JPS6355868A - Operation of secondary cell - Google Patents

Abstract

PURPOSE:To make it possible to simultaneously satisfy high energy density, low self-discharge, high charge-discharge efficiency and a long cycle life by setting charge end voltage and discharge end voltage within a specific range. CONSTITUTION:In the operation of a secondary cell consisting of a negative electrode made of a lithium metal or its alloy, a positive electrode made of a polyaniline system compound complexed from an undoped state by proton acid and an electrolyte, whose solvent is made of a mixed solvent of propylene carbonate (PC) and 1, 2 dimethoxy ethane (DME), the secondary cell is operated within the range of voltage not exceeding 4.5 V, desirably not exceeding 4.3 V, specifically desirably not exceeding 4.1 V at the charge end and not less than 1.5 V, desirably not less than 1.7 V and specifically desirably not less than 1.9 V at the discharge end. Thereby, the cell performance having high energy density, high charge-discharge efficiency, a good cycle life, a small self- discharge rate and good flatness of voltage during the discharging process can be obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention has a high energy density, small self-discharge,
This invention relates to a method for operating a secondary battery that has a long recycle life and good charge/discharge efficiency (Coulomb efficiency).

[Conventional technology]

So-called polymer batteries, which use a polymer compound with a conjugated double bond in the main chain as an electrode, are high energy)! - It is expected to be used as a high-density secondary battery. Many reports have already been made regarding polymer batteries, for example, BJ Nigley et al.
Society, Chemical Comunication 3, 197
9, p. 594 (P. J. Nigrcy et at
, J,C,S,,Chem,Commun,,t97
9゜594), General Electrochemical Society, 1981, p. 1651 (J, [Iec
trochem.

Soc,, 1981.1651], JP-A-56-1
No. 36469, No. 57-121168, No. 59-38
No. 70, No. 59-3872, No. 59-3873, No. 59-t96566, No. 59-196573, No. 59-203368, No. 59-203369, etc. can be mentioned as some of them.

In addition, proposals have already been made to use polyanine, which is obtained by electrolytically oxidative polymerizing aniline, as an electrode for aqueous or non-aqueous batteries (A.G. Matsuku Diamide et al., Polymer Preblinds, Vol. 25, No. 2, p. 248 (1984) (A, G, HacD
iarmid et al, Polymer Pre
prints, 25°NG2.248 (1984)
＞ , Sasaki et al., Abstracts of the 50th Conference of the Electrochemical Society, 1
23 (1983), Proceedings of the 51st Conference of the Electrochemical Society, 228 (1984)).

[Problem that the invention seeks to solve]

However, when oxidized polymers of aniline compounds are produced,
Since it is obtained in a somewhat oxidized form, when it is used as it is or after alkali treatment for the IF electrode of a battery, the doping level is at most 50 mol%, and therefore it has been difficult to obtain a high energy density battery. In addition, polymer batteries using such oxidized polymers of aniline compounds as positive electrodes have not been able to simultaneously satisfy low self-discharge, low discharge efficiency, and long cycle life.

Therefore, an object of the present invention is to provide a method for operating a secondary battery that simultaneously satisfies high energy density, low self-discharge, high discharge efficiency, and long life.

[Means for solving problems]

The present inventors have achieved the goal of satisfying the four battery performances at the same time.
Is the secondary battery lr? As a result of careful consideration, we found that a polyaniline compound complexed with a protonic acid was used as the positive electrode, Sf-ram metal or its alloy was used as the negative electrode, and the solvent of the electrolyte was propylene carbonate (propylene carbonate).
(hereinafter referred to as PC) and 1,2-dimethoxyethane (hereinafter referred to as D
In the operating method of a secondary battery that is a mixed solvent of
．． The present invention was achieved by discovering that the above-mentioned four battery performances can be satisfied at commercial times by carrying out the test within a range of 5.5 or more.

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

The polyaniline compound used in the present invention is obtained by oxidative polymerization of an aniline compound represented by the following general formula (1).

Be3 Ba4 (However, R+, R2, R3 and R4 may be different or the same and represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms. ) Representative examples of the aniline compound represented by the general formula (1) include aniline, ortho- or meta-toluidine,
Xylidine, ortho or meta-anisidine, 2,5-dimethoxyaniline, 2,5-jethoxyaniline, 3.
Examples include 5-dimethoxyaniline and 2,6-dimethoxyaniline, but aniline is preferably used from the viewpoint of obtaining a secondary battery with good energy density.

