JPH0793151B2 - Non-aqueous solvent secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a non-aqueous solvent secondary battery, and more specifically, it can be discharged regardless of overcharge and discharge, and its capacity deterioration The present invention relates to a non-aqueous solvent battery that is small, has a significantly long charge / discharge cycle life, is compact, and has a high capacity.

(Prior Art) A non-aqueous solvent secondary battery in which the main component of the positive electrode body is a chalcogen compound of a transition metal such as TiS ₂ and MoS ₂ and the negative electrode body is Li or an alkali metal mainly composed of Li is Due to its energy density, commercialization efforts are being made.

An example of such a secondary battery is shown in FIG. The figure is a vertical cross-sectional view of a button type non-aqueous solvent secondary battery.

In the figure, 1 is a positive electrode body. The positive electrode body 1 is obtained by pelletizing or sheeting a mixture of the powder of the metal chalcogen compound as described above and a binder such as polytetrafluoroethylene.

2 is a separator, for example, a porous polypropylene thin film,
It is made of a material having a liquid retaining property such as polypropylene nonwoven fabric, and is placed on the positive electrode body 1. The separator 2 contains LiClO ₄ , L in an aprotic organic solvent such as propylene carbonate or 1,2-dimethoxyethane.
It is impregnated with a non-aqueous electrolyte solution of a predetermined concentration in which an electrolyte such as iAlO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ is dissolved.

Reference numeral 3 is a negative electrode body placed on the positive electrode body via the separator 2, and is composed of a Li foil or an alkali metal foil mainly containing Li.

The positive electrode body 1, the separator (non-aqueous electrolyte solution) 2, and the negative electrode body 3 together constitute a power generating element. Then, the power generating element is incorporated in a battery container including the positive electrode can 4 and the negative electrode can 5 to assemble the battery. Reference numeral 6 is an insulating packing, and 7 is a current collector interposed between the positive electrode body 1 and the positive electrode can 4. This current collector 7 is usually a nickel net,
The positive electrode body 1 is made of stainless steel metal wire mesh, punched metal, or foam metal, and is pressed onto one surface of the pelletized or sheeted positive electrode body 1.

(Problems to be Solved by the Invention) In the secondary battery having the conventional structure as described above, the following problems occur, and improvement thereof is demanded.

It is a problem based on the fact that the negative electrode body is a Li foil or a foil of an alkali metal mainly containing Li. That is, when the battery is discharged, Li becomes Li ions from the negative electrode body and moves to the electrolytic solution, and at the time of charging, this Li ion becomes metallic Li and is electrodeposited again on the negative electrode body, but when this charging / discharging cycle is repeated. Along with this, the metal Li that is electrodeposited becomes dendrite-shaped and grows.Finally, this dendrite-shaped metal Li electrodeposit penetrates the separator and reaches the positive electrode body, causing a short circuit phenomenon. . In other words,
The problem is that the charge / discharge cycle life is short.

In order to avoid such a problem, it has been attempted to construct a negative electrode body by supporting Li or an alkali metal mainly composed of Li on a support of a carbonaceous material obtained by firing various organic compounds.

By using such a negative electrode body, precipitation of Li dendride came to be prevented, but on the other hand,
This battery has a smaller discharge capacity than a temporary battery of the same size.
Very small, about 1/100, and large self-discharge,
In addition, there are various problems in practical use, such as the operating period of a device equipped with this battery is very short and large current discharge is impossible.

In addition, regarding the positive electrode body, since it has a metal chalcogen compound as a main component, the inactivation of the metal chalcogen compound progresses rapidly as the charge and discharge depth becomes deep, and as a result, several charge and discharge cycles are performed. There is also a problem that the battery capacity is significantly reduced by repetition.

As a result, commercialization of this type of secondary battery has been delayed.

The present invention solves the above-mentioned problems, is small and has a high capacity,
It is an object of the present invention to provide a non-aqueous solvent secondary battery which has excellent charge / discharge cycle characteristics and overcharge / discharge characteristics, has a small self-discharge, and can discharge a large current.

