JPS6376274A - Secondary battery - Google Patents

Abstract

PURPOSE:To obtain a high performance secondary battery having large enrgy density, good charge-discharge reversibility, low self-discharge rate, and long cycle life by adding a specified amount of alkali metal fluoride in an electrolyte comprising alkali metal salt and nonaqueous solvent. CONSTITUTION:In a secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte, the negative electrode consists of an alkali metal alloy or a composite of the alkali metal alloy and a conductive polymer, and the electrolyte consists of alkali metal salt containing fluorine indicated in the formula M.XFn (M is an alkali metal, X is an element selected from a group of B, P, As, Sb, and Si, n is an integer of 4-6) and a nonaqueous solvent, and the concentration of alkali metal fluoride indicated in the formula MF (M is an alkali metal) is 0.001-2 wt% of the nonaqueous solvent. By specifying the concentration of the alkali metal fluoride to 0.001-2 wt%, the high performance battery having large energy density, high charge-discharge efficiency, and long cycle life can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a high-performance secondary battery that has high energy density, good charge/discharge reversibility, extremely low self-discharge rate, and long cycle life. Regarding the next battery.

[Prior Art] In recent years, secondary batteries using lithium as a negative electrode have been actively developed.

When lithium is used in the electrode, it is necessary to use a non-aqueous electrolyte because of the high reactivity between water and lithium.

However, when lithium is used as a negative electrode active material, since lithium has a very high activity, there are problems such as dendrites generated during charging, resulting in a decrease in charging and discharging efficiency and short-circuiting of the positive and negative electrodes.

Therefore, it prevents dendrites and improves the charging and discharging efficiency of the negative electrode.
Many technological developments have been reported to improve cycle life.1 For example, a method using a methylated cyclic ether solvent as a battery electrolyte medium [KM Abraham et al.・Edited by P. Gavano9, published by Academic Press, London (
(1983) (K.H.Abraham et a.
l, in”Lithium Batteries
”, J. P. Gabano, editor.

Academic press, London (1
983) > ) and ff1ffi itself is alloyed with aluminum to prevent lithium andrite (B, M, L, Rao, R, W, Francis and H, Nie, Christopher, Journal of Electron. chemical society,
Volume 124, No. 10, pp. 1490-1492,
(1977) (8, M, L, Rao, R, W, F
rancis, and H.A., Christopher
r, J, Electrochel, Soc.

Vol, 124. No, 10.1490-1492
(1977) ) etc. have been proposed.

On the other hand, it is known that a conductive polymer is used as the positive electrode active material, and it is also known that a material that forms an intercalation compound with an alkali metal such as TiS2, or other chalcogenide compounds or inorganic oxides is used. It is being

Conductive polymers used as positive electrode active materials include polyacetylene, polythiophene, polythiophene derivatives, polyvaraphenylene, and polyvaraphenylene I.
There are s-forms, polypyrrole, polypyrrole derivatives, and other aniline-based polymers such as polyaniline and polyaniline derivatives are well known. Further, as specific examples of chalcogenide compounds and II-free compounds used as positive electrode active materials, 20. Including, Nb5S4゜Mo
3S4. Co S2. Fe82, Ti32.

Cr2o5. Mn 02 , Si 02 , Co 02
゜SnO2 and the like are known.

[Problems to be solved by the invention] However, when a secondary battery is constructed using an alkali metal alloy for the negative electrode and an aniline polymer for the positive electrode, it is difficult to achieve sufficient reversibility and a low self-discharge rate at the same time. It has been difficult to obtain a secondary battery with a satisfactory high energy density.

This difficulty is largely due to the fact that a stable electrolytic solution with a high ionic conductivity sufficient to reversibly charge and discharge a battery having a large electromotive force of 3 V or more has not been found. For example, a mixed solvent such as propylene carbonate and 1,2-dimethoxyethane, which are commonly used in non-aqueous lithium batteries, may be mixed with Li B F 4 or L
The electrolytic solution containing iCNO4 has high current efficiency because the solvent decomposes during battery operation (charging or discharging), forming a high-resistance film on the negative electrode surface, and increasing the internal pressure of the battery due to decomposition gas, etc. cannot be repeatedly charged and discharged. In particular, if a high-resistance film forms on the surface of the negative electrode, that part will be damaged.
The battery becomes i7I, and current concentrates locally in areas where electricity can easily pass, causing dendrite formation and electrode collapse, and the overvoltage rapidly increases, making it impossible to operate as a battery.