The above-mentioned aniline-based oxidized polymer can be produced by either electrochemical polymerization or chemical polymerization.

When using the electrochemical polymerization method, the polymerization of aniline compounds is carried out by anodic oxidation, and for this purpose, for example, 2
Current densities of ~20m8/cI are used, often 1
A voltage between 0 and 300 volts is applied. The polymerization is preferably carried out in the presence of an auxiliary liquid in which the aniline compound is soluble, for which water or a polar solvent can be used. When using a water-miscible solvent, a small amount of water may be added. Suitable organic solvents are alcohols, ethers such as dioxane, tetrahydrofuran, acetone, acetonitrile, benzonitrile, dimethylformamide or N-methylpyrrolidone.

Polymerization takes place in the presence of a supporting electrolyte. This includes BF4-, As R4- as anions.

As R6-, Sb R6-, Sb Cj-, PFs
−.

Cj04-. 1" 804- and 804"- groups. The resulting oxidized polymer is a complex compound with the corresponding anions.

These salts contain, for example, quaternary ammonium, lithium, sodium or potassium cations as cations.

The use of compounds of this type is known and is not the subject of the present invention.

In order to produce an oxidized polymer of an aniline compound by a chemical polymerization method, for example, the aniline compound can be polymerized in a strong acid aqueous solution using a peroxide of different types. According to this method, an oxidized polymer of an aniline compound is obtained in the form of a fine powder. Since anions are present in these methods as well, the oxidized polymer of the aniline compound becomes a complex compound with the corresponding anions.

The inorganic peroxide used in the chemical production of oxidized polymers of aniline compounds is not particularly limited as long as it dissolves in a strong acid aqueous solution, and examples include ammonium persulfate, potassium persulfate, hydrogen peroxide, Avi ammonium acid-Fe (I[>ion redox system, hydrogen peroxide-
Examples of Fe (II) ion redox systems include potassium dichromate, potassium permanganate, and sodium chlorate, but from the viewpoint of obtaining a secondary battery with good battery performance, ammonium persulfate, ammonium persulfate-Fe
(If) Ionic redox system, hydrogen peroxide-Fe (
II) Ionic redox systems are preferred.

In the present invention, first, a doped polyaniline compound is undoped.

Methods for making a doped polyaniline compound into an undoped letter include (1) a method of compensating a doped polyaniline compound obtained by a chemical oxidative polymerization method or an electrochemical oxidative polymerization method with an alkali; (i) A method of electrochemically undoping a doped polyaniline compound obtained by a chemical oxidative polymerization method or an electrochemical oxidative polymerization method, 0. A method of undoping the polyaniline compound of the doped letter by heat-treating it at a temperature range of 100 to 300° C. is mentioned.

Since the polyaniline compound obtained by the Grignard method is undoped, it can be directly complexed with protonic acid.

Among the methods (1), (1) and 0 above, method (1) is preferred. Examples of the alkali used in method (1) include ammonia water, aqueous ammonia, sodium carbonate, potassium hydroxide, sodium hydroxide, and other non-molecular bases, and triethylamine and other lower aliphatic amines. Among them, ammonia water is preferred.

Even if the thus obtained undoped polyaniline compound is used as it is in the positive electrode of the secondary battery of the present invention, the remarkable effects of the present invention cannot be obtained.

Therefore, in the present invention, an undoped polyaniline compound is complexed with a protic acid.

The undoped polyaniline compound may be complexed with protonic acid as it is, but it is preferable to remove components that dissolve in the electrolyte used in secondary batteries before complexing it with protonic acid. good.

Although there are no particular restrictions on the method for removing components dissolved in the electrolyte used in the secondary battery targeted in the method of the present invention (hereinafter referred to as the secondary battery of the present invention), a method of cleaning with an electrolyte is usually used. , a method of washing with an organic solvent, a method of extraction with a vitic solvent, etc. are used.

The method of washing with an electrolytic solution or a 0-grain solvent is not particularly limited in terms of the presence or absence of stirring, the number of times of washing, the time, etc., as long as the washing is carried out until the electrolytic solution or organic solvent for washing is no longer colored. The temperature is usually in the range from the freezing point to the boiling point of the organic solvent in the Shimen solvent or electrolyte.

As a method for extraction with an organic solvent, a method such as Soxhlet extraction is employed. In this case as well, there are no particular limitations as long as the conditions do not cause the extract to become colored, but it is usually desirable to carry out the process in an inert gas atmosphere such as nitrogen or argon.

