JP2000223368A - Secondary power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high withstanding voltage, a high capacity and a superior charging-discharging cycle reliability by comprising a positive electrode, a negative electrode contg. a C material capable of occluding and desorbing Li ions, and an org. electrolyte contg. a Li salt and a specified fluorinated alkylene carbonate. SOLUTION: This secondary power source has a positive electrode contg. active C, a negative electrode contg. a C material capable of occluding and desorbing Li ions, and an org. electrolyte contg. a Li salt and fluorinated alkylene carbonate represented by formula I (m=0, 1, 2, l=0, 1, 2 where m and l will not be 0 at the same time) or II (m'=0, 1, 2, l'=0, 1, 2 where m' and l' will not be 0 at the same time) as a solvent. The concn. of the fluorinated alkylene carbonate in the used solvent of the electrolyte is set at 0.5-80 wt.% and the thickness of the negative electrode facing via the separator is 7-70% of that of the positive electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary power supply having high withstand voltage and discharge capacity and having excellent charge / discharge cycle reliability.

[0002]

2. Description of the Related Art Polarizable electrodes mainly composed of activated carbon are used for both positive and negative electrodes of conventional electric double layer capacitors. The withstand voltage of the electric double layer capacitor is 1.2 V when an aqueous electrolyte is used, and 2.5 to 3.3 V when an organic electrolyte is used. Since the energy of the electric double layer capacitor is proportional to the square of the withstand voltage, the organic electrolyte having a higher withstand voltage has higher energy than the aqueous electrolyte. However, in an electric double layer capacitor that uses an organic electrolyte and in which both the positive electrode and the negative electrode are polarizable electrodes mainly composed of activated carbon, the energy density is 1/10 or less of a secondary battery such as a lead storage battery. There is a need for improved energy density.

On the other hand, Japanese Patent Application Laid-Open No. 64-14882 discloses that an electrode mainly composed of activated carbon is used as a positive electrode and the [002] plane is 0.338 to 0.356 nm by X-ray diffraction.
There has been proposed a secondary power supply having an upper limit voltage of 3 V using an electrode in which lithium ions are previously stored in a carbon material as a negative electrode. Japanese Patent Application Laid-Open No. Hei 8-107048 proposes a secondary power source in which a carbon material which can occlude and desorb lithium ions in advance by using a carbon material in which lithium ions are occluded by a chemical method or an electrochemical method is used for a negative electrode. ing.
Further, Japanese Patent Application Laid-Open No. 9-55342 proposes a secondary power supply having an upper limit voltage of 4 V, having a negative electrode in which a carbon material capable of absorbing and desorbing lithium ions is supported on a porous metal current collector that does not form an alloy with lithium. Have been.

A secondary power supply using activated carbon for the positive electrode and a carbon material capable of occluding and releasing lithium ions for the negative electrode has a higher voltage than conventional electric double layer capacitors using activated carbon for both the positive electrode and the negative electrode. In addition, the capacity can be increased. In particular, when a graphite-based carbon material having a low lithium ion occlusion / desorption potential is used for the negative electrode in the secondary power supply, the capacity can be further increased.

[0005] However, in the case of a graphite-based carbon material used for the negative electrode, lithium ions cannot be inserted or extracted unless an electrolyte containing 1,3-dioxolan-2-one (ethylene carbonate) as a main solvent is used. However, the electrolyte using 1,3-dioxolan-2-one as a solvent has a problem that the stability at a high temperature is insufficient for a positive electrode using activated carbon.

A secondary power supply capable of charging and discharging a large current includes a lithium ion secondary battery in addition to an electric double layer capacitor and a secondary power supply. Although it has the properties of high voltage and high capacity, it has a problem that the resistance is high and the life due to the rapid charge / discharge cycle is significantly shorter than that of the electric double layer capacitor.

[0007]

SUMMARY OF THE INVENTION The present invention provides an electrolytic solution containing an electrochemically stable solvent, for example, with respect to activated carbon of a positive electrode and a carbon material capable of inserting and extracting lithium ions of an anode. It is an object of the present invention to provide a secondary power supply capable of rapid charge and discharge, high withstand voltage, high capacity, high energy density, and high charge / discharge cycle reliability.