As a result of intensive research to solve the above problems, the present inventors have discovered that high-performance secondary It was discovered that a battery can be obtained.

The present invention has been made based on the above-mentioned findings, and eliminates the drawbacks of the conventional technology. The purpose is to provide secondary batteries.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and its gist is that in a secondary battery consisting of a positive electrode, a negative electrode, and a non-aqueous electrolyte, the negative electrode is made of alkaline earth metal. , or a composite of an alkali metal alloy and a conductive polymer, and the electrolyte of the electrolyte has the following general formula [M is an alkali metal, X is B, P, Δs, 3b
.

Si, an element selected from the group consisting of; n represents an integer of 4 to 6; ] It consists of a fluorine-containing alkali metal salt represented by the following and a nonaqueous solvent, and is represented by the following general formula MF (M represents an alkali metal).

The concentration of alkali metal fluoride is 0 compared to nonaqueous solvents.
．． 001-2% in secondary batteries.

[Specific structure and operation of the invention] The present invention will be explained in detail below.

In the present invention, the alkali metal alloy used as the negative electrode is an alloy of an alkali metal and at least one type of metal selected from nY consisting of aluminum, magnesium, manganese, tin, zinc, bismuth, silicon, lead, and cadmium. , typical examples include Li/AfJ alloy, Li
/MCI alloy, Li/Aρ/M (1 alloy, Li /Si
alloy, Li/11/Si alloy, etc. In this case, the alloy ratio is not particularly limited, but it is preferable that the alkali metal atomic ratio during charging is 20% or more.

In addition, the composites used as the negative electrode in the present invention include the alkali metal alloy and polypyrrole, polypyrrole derivatives, polythiophene, polythiophene derivatives,
Examples include a complex with at least one conductive polymer selected from the group consisting of polyquinoline, boriacene, polyparaphenylene, and polyacetylene. Typical examples of composites include a composite of Li/A1 alloy and polyparaphenylene, a composite of Li/A, Q alloy and polyacetylene,
Examples include a composite of Li/Mg alloy and polyparaphenylene. The term "composite" as used herein refers to a homogeneous mixture of an alkali metal alloy and a conductive polymer, a laminate, or a modified product in which a base component is modified with another component.

In the present invention, an inorganic oxide, a calgeconide compound, a conductive polymer, etc. can be used for the positive electrode, and among the conductive polymers, an aniline polymer is preferable. This aniline polymer is an oxidized polymer of an aniline compound represented by the following general formula (1).

[In the formula, R1-R4 may be different or the same,
Hydrogen atom, alkyl group having 1 to 10 carbon atoms, 1 carbon number
-10 alkoxy group or aryl group having 6 to 10 carbon atoms. ] Typical examples of aniline compounds represented by the above general formula include aniline, 2-methoxy-aniline, 3-methoxy-aniline, 2,3-dimethoxy-aniline, 2.5-
Dimethoxy-aniline, 2,6-simethoxyaniline, 3,5-dimethoxy-aniline, 2-ethoxy-3-
Methoxy-aniline, 2,5-diphenylaniline, 2
-Phenyl-3-methyl-aniline, 2.3.5-trimethoxy-aniline, 2,3-diferaniline, 2,
Examples include 3,5,6-titramethyl-aniline, among which aniline is most preferred.

Electrochemical polymerization methods and chemical polymerization methods are known as methods for producing aniline polymers. An example of a known document on the electrochemical polymerization method is the Journal of the Chemical Society of Japan, Tori 1.
1.1801 pages (1984) is known, and examples of known literature on chemical polymerization methods include A.G. Green and A.E. Woodhead, Journal of the Chemical Society; , page 2388,
1910 (A, G, Green and^, E, Wo
odhead, J., Chem, Soc.