[Configuration of Invention] (Means / Action for Solving Problems) The nonaqueous solvent battery of the present invention has an atomic ratio of H / C of less than 0.15; X
The spacing (d ₀₀₂ ) of the (002) plane is 3.37 by the wide-angle diffraction method.
In the Raman spectrum analysis using an argon laser beam having a crystallite size (Lc) in the C-axis direction of 150 Å or less and a wavelength of 5145 Å or more, the following formula: A non-aqueous solvent secondary battery comprising a negative electrode body composed of a fired organic material having a G value of less than 2.5; a positive electrode body mainly composed of amorphous V ₂ O ₅ ; and Li as an active material. When the battery voltage is 2.0 V or higher, the positive electrode body contains 0.4 to 0.8 mol amount of Li with respect to 1 mol amount of V ₂ O ₅ , and when the battery voltage is less than 2.0 V, the positive electrode The body is characterized in that Li is contained in an amount of 1.8 to 1.4 mol with respect to 1 mol of V ₂ O ₅ 1.

In the battery of the present invention, the active material is Li, and this active material reciprocates between the negative electrode body and the positive electrode body in response to the charge / discharge operation of the battery.

First, in the negative electrode body, the atomic ratio of hydrogen / carbon (H / C) is less than 0.15; the interplanar spacing (d ₀₀₂ ) of (002) plane by X-ray wide angle diffraction method is 3.3.
7Å or more; and the crystallite size (Lc) in the C-axis direction is 150Å
Below; in the Raman spectrum analysis using an argon ion laser beam with a wavelength of 5145Å, the following formula: The G value shown by is less than 2.5;

Here, the G value means the range of fraction 1580 ± 100 cm ^{-1 in} the spectrum intensity curve recorded in the chart when Raman spectrum analysis is performed on this carbonaceous material using an argon ion laser beam with a wavelength of 5145Å. The value obtained by dividing the integral value (area intensity) of the spectrum intensity in the above by the area intensity within the range of wave number 1360 ± 100 cm ⁻¹ , and corresponds to the scale of the graphitization degree of the carbonaceous material.

That is, this carbonaceous material is an aggregate of a crystalline portion and an amorphous portion, and the G value is a parameter indicating the proportion of the crystalline portion in this carbonaceous structure.

Both of these parameters are, inter alia, H / C and d
_If both ₀₀₂ and Lc deviate from the above range,
The overvoltage at the time of charging and discharging in the negative electrode body becomes large, and as a result, gas is generated from the negative electrode body and the safety of the battery is significantly impaired. Moreover, the charge / discharge cycle characteristics are also unsatisfactory.

Furthermore, the carbonaceous material of this support has an H / C of preferably less than 0.1, more preferably less than 0.07, and particularly preferably 0.05.
Is less than.

d ₀₀₂ is preferably 3.39 to 3.75Å, more preferably 3.41 to
3.70Å; Lc is preferably 8 to 100Å, more preferably 10 to
It is 70Å.

The G value is preferably 0.1 to 2.0 or less, more preferably 0.2 to 1.5.

In addition to the above-mentioned conditions, it is preferable that the fired organic material satisfy the following conditions.

That is, the size (La) of the crystallite in the a-axis direction determined by X-ray wide-angle diffraction is preferably 10 Å or more, more preferably 15 Å or more and 150 Å or less, and particularly preferably 18 Å or more 70
Å It is less than or equal to.

Also, a distance a ₀ (= 2d ₁₁₀ ) which is twice the surface distance d ₁₁₀ of the (110) plane, which is also obtained by X-ray wide angle diffraction, is preferable.
2.38Å or more, more preferably 2.39Å or more and 2.46Å or less.

The carbonaceous material having such parameters is prepared by firing and pyrolyzing and carbonizing one or more of organic polymer compounds, condensed polycyclic hydrocarbon compounds, and polycyclic heterocyclic compounds described below. be able to. An important factor in this carbonization process is the heat treatment temperature. If the temperature is too low, carbonization will not proceed, and if it is too high, the carbonaceous state will be converted to graphite and the G value will increase. Is. The heat treatment temperature is usually set in the range of 800 to 3000 ° C., though it depends on the starting source used.

