JPS62154477A - Secondary battery - Google Patents

Abstract

PURPOSE:To prevent the collapse of a negative electrode in charge-discharge, to increase energy density, to decrease self-discharge rate, and to increase charge-discharge efficiency by using aniline group polymer in a positive electrode and a complex comprising lithium-aluminum alloy powder and magnesium powder in a negative electrode. CONSTITUTION:Polyaniline crystal is filtered, washed with a large amount of pure water, neutralized with aqueous ammonia, washed again, and dried, then filled in a mold, and press-molded at room temperature to manufacture a positive electrode. Lithium-aluminum alloy powder and magnesium powder are uniformaly mixed, and the mixture is filled in a mold having a shape of electrode, then press-molded to manufacture a negative electrode. Thereby, the collapse of the negative electrode is prevented, and a secondary battery having high energy density, low self-discharge rate, and high charge-discharge efficiency can be obtained.

Description

[Detailed Description of the Invention] 1 JUl = 1 JUl = Momme 1 The present invention is a high-performance battery with high energy density, low self-discharge rate, and high charge/discharge efficiency, which prevents TNL destruction of the negative electrode during charging and discharging. Regarding secondary batteries.

Toyota ShomaiCurrently, commonly used secondary batteries include lead-acid batteries and nickel-cadmium batteries. These secondary batteries have a single cell battery voltage of about 2.0V, and are generally aqueous batteries.

In recent years, research has been actively conducted on secondary batteries that use lithium as the negative electrode and conductive polymers, interlayer compounds, inorganic oxides, etc. as the positive electrode, as secondary batteries that can achieve high battery voltage. In particular, secondary batteries using a conductive polymer as a positive electrode and lithium as a negative electrode are expected to be used as high-energy density secondary batteries.

As the conductive polymer used as the positive electrode of the above-mentioned battery, conductive polymers having a conjugated double bond in the main chain such as polyacetylene, polythiophene, polyparaphenylene, and polypyrrole are known.・
H.Curfman.

JE φ double φ Kauf? -, N.J. L. Kogar, Earl Kerner, N.G. McDiarmid, Physics Review, 32nd exposure, p. 2327 (1982
), (J, H, aufman, J, W, Ka
wfer.

^, J, IIeger, R, ni ancr, A, G
, HacDiarmid, phys, Rev.

1 Go, 2327 (1982)>).

In addition, there has already been a proposal to use polyaniline obtained by oxidative polymerization of aniline as the 11th inverter for aqueous or non-aqueous batteries [N.G. McDiamide et al., Polymer Preprints, Vol. 25, Kame 2 ．． Second
48 pages (1984) Kuhachi, G., HacDiariid
et al., Polya+er, Preprints, 25.
Na2, 248 (1984)>, Sasaki et al.
Proceedings of the 50th Annual Conference of the Electrochemical Society, p. 123 (1983
), Electrochemical Society Box 51st Conference Abstracts, 228 pages (1
984)].

Considering the high energy density, low self-discharge rate, high charge/discharge efficiency, long cycle life, etc. of these THS polymers)!
Most preferably, polyaniline is used as the positive electrode. However, when performing a secondary battery reaction using lithium as the negative electrode layer active material and polyaniline as the positive electrode active material, dendrites are formed when lithium ions are reduced to lithium metal during charging, reducing charge and discharge efficiency. There are also problems such as short circuits between the positive and negative electrodes. Therefore, many new technologies have been reported to prevent dendrites and improve the charge/discharge efficiency and cycle life of negative electrodes. M
Abraham Kasa゛″Lithium Batches.

G.P. Calvano Collection, Academic Press, London (1983), H. Abraham
etal, in”L-Kuchijuum Batteries
”, J., P., Gabano.

editor, ^ academic press, Lon
(1983) )), a method of preventing lithium dendrites by adding additives to the electrolyte system, or alloying the negative electrode itself with aluminum [Japanese Patent Application Laid-open No. 108281/1983] has been proposed. There is. but,
The above method not only does not necessarily provide a satisfactory dendrite improvement effect, but also has problems such as the lack of lithium-aluminum. It has also been proposed to use a solid solution of silver and an alkali metal as a negative electrode (Japanese Unexamined Patent Publication No. 73860/1983). In this case, there is no collapse like in the alloy of lithium and aluminum, but there is less passage of the alkali metal that alloys quickly enough, and the metallic alkali metal may precipitate without being alloyed.To prevent this, The use of porous materials is recommended. Therefore,
The charging efficiency of large currents is poor, and batteries with a high proportion of alkali metals have problems such as gradual acceleration of micronization due to charging and discharging, resulting in a rapid decrease in cycle life.