2388 (1910)) is known, but aniline polymers are generally produced by the following method.

In the case of the electrochemical polymerization method, the polymerization of the aniline compound is performed by anodic oxidation, and the polymerization rate is about 0.01 to 50 mA/cm.
2. The electrolytic voltage is usually in the range of 1 to 10 V, and a constant current method, a constant voltage method, and any other method can be used. The polymerization is carried out in an aqueous solution or a nonaqueous solvent, such as an alcohol, a nitrile, or a mixed solvent thereof, but preferably in an aqueous solution. The non-aqueous solvent may or may not dissolve the produced aniline polymer (oxidized polymer).

There is no particular restriction on the pH of the electrolytic solution, but it is preferable that the pH of the electrolyte be
tl is 4 or less, particularly preferably pH is 2 or less. p
Specific examples of acids used to adjust tl include HCj, H
Examples include BF, CF3COOH, H2S4 and HNO3, but are not particularly limited to these.

In the case of chemical polymerization, for example, aniline compounds can be oxidatively polymerized in an aqueous solution with a strong oxidizing acid or with a combination of a strong acid and a peroxide, such as potassium pertarate. The aniline polymer (oxidized polymer) obtained by this method can be obtained in powder form, so
This can be separated and dried before use.

In addition, in both the electrochemical polymerization method and the chemical polymerization method, other additives such as carbon black, polytetrafluoroethylene powder, polyethylene glycol, polyethylene oxide, etc. are added to the polymerization electrolyte. Polymerization is also possible.

The non-aqueous solvent for the electrolyte used in the secondary battery of the present invention includes:
Those that are aprotic and have a high dielectric constant are preferred. For example, ethers, ketones, sulfur compounds, phosphate ester compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds, sulfolanes, etc. can be used, but among these, ethers, ketones phosphoric acid ester compounds, chlorinated hydrocarbons, carbonates, and sulfolanes are preferable, and it is particularly preferable to use a combination of ethers and carbonates.

Representative examples of these nonaqueous solvents include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, monoglyme, 4-methyl-2-pentanone, 1,2-
Dichloroethane, γ-butyrolactone, valerolactone, dimethoxyethane, methylformate, propylene carbonate, ethylene carbonate, dimethylformamide, dimedyl sulfoxide, dimethylthioformamide, ethyl phosphate, methyl phosphate, chlorobenzene,
Examples include sulfolane and 3-methylsulfolane. Two or more of these solvents may be used in combination.

Further, as a specific example of the alkali metal salt whose anion is a fluoride used in the secondary battery of the present invention, Li PF
6. LiSbF6. KPF6.

Examples include Na PF , LiBF , LiAs F6, etc., but the anion is not necessarily limited to these, as long as the anion is a fluorine-containing alkali metal salt. These alkali metal salts may be used alone or in combination of two or more.

The concentration of the alkali metal salt varies depending on the charging conditions, operating temperature, type of alkali metal salt, type of non-aqueous solvent, etc., so it cannot be specified unconditionally, but it is generally 0.5.
It is preferably within the range of ~10 mol/ρ. The electrolyte may be homogeneous or heterogeneous.

In the present invention, an alkali metal fluoride is added to the electrolyte. As an alkali metal fluoride, L
Examples include iF, KF, NaF, etc.

The amount of the alkali metal fluoride added is 0.001 to 2%, preferably 0.01 to 0.5%, based on the weight of 81 degrees with respect to the nonaqueous solvent in the electrolytic solution. The amount added is 0.0 in Chongyang Yuan degree.
If the amount is less than 0.01%, the effect of the present invention cannot be obtained;
If it is more than 2% at 1 degree fH, adverse effects such as a decrease in electrical conductivity will be strong, and both charging and discharging efficiency and reversibility will decrease.

In the secondary battery of the present invention, the amount of dopant doped into the aniline polymer of the positive electrode is 10 to 100 mol%, preferably 20 to 100 mol%, per 1 mol of repeating units of the aniline polymer. %.