[0008]

According to the present invention, a positive electrode, a negative electrode containing a carbon material capable of occluding and releasing lithium ions, a lithium salt and a compound represented by the formula (1)
(2) An organic electrolytic solution containing a fluorinated alkylene carbonate represented by the following formula (7):

[0009]

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[0010]

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Further, according to the present invention, a lithium salt and a compound represented by the formula
(1) comprising a fluorinated alkylene carbonate represented by the following formula (2) or (2):
Provided is an organic electrolyte suitably used for a secondary power supply, comprising: a negative electrode containing a carbon material capable of inserting and extracting lithium ions.

[0012]

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[0013]

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[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a negative electrode body is defined by joining and integrating a negative electrode mainly composed of a carbon material capable of occluding and releasing lithium ions and a current collector.
The negative electrode body forms a non-polarizable electrode. On the other hand, the positive electrode body forms a polarizable electrode, and is preferably formed by bonding a current collector to a positive electrode containing activated carbon similarly.

In a broad sense, both the secondary battery and the electric double layer capacitor are a kind of secondary power supply.
A secondary power supply having a specific configuration in which the positive electrode preferably contains activated carbon and the negative electrode contains a carbon material capable of inserting and extracting lithium ions will be simply referred to as a secondary power supply.

The present invention basically relates to a secondary power supply having a positive electrode preferably containing activated carbon, a negative electrode containing a carbon material capable of absorbing and desorbing lithium ions, and an organic electrolyte containing a lithium salt. And a fluorinated alkylene carbonate having a high decomposition voltage represented by the formula (1) or (2) is contained as a solvent for the organic electrolytic solution.

Such fluorinated alkylene carbonates include 4-fluoro-1,3-dioxolan-2-
ON, 4,4-difluoro-1,3-dioxolan-2-
On, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4,4,5,5-tetrafluoro-1,3-
Fluorinated ethylene carbonates such as dioxolan-2-one; 4-methyl-4-fluoro-1,3-dioxolan-2-one, 4-methyl-4,5 difluoro-1,3-dioxolan-2-one, -Methyl-5-fluoro-1,
3-dioxolan-2-one, 4-methyl-5,5-difluoro-1,3-dioxolan-2-one, 4-methyl-4,5,5-trifluoro-1,3-dioxolan-2
And fluorinated propylene carbonate such as -one. Most preferred among these is 4-fluoro-1,3-dioxolan-2-one, which is a monofluorinated ethylene carbonate. In addition, 1 to 3 methyl groups at the 4-position may be further fluorinated.

In the present invention, at least one kind of the above fluorinated alkylene carbonate is used as a solvent for the electrolytic solution.
On, 4-methyl-1,3-dioxolan-2-one,
4-ethyl-1,3-dioxolan-2-one, 4,5
Cyclic alkylene carbonates such as -dimethyl-1,3-dioxolan-2-one; linear alkyl carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; sulfolane (tetramethylsulfone), 1,2-dimethoxyethane, dimethylsulfoxide , N, N-dimethylformamide and γ-butyrolactone can be used as a mixed solvent with one or more solvents selected from the group consisting of:

The concentration of the fluorinated alkylene carbonate in the solvent used in the electrolytic solution is 0.5 to 80% by weight, preferably 10 to 80% by weight, more preferably 20 to 80% by weight, and further preferably 30 to 80% by weight. % Or more.
When the amount is less than 0.5% by weight, the effect of including the fluorinated alkylene carbonate in the organic electrolyte is small, and when the amount exceeds 80% by weight, the conductivity of the electrolyte decreases significantly when the use temperature decreases.

Examples of the carbon material capable of occluding and releasing lithium ions of the negative electrode according to the present invention include a graphite-based carbon material, a low-temperature calcined carbon material, and hard carbon, and the like. Preferred are graphite-based carbon materials.

