing ; (b) the H / C atomic ratio is 0.08 or less; (c) the (002) plane by X-ray wide-angle diffraction _D002
Is 3.35 ° or more and less than 3.43 °, and d ₀₀₂ is 3.
(D) In Raman spectrum analysis using argon ion laser light having a wavelength of 5145 °, the G value represented by the following formula must be 0.4 or more: ] (2) 8 to 90 vol% of cyclic ester compound and 10 to 85 v of ether compound or chain ester compound
An electrolytic solution obtained by dissolving an electrolyte salt in a mixed solvent containing ol%. 2. The non-aqueous solvent secondary battery according to claim 1, wherein the organic compound is selected from a condensed polycyclic hydrocarbon and a heteropolycyclic compound. 3. The non-aqueous solvent secondary according to claim 1, wherein a temperature at which the material is decomposed by heating is lower than a temperature at which a carbonaceous material serving as a nucleus is synthesized, and is in a range of 300 to 2,000 ° C. battery.