The amount of doping can be freely controlled by measuring the electricity m flowing during electrolysis.

Doping may be performed under constant current, constant voltage, or varying current and voltage conditions.

In addition, in the secondary battery of the present invention, a preferable value of alkali gold FAm (
(discharge depth) is 2% relative to the alkali gold Effi in the alloy.
~90%.

However, if the discharge depth is too large, the electrodes tend to deteriorate, and if the discharge depth is too small, the energy density of the entire battery will decrease. It is desirable to set the depth.

In the present invention, the effect of adding alkali metal fluoride to the electrolyte is extremely significant, and its mechanism of action is as follows:
Although it is not clear, PF5°Sb F , BF3. As
F5 etc. reacts with alkali metal fluoride to produce P.
F-, Sb F6-.

Returning to BF +, As F6-, etc., it is considered that anions are always effectively used.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 (Production of polyaniline) A platinum plate (15 mφ, diameter 0.5 my
With a lead wire of φ), a constant current density LOmA/
Electrolytic polymerization was performed using ctx2. In this case, a platinum plate with the same diameter as above was used as the counter electrode, and an AO/AgCJI electrode was used as the reference electrode.

When the polymerization was stopped when the electrolytic polymerization electric current reached 30 coulombs, a total weight of 15.0
A film-like polyaniline with Rg deep green color and entangled fibrils was obtained. The average polymerization potential is 〇/A
The voltage was 0.74 V with respect to the gCJI reference electrode.

Next, this polyaniline together with the platinum plate was immersed in ammonia water having a concentration of 28 deuterium for about 1 hour.

While immersed in ammonia water, ultrasonic waves were applied for about 1 minute. Next, the polyaniline film together with the platinum plate was transferred to distilled water, and the above operation was repeated twice. Finally, the polyaniline together with the platinum plate was washed with distilled water for about 1 hour, and the pH of the washing water was 7.1. Then 200℃
After drying, the weight of the polyaniline was 10.0 cm and it was yellow in color.

(Configuration of experimental cell) For the positive electrode, the platinum plate itself was used as a current collector, using the polyaniline obtained on the platinum plate by the above operation, and for the negative electrode, L; and AJ were used.
30 mg of alloy powder with an atomic ratio of 50:50 was spread on a nickel wire mesh and pressure-molded into a shape of 15 Mφ at about 350°C. A nickel wire was pulled out from a part of the nickel wire and used as a negative electrode lead wire. . The exposed portion of the nickel wire was sealed with polytetrafluoroethylene shrink tubing.

As the electrolyte, L i B Fa of 1 mol/ρ permeability is used.
with propylene carbonate in a volume ratio of 1:1 and 1.2-
In addition to the dimethoxyethane solution dissolved in the mixed solvent, add 0.5g 1% of lithium fluoride to the mixed solvent.
The one added was used.

The experimental cell shown in FIG. 1 with the above configuration was used.

(Battery performance test) First, the assembled battery was tested in 2. 1 until the voltage reaches OV.
．． Although discharge was carried out at a constant electric density of 0 mA/as2, almost no current flowed. Next, the battery was immediately charged at the same current density until the battery voltage reached 4.0 square meters, and thereafter the above operation was repeated under the same conditions. At the fifth cycle, charging mW, O1, and discharge electricity R become almost constant, and the amount of electricity is 5.5
It was 0 coulombs.

Thereafter, the above charging and discharging process was repeated until the 10th cycle, when the battery system was left open for 168 hours and a self-discharge test was conducted.
33 coulombs, and the self-discharge rate for 7 days was 5.7%.

Roughly speaking, when this battery was repeatedly tested for charging and discharging, the charging and discharging efficiency was maintained at 90%, but the charging/discharging electricity t gradually decreased, and the discharging electricity m decreased to 2.75 coulombs. The cycle life was 313 times.

The energy density per weight of positive and negative electrodes determined from the discharge curve of this battery at the 9th cycle is 106 wh/)
It was t9.