Furthermore, we have developed a method in which lithium foil and aluminum foil are laminated to form a C laminate and then alloyed in an electrolytic solution to produce an electrode (U.S. Pat. No. 4,056,413 Specification 4), and lithium-aluminum alloy powder A method has been proposed in which an electrode is prepared by mixing lithium powder and press-molding the mixture (Japanese Unexamined Patent Publication No. 175366/1983). However, when the electrodes obtained by these methods are used as negative electrodes, the dendrite improvement effect is not necessarily satisfactory, and voltage flatness, high energy density, low self-discharge rate, and high charge-discharge efficiency (Chiyobi cycle cycle You can get a rechargeable battery with a long life!
There was no fall.

An object of the present invention is to overcome the drawbacks of the conventional secondary batteries, prevent collapse of the negative electrode during charging and discharging, have high energy density, and provide self-discharge. An object of the present invention is to provide a secondary battery with a low charge/discharge efficiency and a high charge/discharge efficiency.

IJ” 7
As a result of various studies to solve the drawbacks of the above-mentioned conventional techniques, the present inventors found that when a composite consisting of lithium-aluminum alloy powder and magnesium powder is used for the negative electrode,
The present inventors have discovered that a high-performance secondary battery that can achieve the above objects can be obtained, and have completed the present invention.

That is, according to the present invention, there is provided a secondary battery characterized by using an aniline polymer for the positive electrode and a composite consisting of lithium-aluminum alloy powder and magnesium powder for the negative electrode.

The composite used as a negative electrode in the present invention means a molded body made from a mixture of lithium-aluminum alloy powder and magnesium powder.

The Libram-aluminum alloy powder used as one of the constituent elements of the negative electrode in the present invention can have an elemental composition ratio of lithium to aluminum of 10:90 to 90:10, but practically it is High diffusion rate of lithium, 40:60 to 90:1
It is preferable to use it in the range of 0. 1. - Therefore, the particle size obtained by classification is less than 50 mesh, preferably 2
It is preferable to use the powder after drying it under reduced pressure at a temperature of 100 to 400°C. The above heat treatment I11! The impurities on the surface of the alloy powder are removed and mixed with the magnesium powder η′
Adhesion with magnesium powder improves when

The magnesium powder used as the other component of the main fiber of the negative electrode of the present invention has a melting point of about 650°C, is inert to solvents and supporting electrolytes, and is free of burrs, impurities, and eluates. It also has good electrical conductivity. :Blend 0 of magnesium powder is lithium-Al.

The amount is 1% to 50% by weight, preferably 5mff1% to 20tfifi1%, based on the Miniram alloy powder.

If the proportion of magnesium powder is less than 1% by weight, the effect of improving the disintegration properties during charging and discharging of the lithium-aluminum alloy will not be sufficient; on the other hand, if the proportion of magnesium powder is more than 50% by weight, the diffusion of lithium will be reduced. speed decreases,
The problem is that battery performance deteriorates.

has.

Examples of methods for producing a composite from a mixture of lithium-aluminum alloy powder and magnesium powder include the following method.

(1) One method is to uniformly mix a lithium aluminum alloy powder and a magnesium powder, then fill the mixture into a mold shaped like an electrode, and mold the mixture by applying pressure at room temperature.

The pressure at this time varies depending on the filling speed of the mixture, so it cannot be determined unconditionally, but in general, 0.2t/cIR2 to 5t/n2 is good, and the most preferable pressure range is 0.2t/cIR2 to 5t/n2.
cm2 to it/α2.

(2) A mixture consisting of lithium-aluminum alloy powder and magnesium powder is press-molded at room temperature by the same method as in (1) above, and then heated at a temperature below the melting point of the magnesium powder and higher than room temperature, or heated and pressurized. How to process.

(3) A method in which a mixture of lithium-aluminum alloy powder and magnesium powder is filled into an electrode-shaped mold, and heated and pressurized at a temperature below the melting point of the magnesium powder and above room temperature.

The pressure during the heating and pressure treatment in (2) and (3) above is the same as in (1) above.

In addition, the heating in the methods (2) and (3) above is
The temperature may be gradually raised from room temperature to the processing temperature, or it may be heated to the processing temperature from the beginning. (2)
In method (3), if the treatment temperature is higher than the melting point of magnesium, the effects of the present invention cannot be obtained. When the treatment temperature is room temperature, the method is similar to method (1) and no special significance is recognized, and when the treatment temperature is lower than room temperature, the effects of the present invention cannot be obtained.