There is no particular restriction on the type of electrolytic solution used for cleaning the polyaniline compound, and for example, the electrolytic solution used in the secondary battery of the present invention described later can be used.

Furthermore, there is no particular restriction on the type of organic solvent used for washing or extracting the polyaniline compound, and any organic solvent may be used as long as it can remove components that dissolve in the electrolyte of the secondary battery of the present invention. Good too. That is, washing or extraction may be performed with the organic solvent itself used in the electrolyte of the secondary battery of the present invention, or with an organic solvent having a solubility parameter similar to that of the polyaniline compound, such as carbonyl such as acetone. There is no problem in cleaning or extracting with a compound, a nitrile compound such as acetonitrile, a chlorine compound such as dichloroethane, a carboxylic acid compound such as acetic acid, an amide compound such as dimethylbormamide, or the like.

Although there are no particular limitations on the method of complexing a polyaniline compound with a protonic acid, a method of stirring in an acidic aqueous solution containing the corresponding anion and having a pH of 3 or less is usually used.

The protonic acid anion used for complexing is CJ
halogens such as -, F-, 3r-, primary such as BF4-
Halides of group 1a elements, PFs −, As R6−
, Sb, Fs-, Group Ia-based halides, C
lO2-, H8O4-.

Examples include SO42-. Among these anions, preferred are CJ- and 8F4-.

CuO2- is mentioned, and BF is particularly preferable.
4- is given. These anions may be different or the same as the anions used in the battery electrolyte,
Preferably, they are the same.

The shape of the polyaniline compound when making the polyaniline compound of the doped letter into an undoped letter J3, and the shape of the polyaniline compound when the polyaniline compound of the undoped letter is complexed with protonic acid can be in the form of powder or film. Alternatively, it may be formed into an electrode.

Molded bodies that can be used as Ti electrodes can be obtained by various methods. For example, when the polyaniline compound is in powder form, a molded body can be produced by press-molding the powder by a known method. Often room temperature ~ 3
Temperature of 00℃ and 10~10,OOONg/ct
! pressure is used.

Lithium metal or an alloy thereof is used as the negative electrode of the secondary battery used in the present invention. Lithium metal alloys used include Li/A4 alloy, Ll/HCI alloy, Lt/zn alloy, Li/Cd alloy, Li/Sn alloy,
Li/Pb alloys and alloys of three or more metals containing alkali metals used in these alloys, such as Li/Aj
/~la, Li/AJ/Sn, Li/AJ/Pb
, Li/Aj/Zn, Li/ΔJ/f-1a, and the like. These alloys may be manufactured by either an electrochemical method or a chemical method, but
Those alloyed by an electrochemical method are preferred.

The polyaniline compound used as the secondary electrode of the present invention may include other suitable conductive materials, such as carbon black, acetylene black, metal powder, metal fibers, etc., as is well known to those skilled in the art. , charcoal S II let, etc. may be mixed.

In addition, polyethylene, modified polyethylene, polypropylene, polytetrafluoroethylene, ethylene-propylene-diene ether polymer (EPDM), sulfonated E
l) It may be reinforced with thermoplastic resin such as DM.

The solvents of the electrolyte of the secondary battery used in the present invention are PC and D.
It consists of a mixed solvent of ME, and there is no particular restriction on the mixing ratio, but the volume ratio of propylene carbonate is usually 20 to 80%, preferably 30 to 70%,
Particularly preferably 40 to 60%.

Typical cationic components of the supporting electrolyte used in the electrolyte of the secondary battery of the present invention include, for example, metal cations of metals whose Boring electronegativity value does not exceed 1.6 or whose general formula is R4-xMH+ M× or R3E+ (However, R is an alkyl group having 1 to 10 carbon atoms or an aryl group, M is N, P or As atom,
E is 0 or an S atom, X is an integer from 0 to 4). In addition, typical anion components of the supporting electrolyte include, for example, ClO2-, P
Fs-.

As Fs-, As R4-, 503CF3-.

BF4-1 and BR4- (However, R has 1 to 1 carbon atoms
0 alkyl group or aryl group).

A specific example of the supporting electrolyte is l-i PF6.

L! Sb R6, Lt ClO2, Li As R6
.

CF3 803 Li, Lf BF4, L
f B (80)<.

LiB(Et)2(Btl)2, Na
PFs.

Na BF< , Na As Fil , N
a B (80)4.

Examples include KB (BU)4, KAs Fe, but are not necessarily limited to these.