Comparative Example 1 Instead of the electrolytic solution used in Example 1 (experimental cell configuration), lithium fluoride was not added and 1 mole/Nl 1 degree of 1BF4 was mixed with propylene carbonate at a volume ratio of 1:1. A battery performance test was conducted in exactly the same manner as in Example 1, except that a solution dissolved in a mixed solvent of 2-dimethoxyethane was used as the electrolyte.

As a result, at the fifth cycle, the charging/discharging efficiency was 97%, but the maximum discharge electricity fi was 5.30 coulombs. After that, both the charging and discharging efficiency and the discharge electricity σ gradually decreased. After the 10th cycle of charging was completed, the self-discharge rate for 7 days was examined in the same manner as in Example 1 and found to be 18.5%.

Furthermore, when a repeated charging/discharging test was conducted, at the 173rd cycle, the air release rate (a) also decreased to 2.65 coulombs.

The energy density determined from the discharge curve of this battery at the fifth cycle was 93Wh/kg.

Example 2 (Production of polyaniline) I N -HCρ with aniline concentration of 0.22 mol/fJ
While stirring 100 cc of aqueous solution with a magnetic stirrer, add (NH
4) 2S208 was added to chemically polymerize aniline.

The obtained polyaniline was in powder form.

After washing this polyaniline several times with distilled water, it was heated at 100℃ for 2 hours.
Drying was carried out under reduced pressure for 4 hours.

(Preparation of positive electrode) Next, from the polyaniline treated above, 10.0%
Rg was taken out, and 1.0 Rg of polytetrafluoroethylene powder as a binder and 1.0 ms of carbon black as a conductive agent were added thereto, and the powder with a total weight of 12 and ORg was well mixed. Next, this mixture was molded onto a 10 mmφ disc so as to include a platinum wire mesh current collector therein. A platinum wire was taken out as a lead wire from a part of the platinum wire mesh, and the lead wire portion was sealed with a polytetrafluoroethylene shrink tube to prevent the lead wire from coming into direct contact with the electrolyte.

(Preparation of negative electrode) Aluminum plate with a purity of 99.9% (thickness 100μTrL)
) was washed for 20 seconds with an aqueous NaOH solution having a concentration of 7 mol/ρ, washed several times with distilled water, and dried under reduced pressure.

Next, the aluminum surface was polished with emery paper in an argon gas atmosphere, washed several times with 1,2-dimethoxyethane, and air-dried in an argon gas atmosphere.

Next, this aluminum plate was cut into a disk shape of 10 mm with a portion left as a lead wire, and the lead wire portion was sealed with a shrink tube made of polytetrafluoroethylene. The weight Gl corresponding to a 10 sφ disc-shaped aluminum was 20.0 ■.

This aluminum electrode and a counter electrode of 100 ml of lithium metal crimped onto a nickel mesh were immersed in a 1 mol lfJm solution of LiPF6 in tetrahydrofuran, and lithium was applied to the aluminum electrode at a constant electric density of 0.5 TrLA/cm2. It was deposited and alloyed electrochemically until the amount reached 35.0 coulombs. In this case, the inside of the aluminum pole, which was not electrochemically alloyed, was used as it was as an electrode substrate.

(Configuration of experimental cell) The polyaniline obtained in the above (fabrication of positive electrode) was used as the positive electrode, the i/8 alloy obtained in (fabrication of negative electrode) was used as the negative electrode, and 1 mol of the electrolyte was added to the electrolyte. /ρ'a degrees of LiPF6 dissolved in a mixed solvent of propylene carbonate and 2-methyl-tetrahydrofuran at a ratio of 1:1 (volume ratio),
Furthermore, 0.1 to 4 fi% of lithium fluoride was added to the mixed solvent port as an electrolyte, and the electrolyte was soaked between the two electrodes of a 0.5-wire polypropylene diaphragm. The experimental cell shown in FIG. 2 was constructed using the following.

(Battery performance test) First, 2.5mA/c! At a constant density of I2, current starts flowing from the discharge direction, and the cell voltage reaches 2. Discharging was terminated after one step to OV. Then perform the first charge,
Charge the electricity 9 with the same current density until it reaches 4.2 coulombs, then 2. The charging and discharging characteristics of this battery were investigated by repeatedly discharging, charging, and discharging to OV.