In the present invention, the formula (1) or (2)
By using one kind of the fluorinated alkylene carbonate specified in the above as a solvent, the oxidative decomposition voltage of the solvent can be increased without sacrificing other characteristics, and the oxidative decomposition potential of the secondary power source is increased. is there.

More specifically, this effect is achieved by converting fluorinated alkylene carbonate to 1,3-dioxolane-2.
When used in combination with -on, the stability to voltage application at a high temperature to the positive electrode containing activated carbon is improved as compared with the case of using only 1,3-dioxolan-2-one,
And occlude lithium ions in the graphite-based carbon material of the negative electrode,
The reversible capacity at the time of desorption can be increased.

When a solvent obtained by adding a fluorinated alkylene carbonate to 4-methyl-1,3-dioxolan-2-one is used as an electrolytic solution, even when a graphite-based carbon material is used for the negative electrode, the amount of 4 -Methyl-1,3-
Electrolysis of dioxolan-2-one is suppressed, and occlusion and desorption of lithium ions are performed efficiently.

Incidentally, 4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2 -One, 4,4,5,5-tetrafluoro-
So-called fluorinated ethylene carbonate such as 1,3-dioxolan-2-one is also stable to a positive electrode containing activated carbon.

As described above, conventionally, when an electrolyte containing 1,3-dioxolan-2-one as a main solvent is used for a negative electrode containing a graphite-based material, lithium ions can be efficiently absorbed and desorbed. However, this electrolyte was insufficient in stability at a high temperature voltage application with respect to the positive electrode containing activated carbon.

On the other hand, 4-methyl-1,3-dioxolan-2-one is stable when a voltage is applied to a positive electrode containing activated carbon, but uses 4-methyl-1,3-dioxolan-2-one as a main solvent. In an electrolyte containing a lithium salt, it has been difficult to cause the graphite-based material to occlude lithium ions. This is because the potential with respect to the lithium reference electrode is approximately equal to the case where the graphite material is made to occlude lithium ions by an electrochemical method, and the solution is made to absorb lithium ions by facing the positive electrode using the solution as an electrolytic solution and charging. This is because electrolysis of 4-methyl-1,3-dioxolan-2-one occurs around 0.8V.

These problems can be suitably solved by using the electrolytic solution containing the fluorinated alkylene carbonate of the present invention. When fluorinated ethylene carbonate is used, its melting point is lower than that of ethylene carbonate [for example, the melting point (17 ° C.) of 4-fluoro-1,3-dioxolan-2-one is 1,3. −20 ° C. lower than the melting point (39 ° C.) of dioxolan-2-one], but can be used at low temperatures, but mixed with a low-viscosity linear alkyl carbonate such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc. It is preferable to use it because it can be used at a lower temperature. In this sense, it is also a preferable embodiment to use the fluorinated ethylene carbonate in a mixture with 4-methyl-1,3-dioxolan-2-one.

In the secondary power supply of the present invention, the anions in the electrolyte are adsorbed to the activated carbon or the like of the positive electrode by charging, and the lithium ions in the electrolyte are stored in a carbon material capable of absorbing and desorbing the lithium ions of the negative electrode. You. Then, lithium ions are desorbed from the negative electrode by discharge, and anions are desorbed from the positive electrode.
That is, in the secondary power supply of the present invention, the solute of the electrolytic solution is essentially involved in charge and discharge.

On the other hand, in a lithium ion secondary battery, the positive electrode is usually made of an electrode mainly composed of a lithium-containing transition metal oxide such as LiCoO ₂ or LiMn ₂ O ₄ , and the negative electrode is made of carbon that can occlude and desorb lithium ions. It is an electrode mainly composed of a material. Lithium ions are desorbed from the lithium-containing transition metal oxide, which is a positive electrode active material, by charge, and occluded in a carbon material capable of occluding and desorbing lithium ions on the negative electrode. Is occluded. That is, since lithium ions are absorbed and desorbed into and from the positive electrode active material itself, the positive electrode active material is significantly deteriorated due to charge / discharge cycles.