Further, the heating time in the methods (2) and (3) above is selected depending on the treatment temperature, and the treatment temperature and treatment time are inversely proportional. For example, when the treatment temperature is 600°C, the desired time is 1 minute to 30 minutes, preferably 2 minutes to 15 minutes.

Among the methods (1), (2) and (3) above, methods (2) and (3) increase the degree of bonding between the lithium-aluminum alloy and magnesium, increase the electrode strength, and prevent collapse. It is preferable that the amount of carbon dioxide is lower than that of an untreated product that is not heat-treated at a temperature below the melting point of magnesium and higher than room temperature, and method (3) is particularly preferable.

゛ In addition, lithium-aluminum alloy powder is free from moisture,
Since it is highly reactive to oxygen, nitrogen, etc., operations such as crushing, mixing, molding, and heating are preferably performed under an inert gas atmosphere or under vacuum. 1. The aniline polymer used as the positive electrode in the present invention can be chemically polymerized by reacting an aniline monomer with an oxidizing agent such as ammonium peroxide or hydrogen peroxide;
It may be manufactured by any method such as an electrochemical polymerization method in which an electrode is placed in an acidic aqueous solution of an aniline monomer and an aniline polymer is oxidized and deposited on the positive electrode by applying electricity.

Representative examples of aniline monomers include aniline, 2-
Methoxyaniline, 3-methoxyaniline, 2.3-dimethoxyaniline, 2.5-dimethoxyaniline, 2.
6-dimethoxyaniline, 3,5-dimethoxyaniline, 2-ethoxy-3-methoxyaniline, 2,5-diphenylaniline, 2-phenyl-3-methylaniline,
Examples include 2,3.5-trimethoxyaniline, 2,3-dimedylaniline, and 2.3,5.6-titramedylaniline, and among these, aniline is preferred. Specific methods for producing aniline polymers are described in, for example, N.G. Green and N.E. Woodhard, Journal of Chemical Fussiati. No. 97 @ (1910).

Page 2388; Volume 101 (1913), No. 111
Page 7; N. Kitani and J. Izumi et al.; Britin Chemical Society of Japan, Vol. 57 (1984), Sen 8. It is described on page 2254.

The aniline polymer produced by the above method is often obtained in a form containing water and impurities, and if used as a positive electrode as is, these water and impurities may have a negative effect on battery performance. Since it has a high reactivity with lithium, it may reduce the self-discharge rate and cycle number. Therefore, it is preferable to wash and dry the aniline polymer to remove moisture, impurities, etc. before use.

The solvent for the electrolytic solution used in the secondary battery of the present invention is preferably aprotic and has a high dielectric constant. For example, ethers, ketones, amides, sulfur compounds, Nisder phosphate compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds, sulfolanes, etc. can be used, but among these, ethers , ketones, phosphate ester compounds, chlorinated hydrocarbons, carbonates, and sulfolanes are preferred. Representative examples of these 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, dimethylsulfony 1:side, dimethylthioformamide, ethyl phosphate, methyl phosphate, chlorobenzene, sulfolane, 3
-Methylsulfolane and the like can be mentioned.

These solvents can also be used in combination of two or more.

Furthermore, examples of supporting electrolytes used in the secondary battery of the present invention include Li PFe and li Sb Fe.

Li C104, Li As Fe, CF3 SO3
Li.

Li BF4, Li B (Bu)4.

Li B (C6H5) 4 , 1i B (Et) 2
Examples include (Bu)z, but are not necessarily limited to these. These supporting electrolytes are −
Class V may also be used in combination of two or more types.

The concentration of the supporting electrolyte cannot be unconditionally defined because it varies depending on the type of aniline polymer used in the positive electrode, charging conditions, temperature, FFI of the supporting electrolyte, type of solvent, etc., but it is generally 0. It is preferably within the range of 5 to 10 mol/ρ.

The electrolyte may be homogeneous or heterogeneous.

In the secondary battery of the present invention, the amount of dopant doped into the aniline polymer is 10 to 180 mol%, preferably 20 to 100 mol%, based on 1 mol of repeating units of the aniline polymer. be.

In a composite made of lithium-aluminum alloy powder and magnesium powder, it is advantageous to increase the utilization rate of lithium because it increases the energy density, but if all lithium is used, dendrites etc. are likely to occur. It is preferable to perform charging and discharging at a utilization rate of 10% to 90%.

The doping level and lithium utilization rate can be freely controlled by measuring the electrical groups flowing during charging.

It may be carried out either under constant current, constant voltage, or under varying conditions of current and voltage.

Next, the present invention will be explained in more detail by giving Examples and Comparative Examples.