As a result, the relationship between the charge/discharge efficiency and the number of cycles after the first charge was as shown in FIG. 3(a), indicating extremely good cycle characteristics.

Comparative Example 2 Instead of the electrolyte used in Example 2 (experimental cell configuration), Li with a concentration of 1 mol/ρ was used without adding lithium fluoride.
PF6 with propylene carbonate in a volume ratio of 1:1
A battery performance test was conducted in exactly the same manner as in Example 2, except that a solution dissolved in a mixed solvent of -methyl-tetrahydrofuran was used as the electrolyte. As a result, the relationship between the number of cycles and charge/discharge efficiency was as shown in FIG. 3(b).

Example 3 (Preparation of negative electrode) MOCfJ, 50cm was placed in a glass container with a stirrer, and then 200ml of benzene was added dropwise and stirred well.
The mixture was reacted at 50° C. for 2 hours to obtain polyparaphenylene. This polyparaphenylene was once dried under reduced pressure, washed with a hydrochloric acid-methanol solution, further washed with methanol, and dried under reduced pressure again. Then 1 at 400°C under an inert atmosphere.
Heat treatment was performed for 5 hours.

Polyparaphenylene 10#I9 obtained by the above method, 20η of Li/A1 alloy powder with an atomic ratio of 50:50, and 3Rg of polyethylene powder as a binder were thoroughly mixed.

This mixture was placed on a nickel wire gauze and formed into a 15-dia. disc, and a nickel wire was pulled out from a portion to form a lead wire.

(Configuration of experimental cell) The positive electrode and electrolyte were exactly the same as in Example 1, and the negative electrode was polyparaphenylene prepared in the above (fabrication of negative electrode), and the experimental cell shown in Figure 1 was constructed. .

(Battery Performance Test) The charging efficiency of this battery after the fifth repetition of charging and discharging was 99%, and the discharge capacity at that time was 4.46 coulombs. After charging for the 10th cycle, the battery system was left in an open circuit for 168 hours and a self-discharge test was performed.The discharge electricity m after being left unused showed 4.07 coulombs, 7
The daily self-discharge rate was 8.6%.

The cycle life of this battery was 283 times until the discharge capacity became 2.3 coulombs or less.

In addition, the energy density per weight of the positive electrode and negative electrode determined from the discharge curve at the 9th repetition was 101.3Wh/
It was 9.

Comparative Example 3 A battery performance test was conducted in exactly the same manner as in Example 3, except that an electrolyte to which lithium fluoride was not added was used instead of the electrolyte used in Example 3 (experimental cell configuration). Ta.

As a result, the charging/discharging efficiency of this battery was 97% after the ninth repetition of charging/discharging, and the discharge capacity at that time was 4.37%.
It was Coulomb.

Further, the self-discharge rate at the 10th cycle was 18.3%, and the cycle life was 149 times.

Also, the energy density determined from the discharge curve at the 9th repetition was 92. Owh/kg.

Comparative Example 4 Instead of the electrolyte used in Example 1 (experimental cell configuration), 1 mol/1 lilD of L+BF4 was added at a volume ratio of 1=
The same procedure as Example 1 was used, except that the electrolytic solution was prepared by dissolving propylene carbonate and 1,2-dimethoxyethane in the mixed solvent of Example 1 and adding 6% of lithium fluoride to the mixed solvent m. A battery performance test was conducted in exactly the same manner.

As a result, at the fifth cycle, the maximum charging/discharging efficiency was 98% and the amount of released iW was 539 coulombs, but thereafter, both the charging/discharging efficiency and the amount of discharged electricity gradually decreased.

After the 10th cycle of charging was completed, the self-discharge rate for 7 days was examined in the same manner as in Example 1 and found to be 20.3%.

Furthermore, when a repeated charging and discharging test was conducted, the charging and discharging efficiency fell below 50% at the 87th cycle, and the discharge electric bacteria at that time also decreased to 2.26 coulombs.

The energy density determined from the discharge curve of this battery at the fifth cycle was 96 wh/Icg.