As described above, in the secondary power supply of the present invention, the charging / discharging mechanism is different from that of the lithium ion secondary battery, and lithium ions are occluded in the positive electrode active material itself as in the lithium ion secondary battery. And does not desorb, and there is no deterioration of the positive electrode due to occlusion and desorption of lithium ions. For this reason, the secondary power supply of the present invention has an operation and effect that the deterioration due to the charge / discharge cycle is small and the long-term reliability is excellent.

In the present invention, the carbon material of the negative electrode includes:
Lithium ions may be stored in advance by a chemical method or an electrochemical method.

As a chemical method, for example, while the negative electrode carbon material is in contact with lithium metal, it is immersed in an electrolytic solution or another organic solvent in which a lithium salt is dissolved, and heated to ionize lithium to form a negative electrode. A method in which the carbon material is occluded, or a method in which powdery lithium metal is mixed with a carbon material which can be occluded or released while lithium ions are ionized, can be adopted. On the other hand, electrochemical methods include
For example, a method in which a negative electrode carbon material and a lithium metal are opposed via a separator, the negative electrode carbon material is charged at a constant current or a constant voltage in an electrolytic solution, and lithium ions are incorporated into the carbon material in a state of being ionized can be adopted.

In the secondary power supply of the present invention, if the positive electrode capacity and the negative electrode capacity are formed so as to be substantially equal, lithium ions are previously absorbed into the carbon material of the negative electrode by the chemical method or the electrochemical method as described above. Even without this, the potential of the negative electrode can be made sufficiently low only by charging the secondary power supply. Usually, since the negative electrode capacity is larger than the positive electrode capacity, it is possible to make the positive electrode capacity and the negative electrode capacity substantially equal by molding the negative electrode containing the carbon material so that the thickness of the negative electrode is smaller than the thickness of the positive electrode. is there.

On the other hand, when the thickness of the positive electrode and the thickness of the negative electrode are substantially the same, the negative electrode capacity is larger than the positive electrode capacity. Therefore, the potential of the negative electrode does not become sufficiently low when charging the secondary power supply. It does not become a high-voltage secondary power supply without absorbing ozone. Specifically, the thickness of the negative electrode opposed to the thickness of the positive electrode via the separator is 3 to 80%, particularly 7 to 70%, further 10 to 60%, and further 15 to 4%.
It is preferably 0%. When the thickness ratio between the positive electrode and the negative electrode is in this range, the capacity of the positive electrode and the capacity of the negative electrode are balanced as described above, and a secondary power supply with high withstand voltage can be configured.

The thickness of the positive electrode is 80 to 250 μm, particularly 10
It is preferably from 0 to 220 μm. If the thickness is less than 80 μm, the capacity of the secondary power supply cannot be sufficiently increased.
If it exceeds m, the resistance increases during charging and discharging, and is not practical for rapid charging and discharging.

On the other hand, the thickness of the negative electrode is specifically 10 to 1
50 μm is preferred. A negative electrode having a thickness of less than 10 μm is difficult to form. Particularly preferably, the thickness of the positive electrode is 1
And the thickness of the negative electrode is 15 to 5 μm.
0 μm.

In the secondary power supply of the present invention, the positive electrode and the negative electrode may be formed on one side or both sides of the current collector. Even when formed on both sides, it means the thickness of the electrode layer formed on one side of the current collector.

The current collector may be any conductor that is electrochemically or chemically resistant to corrosion. Examples of the current collector used for the positive electrode include stainless steel, aluminum, titanium, and tantalum. Examples of the current collector include stainless steel, copper, and nickel that do not react with lithium.

In the present invention, the activated carbon contained in the positive electrode preferably has a specific surface area of 800 to 3000 m ² / g. Activated carbon raw materials and activation conditions are not limited,
For example, as raw materials, coconut, phenolic resin, petroleum coke, and the like can be mentioned. As the activation method, a steam activation method,
A molten alkali activation method and the like can be mentioned. Activated carbon obtained by activating steam from coconut or phenolic resin is particularly preferred.