Example (Preparation of positive electrode) 1N aqueous hydrochloric acid solution i with an aniline concentration of 0°22 mol/1
oo Id was externally heated while stirring mechanically to maintain the liquid temperature at 40°C. 0.2 as an oxidizing agent in the liquid
Ammonium persulfate ((N+-14) equivalent to 5 mol/1
2S208) was gradually added, polyaniline crystals were precipitated in the solution. After the addition of ammonium persulfate was completed, the temperature was maintained at 40° C. for 3 hours to complete the reaction. The polyaniline obtained was a powdery green-black crystal. The crystals were filtered, washed with pure water, and then neutralized with aqueous ammonia. After washing, washing with water was performed again. Next, drying was performed at 80° C. under reduced pressure for 5 hours until moisture disappeared.

10. Dried polyaniline 34j19. A positive electrode was prepared by filling a φ mold and press-molding it at room temperature.

Production of negative electrode (IJ) A lump of lithium-aluminum alloy with an elemental composition ratio of 50:50 manufactured by Suido Metal Co., Ltd. was milled using a ball mill.
Time crushed. The obtained aluminum alloy powder was classified on a 200 to 300 mesh sieve, and the powder was heated to 350° C. under reduced pressure and dried for 1 hour.

Magnesium powder is manufactured by Kojundo Kagaku Co., Ltd.
Classified on a sieve with ~300 mesh and heated at 150°C under reduced pressure.
It was dried at.

゛ The lithium-aluminum alloy powder and magnesium powder obtained by the above treatment were mixed at a ratio of 80 parts of the alloy powder to 20 parts of the magnesium powder, and mixed in a tumbler for 2 hours. , the alloy powder and magnesium powder were homogenized. 35μ of mixed powder 1
It was filled into a mold of 0 sφ, 0.5 t/ was 600 μm, and the density was 0.74 g/3.

(Structure of experimental cell) The positive electrode (polyaniline) and negative electrode (composite of lithium-aluminum alloy powder and magnesium powder) produced by the above method were assembled into the experimental cell shown in the figure, and between the positive electrode and negative electrode, A porous polypropylene diaphragm impregnated with an electrolytic solution in which 1 mol/Ill equivalent of lithium fluoroboride is dissolved in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane at a volume ratio of 1:1 is inserted to prevent short-circuiting between the two electrodes. Structure.

(Battery Performance Test) A repeated charging and discharging test was conducted under conditions in which the current density for charging and discharging was set at 3 mA/in 2 and the lower limit voltage during discharging was set at 1.0 ■. Charge/discharge efficiency is 97% at the 5th cycle
The electricity m at that time was 13.42 coulombs, and the lithium utilization rate was 15%. This battery had the same results even after the 300th cycle as the 5th cycle.
When the self-discharge test was conducted for 720 hours on the 01st time,
The self-discharge rate was 3.8%.

[1] Cycles were carried out under the same charging and discharging conditions as in the example, except that only a lithium-aluminum alloy was used as the negative electrode instead of the composite of lithium-aluminum alloy powder and magnesium powder used as the negative electrode in the example. A test was conducted. As a result, the charging/discharging efficiency was 93% at the fifth time. The amount of electricity that flowed at that time was 13.2 coulombs, and the utilization rate of lithium was 13.7%, but the Nykle number was 150.
The charging efficiency decreased to 80% in the second cycle, and when the self-discharge rate was measured in the next cycle, it was 80% after 720 hours. After the experimental run was completed, the battery cell was disassembled and the negative electrode was observed, and it was found that the electrode had collapsed so badly that it did not maintain its shape.

As described above, by using a composite made of lithium-aluminum alloy powder and magnesium powder as the negative electrode, it is possible to prevent the negative electrode made of lithium-aluminum alloy from collapsing, and to achieve high energy It has become possible to obtain secondary batteries that operate with high density, low self-discharge rate, and high charge/discharge efficiency.

[Brief explanation of drawings]

The figure is a schematic cross-sectional view of a battery cell for measuring characteristics of a secondary battery, which is an example of the present invention. 1... Nickel lead wire for negative electrode 2... Nickel testicular body for negative electrode 3... Negative electrode 4... Porous polypropylene diaphragm 5... Positive electrode 6... Nickel net conductor for positive electrode 7...Positive electrode lead wire 8...Teflon container Patent applicant Showa Denko Co., Ltd. Hitachi Ltd.

Claims (1)

[Claims] A secondary battery characterized by using an aniline polymer for the positive electrode and a composite consisting of lithium-aluminum alloy powder and magnesium powder for the negative electrode.