Example 4 (Preparation of positive electrode) Purity: 99.9%, temperature: 20 s, 300°C: 24
10 hours from V2O5 obtained by drying under reduced pressure. OIItg
Take it out and add 1.0ffi of polytetrafluoroethylene powder as a binder to it! J, and carbon black 1 as a conductive additive. OrItg was added to the total amount of 12. O
#19 powder was mixed well. Next, this mixture was molded onto a 10-layer φ disc so as to include a nickel wire mesh current collector therein.

A nickel wire was taken out as a lead wire from a part of the nickel wire mesh, and the lead wire portion was sealed with a polytetrafluoroethylene shrink tube to prevent the lead wire from coming into direct contact with the electrolyte.

(Construction of Experimental Cell) The same composition as in Example 2 was used for all songs using v205 obtained in the above-mentioned procedure (Preparation of Positive Electrode) as the positive electrode, and the experimental cell shown in FIG. 2 was constructed.

(Battery performance test) The charging and discharging efficiency of this battery after the fifth repetition of charging and discharging was 99.5%, and the discharge capacity at that time was 4.7%.
It was 0 coulombs. After charging and discharging Ti for the 10th cycle, the battery system was left open for 168 hours and a self-discharge test was performed.The discharge electric nail after being left unused showed 4.52 coulombs, indicating a 7-day self-discharge rate. was 3.8%.

The cycle life of this battery was 148 times until the discharge capacity became 2.3 coulombs or less.

Comparative Example 5 Instead of the electrolyte used in Example 4, without adding lithium fluoride, LiPFe with a concentration of 1 mol/'' was added at a volume ratio of 1=
A battery performance test was conducted in exactly the same manner as in Example 4, except that a solution of No. 1 in a mixed solvent of propylene carbonate and 2-medylene tetrahydrofuran was used as the electrolyte.

As a result, the charging/discharging efficiency of this battery after the fifth repetition of charging/discharging was 99.4%, and the discharge electricity m was 4.
It was 69 coulombs.

Further, the self-discharge rate at the 10th cycle was 7.8%, and the cycle life was 86 times.

[Effects of the Invention] As described above, in the secondary battery according to the present invention, an alkali metal fluoride is added to an electrolytic solution, and the concentration of the alkali metal fluoride is adjusted to 0.
By setting the ratio to 001 to 2ffiff1%, the battery has a higher energy density and maintains high charge/discharge efficiency compared to a secondary battery using a non-aqueous electrolyte in which no alkali metal fluoride is added to the electrolyte. Moreover, it has extremely long cycle life and high performance characteristics.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views of a battery experimental cell, and FIG. 3 is a diagram showing the relationship between charge/discharge efficiency and cycle number in Example 2 and Comparative Example 2. 1... Positive electrode 2... Negative electrode 3... Positive electrode lead wire sealed with a polytetrafluoroethylene tube 4... Negative electrode lead wire sealed with a polytetrafluoroethylene tube 5... Electrolyte 6...Glass container 7...
・Negative electrode 8... Polypropylene diaphragm 9... Positive electrode 10... Positive electrode lead wire sealed with a polytetrafluoroethylene tube 11... Negative electrode lead wire sealed with a polytetrafluoroethylene tube 12...Polytetrafluoroethylene container patent applicant Showa Denko Co., Ltd. Hitachi, Ltd.

Claims (1)

[Scope of Claims] In a secondary battery consisting of a positive electrode, a negative electrode, and a non-aqueous electrolyte, the negative electrode is made of an alkali metal alloy or a composite of an alkali metal alloy and a conductive polymer, and the electrolyte of the electrolyte has the following general formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [M is an alkali metal, X is B, P, As, Sb, Si,
an element selected from the group consisting of; n represents an integer of 4 to 6; ] It consists of a fluorine-containing alkali metal salt represented by the following and a nonaqueous solvent, and is composed of the following general formula MF [M represents an alkali metal. ] A secondary battery characterized in that the concentration of an alkali metal fluoride represented by the formula is 0.001 to 2% by weight based on the nonaqueous solvent.