As a starting source of carbonaceous material, for example, cellulose resin; phenol resin; acrylic resin such as polyacrylonitrile and poly (α-halogenated acrylonitrile); vinyl halide resin such as polyvinyl chloride, polyvinylidene chloride and polychlorinated vinyl chloride. Polyamide imide resin;
Polyamide resin; any organic polymer compound such as polyacetylene, conjugated resin such as poly (p-phenylene); for example, naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene, naphthacene,
A condensed polycyclic hydrocarbon compound obtained by condensing two or more monocyclic hydrocarbon compounds having three or more membered rings such as picene, pyrylene, pentaphene, and pentacene, or a carboxylic acid, a carboxylic anhydride, or a carvone of the above compound. Derivatives such as acid imides, various pitches containing a mixture of the above compounds as a main component; for example, three-membered rings or more such as indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, phenatridine Heterocyclic compounds, wherein at least two or more heterocyclic compounds are bonded to each other, or are bonded to one or more monocyclic hydrocarbon compounds having three or more member rings, carboxylic acids of the above compounds, carboxylic acid anhydrides , Derivatives of carboxylic acid imides, and 1,2,4,5-tetracarboxylic acid of benzene An anhydride or its diimide; etc. can be mentioned.

The carbonaceous material prepared in this manner has an average particle size of 5
The powder is pulverized to a powder having a size of 70 μm, and a predetermined amount of a binder such as polyethylene is mixed therein, and then pelletized and formed into a sheet to form a negative electrode carrier. When this is incorporated into a battery as a negative electrode body, a treatment as described below is carried out so that a predetermined amount of Li is supported on this.

The positive electrode body of the battery of the present invention has a main component of amorphous V ₂
O ₅ . P ₂ O ₅ , WO ₃ , B ₂ O _{3 and the} like may be contained as subcomponents. These subcomponents are useful for promoting and stabilizing the amorphization of V ₂ O ₅ during the production of the positive electrode body. The content of these subcomponents is preferably in the range of 3 to 30 mol% with respect to 1 mol of V ₂ O ₅ 1. This is because when it exceeds 30 mol%, the capacity of the obtained battery is significantly reduced, and when it is less than 3 mol%, the cost is too high for amorphization and it is not industrial.

This positive electrode body was prepared by mixing the above-mentioned components in a predetermined amount, melting the mixture at a predetermined temperature, and then rapidly cooling the melt to obtain an amorphous body.
This amorphous material is pulverized and mixed with a conductive material such as carbon powder and nickel powder and a binder such as polytetrafluoroethylene, and then molded into sheets and pellets. can do.

In assembling the battery, a predetermined amount of Li is supported on the above-mentioned negative electrode body and / or positive electrode body. As a supporting method, various methods such as a chemical method, an electric chemical method, and a physical method can be applied. For example, the above-mentioned negative electrode body (or positive electrode body) in an electrolytic solution containing a predetermined concentration of Li ions can be applied. ) Is immersed, and metallic Li is used for the counter electrode, and the former is used as a cathode for electrolytic impregnation. Thus, Li ions are carried between the layers of the negative electrode body (or the positive electrode body) and in the amorphous portion.

In this case, it is supported on the negative electrode body and / or the positive electrode body.
The amount of Li ions is defined as follows.

That is, in the battery in which the negative electrode body and the positive electrode body are incorporated, when the battery voltage is 2.0 V or more (when in a charged state), the amount of Li contained in the positive electrode body is V ₂ O ₅ 1 molar amount When the battery voltage is less than 2.0 V (when discharged), the Li content in the positive electrode body is 1.8-1.4 moles relative to 1 mole of V ₂ O ₅ It is supported so that

For example, even in a completely charged state where the charging voltage of the battery is constant, it is preferable that V ₂ O ₅ of the positive electrode contains 0.4 to 0.8 mol of Li, and a completely discharged state or an overdischarged state. in, Li to the V ₂ O ₅ 1 mol of 1.8 to 1.
It is preferably contained in an amount of 4 mol.