In order to reduce the resistance of the positive electrode, it is also a preferred embodiment to include conductive carbon black or graphite as a conductive material in the positive electrode. Preferably, it is contained at 20% by weight.

As a method for producing a positive electrode body, for example, a mixture of activated carbon powder and a conductive material is mixed with polytetrafluoroethylene as a binder, kneaded and then formed into a sheet to form a positive electrode, which is used as a current collector. There is a method of fixing using a conductive adhesive. Further, polyvinylidene fluoride, polyamide imide, polyimide and the like as a binder,
There is a method in which activated carbon powder and conductive material powder are dispersed in a varnish obtained by dissolving this in an organic solvent, and this liquid is coated on a current collector by a doctor blade method or the like, and dried. The amount of the binder contained in the positive electrode is 1 to 20% by weight based on the balance between the strength of the positive electrode body and characteristics such as capacity.
It is preferred that

In the present invention, the carbon material capable of inserting and extracting lithium ions in the negative electrode preferably has a [002] plane spacing of 0.335 to 0.410 nm as determined by X-ray diffraction. If it is in this range, natural graphite as a carbon material capable of occluding and desorbing lithium ions,
Heat treatment temperature of artificial graphite, petroleum coke, mesophase pitch-based carbon material or vapor grown carbon fiber is 800 to 300
Any of materials changed between 0 ° C. and non-graphitizable carbon materials can be suitably used. Among them, when used particularly for a secondary power supply, a graphite-based carbon material having a [002] plane spacing of 0.335 to 0.338 nm is preferable from the viewpoint of low resistance. If the surface spacing is much larger than this, the deterioration is remarkable in the charge / discharge cycle, which is not preferable.

Specific examples of the graphite-based carbon material include mesophase pitch-based carbon fibers, mesocarbon microbeads, carbon materials obtained by heat-treating a vapor-grown carbon material at 2800 ° C. or higher, and natural graphite.

On the other hand, similarly to the positive electrode, the negative electrode body of the present invention is kneaded with polytetrafluoroethylene as a binder, formed into a sheet, formed into a negative electrode, and adhered to the current collector using a conductive adhesive. Let me get it. Also,
Polyvinylidene fluoride, polyamide imide or polyimide and the like as a binder, the carbon material is dispersed in a solution in which a resin serving as a binder or a precursor thereof is dissolved in an organic solvent, applied to a current collector by a doctor blade or the like, and dried. There is also a way to get it. All of these methods are preferred.

In the method of obtaining the negative electrode body by applying the above solution to the current collector, the solvent for dissolving the resin serving as the binder or the precursor thereof is not particularly limited, but the resin constituting the binder or the precursor thereof is easily prepared. In N-methyl-2-pyrrolidone (hereinafter referred to as N-methyl-2-pyrrolidone).
MP) is preferred. Here, the precursor of polyvinylidene fluoride, the precursor of polyamideimide, or the precursor of polyimide refers to those which are polymerized by heating to be polyvinylidene fluoride, polyamideimide, or polyimide, respectively. Other solvents include dimethylformamide, toluene, xylene, methyl ethyl ketone,
Methyl isobutyl ketone, ethyl acetate and the like can be used.

The binder obtained as described above is cured by heating to form an electrode body having excellent chemical resistance, mechanical properties and dimensional stability. The temperature of the heat treatment is preferably 200 ° C. or higher. 200 ° C
If it is the above, even if it is a precursor of a polyamideimide or a precursor of a polyimide, it usually polymerizes and becomes a polyamideimide or a polyimide, respectively. The atmosphere for the heat treatment is preferably an inert atmosphere such as nitrogen or argon or a reduced pressure of 1 torr or less. Instead of heat treatment, a technique of curing by irradiation with UV light may be adopted. Polyamide imide or polyimide is resistant to the organic electrolyte used in the present invention, and is used to remove water from the negative electrode.
It is sufficiently resistant to high-temperature heating of about ° C or heating under reduced pressure.