When charged to 2.0 V or more, Li to V ₂ O ₅ 1 mol
If the amount is less than 0.4 mol, the surface deterioration of the positive electrode body will proceed, and conversely, if it is more than 0.8 mol, the battery capacity will decrease and practical problems will arise. Further, in the discharged state, when the amount of Li with respect to 1 mol of V ₂ O ₅ is less than 1.4 mol, the amount of Li transferred from the positive electrode body to the negative electrode body during charging is small and the battery capacity decreases, and conversely, it is more than 1.8 mol. This is inconvenient because it causes physical destruction of the positive electrode body during the progress of the discharge cycle or over discharge.

Li contained in the positive electrode during such charging and discharging
The amount is regulated by loading Li on the positive electrode body (or the negative electrode body) by the method described above, by calculating the amount of Li to be loaded according to their weight and volume, and then performing electrolytic impregnation treatment conditions, for example, The bath temperature, current density, and electrolysis time can be selected appropriately.

(Examples of the Invention) (1) Production of Negative Electrode Phenol resin powder was fired in N ₂ gas at 1800 ° C. for 1 hour. The resulting fired powder was crushed to an average particle size of 70
It was a powder of μm. Then, 9.4 g of this powder was mixed with 0.6 g of polyethylene powder, and 50 mg of the mixed powder was pressure-molded into pellets having a thickness of 0.5 mm.

The H / C ratio, d ₀₀₂ , Li and G values of the fired body were measured, and the results are shown in Table 1. Raman spectrum diagram 3rd
Shown as a figure.

The size and weight of the pellets are such that the amount of Li contained in the positive electrode body in the fully charged state of the assembled battery is V ₂ O ₅
It is regulated to be 0.4 to 0.8 mol per mol.

(2) Manufacture of positive electrode body V ₂ O ₅ powder 9 g, (NH ₄ ) ₃ PO ₄ 3H ₂ O particles 5.0 g (23 mol% with respect to V ₂ O ₅ ) were mixed, and the mixture was heated at 800 ° C. for 4 hours. Melted The obtained melt was poured onto a copper plate cooled with dry ice and quenched. Then, the quenched product was pulverized into a powder having an average flow diameter of 10 μm. When this powder was identified by X-ray diffraction, it was amorphous.

5 g of this amorphous powder and 0.5 g of polytetrafluoroethylene were kneaded, and the obtained kneaded product was roll-formed into a sheet having a thickness of 0.4 mm. A stainless steel net with a wire diameter of 0.1 mm and 60 mesh was pressure bonded to one surface of this sheet as a current collector to obtain a positive electrode body.

(3) Assembly of Battery The button type battery shown in FIG. 4 was assembled. That is, the positive electrode body 1 was attached to a positive electrode can 4 made of stainless steel via a current collector 7, and a polypropylene non-woven fabric was placed thereon as a separator 2, and then LiClO ₄ was added thereto at a concentration of 1
An electrolyte solution dissolved in propylene carbonate in a molar amount was injected. Then, the stainless steel negative electrode can 5 to which the negative electrode body 3 was pressure-bonded was attached thereto.

Prior to the incorporation of the positive electrode body 1, the positive electrode body was immersed in a Li electrolytic solution having a concentration of 1 mol, and this was used as a cathode for electrolytic impregnation with metallic Li as an anode. The electrolysis conditions at this time are
The bath temperature was 20 ° C, the current density was 0.5 mA / cm ² , and the electrolysis time was 15 hours.

By this treatment, the positive electrode body had a capacity of 6.0 mAh, and 1.7 mol of Li was supported per 1 mol of V ₂ O ₅ .

For comparison, a battery similar to that of the example was manufactured except that the negative electrode body was the Li foil itself, and this was used as a battery of comparative example 1.