In the present invention, when the negative electrode and the current collector are joined to form a negative electrode body, if an adhesive layer made of polyamideimide or polyimide is interposed between the negative electrode and the current collector, the negative electrode and the current collector are bonded. The power becomes stronger. In this case, a varnish obtained by previously dissolving polyamideimide, polyimide or their precursors in a solvent on a current collector is applied by a coating method such as a doctor blade method, and dried to form an adhesive layer. It is preferable to form a negative electrode. Alternatively, it is also preferable that the negative electrode is laminated before the applied film is dried or in a semi-dry state, and then dried and polymerized and cured in this state.

When the adhesive layer is formed, it is preferable to disperse a conductive material such as copper powder, silver powder, and graphite powder in the varnish because the contact resistance between the negative electrode and the current collector can be reduced. The varnish containing the conductive material may be interposed as a conductive adhesive between the activated carbon layer and the current collector when the layer containing activated carbon is formed into a sheet.

In the present invention, the weight ratio of the carbon material capable of occluding and releasing lithium ions and the binder in the negative electrode is preferably 70:30 to 96: 4. When the amount of the binder is more than 30% by weight, the capacity of the negative electrode becomes small. On the other hand, if the amount of the binder is less than 4% by weight, the effect as a binder is weakened, and the separation between the negative electrode and the current collector is increased.

The lithium salt contained in the organic electrolyte according to the present invention includes LiPF ₆ , LiBF ₄ , LiClO ₄ , L
iN (SO ₂ CF ₃ ) ₂ , LiB (C ₆ H ₅ ) ₄ , Li
C ₄ F ₉ SO ₃ , LiC ₈ F ₁₇ SO ₃ , LiB (C ₆ F ₅
) ₄ , CF ₃ SO ₃ Li, LiC (SO ₂ CF ₃ )
₃ , one or more selected from the group consisting of LiAsF ₆ and LiSbF ₆ is preferred. The concentration of the lithium salt in the electrolytic solution is 0.1 to 2.5 mol / L, and more preferably 0.5 to 2.5 mol / L.
2 mol / L is preferred.

[0051]

EXAMPLES Next, Examples (Examples 1 to 3) and Comparative Examples (Examples 4 to 5)
The present invention will be described more specifically with reference to 5), but the present invention is not limited thereto. The production and measurement of the cells of Examples 1 to 5 were all performed in an argon glove box having a dew point of −60 ° C. or less.

Example 1 (1) Formation of Positive Electrode Body 80% by weight of activated carbon having a specific surface area of 2,000 m ² / g, 10% by weight of conductive carbon black obtained by a steam activation method using a phenol resin as a raw material, and poly as a binder A mixture consisting of 10% by weight of tetrafluoroethylene was kneaded with ethanol, rolled, and then vacuum dried at 200 ° C. for 2 hours to obtain an electrode sheet having a thickness of 150 μm. An electrode of 1 cm x 1 cm was obtained from this electrode sheet,
It is bonded to an aluminum foil as a current collector using a conductive adhesive having polyamideimide as a binder.
Heat treatment was performed at 00 ° C. for 10 hours to obtain a positive electrode body.

(2) Formation of Negative Electrode Body Next, a graphite-based carbon material having a [002] plane spacing of 0.338 nm was used as a carbon material capable of inserting and extracting lithium ions, and polyamideimide was dissolved in NMP. The resultant was dispersed in a solution, applied to a current collector made of copper, and dried to form a negative electrode on the current collector. The weight ratio of the carbon material capable of occluding and releasing lithium ions in the negative electrode and the polyamideimide was 9: 1. This was further pressed with a roll press machine to make the area of the negative electrode 1 cm × 1 cm and the thickness 15 μm, and heat-treated at 260 ° C. for 10 hours under reduced pressure to obtain a negative electrode body.

(3) Formation of Element An element was produced by sandwiching the positive electrode body and the negative electrode body with their electrode surfaces facing each other via a polypropylene separator and sandwiching them with a sandwiching plate. Propylene carbonate and 4-
Using a mixed solvent having a weight ratio of 4: 1 to fluoro-1,3-dioxolan-2-one, LiBF ₄ was added at 1 mol /
A solution dissolved at a concentration of L was used as an electrolytic solution, the element was sufficiently impregnated, and the initial capacity was measured in a range from 4.2 V to 3 V. Then, at a charge / discharge current of 10 mA / cm ² ,
The charge / discharge cycle was performed in the range of 4.0 V to 2.75 V, the capacity after 2000 cycles was measured, and the rate of change of the capacity was calculated. Table 1 shows the results.

Example 2 Propylene carbonate and 4-fluoro-1,3-dioxolan-2-one (weight ratio 4:
A secondary power source was prepared in the same manner as in Example 1 except that a mixed solvent of 4-fluoro-1,3-dioxolan-2-one and ethyl methyl carbonate (weight ratio 1: 1) was used instead of the mixed solvent of 1). Was obtained and evaluated in the same manner as in Example 1. Table 1 shows the results.

[Example 3] An example except that a mixed solvent of propylene carbonate and 4-fluoro-1,3-dioxolan-2-one having a weight ratio of 20: 1 instead of 4: 1 was used. A secondary power source was obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 4 Weight ratio of propylene carbonate to 4-fluoro-1,3-dioxolan-2-one 4:
A secondary power source was obtained in the same manner as in Example 1 except that only propylene carbonate was used as the solvent instead of 1, and the evaluation was performed in the same manner as in Example 1. Table 1 shows the results.

[Example 5] Instead of a mixed solvent of 4-fluoro-1,3-dioxolan-2-one and ethyl methyl carbonate (weight ratio 1: 1), ethylene carbonate and ethyl methyl carbonate (weight ratio 1: A secondary power source was obtained in the same manner as in Example 2 except that the mixed solvent of 1) was used.
Was evaluated in the same way as Table 1 shows the results.

[0059]

[Table 1]

[0060]

According to the present invention, since an electrolyte containing a fluorinated alkylene carbonate that is stable for both the positive electrode and the negative electrode in the charge / discharge cycle is used, the withstand voltage is high, the capacity is large, and rapid charging is performed. It is possible to provide a secondary power supply with high discharge cycle reliability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/40 H01G 9/00 301A (72) Inventor Go Morimoto 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass (72) Inventor Manabu Tsushima 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture F-term in Asahi Glass Co., Ltd. (Reference) AK08 AL06 AL07 AM03 AM04 AM05 AM07 DJ16 DJ17 EJ11 HJ00 HJ04 HJ13

Claims (8)

[Claims] 1. A positive electrode, a negative electrode containing a carbon material capable of inserting and extracting lithium ions, a lithium salt and a compound represented by the formula (1):
A secondary power source comprising: an organic electrolyte containing a fluorinated alkylene carbonate represented by the following formula (1) or (2). Embedded image Embedded image 2. The method according to claim 1, wherein the positive electrode contains activated carbon.
The described secondary power supply. 3. The fluorinated alkylene carbonate of the formula
(3) The secondary power source according to claim 1 or 2, which is 4-fluoro-1,3-dioxolan-2-one represented by the following formula (3). Embedded image 4. The electrolytic solution according to claim 1, wherein the concentration of the fluorinated alkylene carbonate is 0.5 to 80% by weight.
The secondary power supply according to any one of the above. 5. The carbon material has a [002] plane spacing of 0.335 to 0.410 nm.
The secondary power supply according to any one of the above. 6. The secondary power source according to claim 1, wherein lithium ions are previously stored in the carbon material by a chemical method or an electrochemical method. 7. The secondary power supply according to claim 1, wherein the thickness of the negative electrode containing the carbon material is 7 to 70% of the thickness of the positive electrode. 8. A carbon material comprising a lithium salt and a fluorinated alkylene carbonate represented by the formula (1) or (2) or (2), capable of occluding and releasing lithium ions. An organic electrolyte suitably used for a secondary power supply having a negative electrode containing: Embedded image Embedded image