Also, the negative electrode body is H / C0.01, d ₀₀₂ 3.39Å, Lc2.45Å, G value 5
A battery similar to that of the example was manufactured except that the fired body was the above, and this was used as a battery of comparative example 2.

Furthermore, an amount of Li is 0.2 mole in V ₂ O ₅ 1 mol of fully charged, Li amount in V ₂ O ₅ 1 mole was allowed carrying Li so that 1.2 mol complete discharge state A battery similar to that of the example was manufactured except that the positive electrode body was used, and this was used as a battery of Comparative Example 3.

(4) Characteristics of each battery Constant voltage charging −15 KΩ constant resistance discharge was repeated between 3 and 2 V for each of these batteries, and the capacity retention rate (%; initial capacity is 100) of each battery at each cycle. Was measured.
The results are shown in FIG.

Further, constant voltage charging and 15 KΩ constant resistance discharging were repeated between 3 V and 0 V, and the capacity retention rate of the battery in each cycle at that time was measured to perform deep discharge evaluation.

Furthermore, the same charge and discharge was performed between 3.6 V and 2.0 V, the capacity retention rate was measured, and overcharge evaluation was performed. The same result as in the deep discharge evaluation was obtained. The results of both are shown together in FIG.

As is clear from the figure, it was found that the battery of the present invention can be discharged regardless of overcharging and discharging, its capacity deterioration is small, and the charging / discharging cycle life is significantly extended.

[Effects of the Invention] As is clear from the above description, the non-aqueous solvent secondary battery of the present invention is not affected by overcharge and overdischarge, and has a long charge / discharge cycle life. Its high capacity, high reliability, and great industrial value.

Although the description has been given for the button type secondary battery, the present invention battery is not limited to this type and is also applicable to a non-aqueous solvent secondary battery having a shape such as a cylindrical shape, a flat shape or a prism shape. it can.

[Brief description of drawings]

1 and 2 are graphs showing the characteristics of the battery of the present invention. FIG. 3 is a chart diagram of Raman spectrum analysis of the negative electrode body of the example battery. FIG. 4 is a vertical sectional view of a non-aqueous solvent battery having a button structure. 1 ... Positive electrode body, 2 ... Separator (non-aqueous electrolyte) 3 ... Negative electrode body, 4 ... Positive electrode can 5 ... Negative electrode can, 6 ... Insulating packing 7 ... Current collector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuji Ikeda 3-4-10 Minami-Shinagawa, Shinagawa-ku, Tokyo Inside Toshiba Battery Co., Ltd. (72) Hiroyoshi Nose, 3-4-10 Minami-Shinagawa, Shinagawa-ku, Tokyo Toshiba Battery Co., Ltd. (72) Inventor Mitsutaka Miyabayashi 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. New Materials Research Laboratory (72) Inventor Akira Itsubo 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Company New Materials Research Center (72) Inventor Hiroshi Yui 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Company New Materials Research Laboratory (72) Inventor Megumi Komada 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. (56) Reference JP 60-36315 (JP, A) JP 60-182670 (JP, A) JP 61-116758 (JP, A)

Claims (1)

[Claims] 1. A hydrogen / carbon atomic ratio of less than 0.15; an interplanar spacing (d ₀₀₂ ) of (002) plane by X-ray wide angle diffraction method is 3.37 Å or more,
Crystallite size (Lc) in the C-axis direction is 150Å or less, wavelength 514
In the Raman spectrum analysis using a 5Å argon laser beam, the following formula: A non-aqueous solvent secondary battery comprising: a negative electrode body made of a fired organic material having a G value of less than 2.5; a positive electrode body mainly composed of amorphous vanadium pentoxide; and lithium as an active material. When the battery voltage is 2.0 V or higher, lithium is added to 1 mol amount of vanadium pentoxide in the positive electrode body.
When the battery voltage is less than 2.0V, the positive electrode body contains lithium in an amount of 1.8 to 1.4 moles per 1 mole of vanadium pentoxide. Solvent secondary battery.