These supporting electrolytes may be used alone or in combination of two or more. A preferred supporting electrolyte is Lf
CjOa, LiAsFs.

Among LiBF4 and Lf PFs, LiBF4 is particularly preferred.

The concentration of the supporting electrolyte cannot be unconditionally defined because it varies depending on the type of polyaniline compound used in the positive electrode, the type of cathode, charging conditions, operating temperature, type of supporting electrolyte, type of organic solvent, etc., but in general 0.5~1
It is preferably within the range of 0 mol/''. The electrolyte may be homogeneous or heterogeneous.

In the secondary battery of the present invention, the amount of the dopant doped into the polyaniline compound is 40 to 100 mol%, preferably 50 to 100 mol%, based on 1 mol of repeating units of the oxidized polymer.

A feature of the present invention is that a secondary battery consisting of the above-mentioned components has a charging end voltage of 4.5V or less, preferably 4.3V or less.
Particularly preferably 4.1V or less, with a discharge end voltage of 1.5V.
or more, preferably 1.7v or more, particularly preferably 1.9v
The purpose is to operate within a 1f pressure range of V or more. Within this voltage range, any of the constant current method, constant voltage method, current pulse method, and voltage pulse method can be used.

If the voltage range is 4.5V or more or 1.5V or less,
This is undesirable because decomposition of the electrolyte and/or reaction between the electrolyte and the electrode active material occurs, which adversely affects battery performance.

In the present invention, if necessary, a porous membrane made of synthetic resin such as polyethylene or polypropylene or a natural miscellaneous paper may be used as the diaphragm.

In addition, some of the electrodes used in the secondary battery of the present invention may react with oxygen or water and reduce the performance of the battery, so the battery should be sealed and substantially oxygen-free and water-free. It is preferable that the letter be from

〔Example〕

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

Example 1 <Production of undoped polyaniline> 400 d of pre-deoxidized distilled water and 100 ml of 42% HBF4 aqueous solution
The mixture was placed in a three-necked flask, and nitrogen gas was bubbled through it for about 1 hour while stirring. Thereafter, the inside of the system was placed under a nitrogen gas atmosphere, a thermometer and a condenser were attached, and then the flask was cooled with water and ice to bring the solution temperature to 15°C. To this was added 20.0 g of aniline. After the aniline was dissolved, ammonium persulfate 229 was gradually added, and the mixture was heated to internal temperature while stirring.

The mixture was reacted for 5 hours while keeping the temperature below 25°C. After the reaction, the greenish-brown reaction solution was filtered and dried under vacuum to obtain 15 g (q) of a dark green product.
Soaked in 300 d of 0% ammonia water, stirred at room temperature overnight), filtered, washed with 10007 distilled water, and then heated to 80°C.
It was vacuum dried for 15 hours.

Then, further 1.2-Tume1-xy]-tan 1010
The resulting purple powder was immersed in 0O for 5 hours at room temperature (stirred), filtered, washed with 500d of 1,2-dimethoxyethane, and dried under vacuum at 80°C for 15 hours. The elemental analysis value of C-1-H-1-N mold type % is 9936, and the composition ratio is C: H: N = 6.0
0 : 4.51 : 0.99, and the following formula (2)
The polyaniline was shown to be undoped polyaniline.

<Complexation of protonic acid to undoped polyaniline>
3F, immersed in water-soluble Kl 500d, TY: n'T
- Stirred for approximately 3021 minutes. Then filtered for 500 m
2. Wash with distilled water at 80° C. 1511.1. After vacuum drying for a while, the Fuchi color powder was collected.

<Battery experiment> The polyaniline powder obtained in the above-mentioned process of complexing polyaniline with butonic acid in the doped letter was pressure-molded into a disk shape with a diameter of 20 mil, and lithium foil. Diameter 201M cut out from (thickness 200μTrL)
A battery was constructed using 11 disc-shaped materials as positive and negative electrode active materials, respectively.

FIG. 1 is a schematic vertical cross-sectional view of a battery cell for measuring characteristics of a secondary battery of the present invention, in which 1 is a platinum lead wire for the negative electrode, 2 is a platinum wire mesh current collector for the negative electrode with a diameter of 20 m and 80 meshes, and 3 is a disc-shaped negative electrode with a diameter of 20 m, 4 is a circular porous polypropylene diaphragm with a diameter of 20 m, and is thick enough to be sufficiently impregnated with the electrolyte, 5 is a disc-shaped positive electrode with a diameter of 20 m, and 6 is a diameter 20
III! R, 80 mesh platinum wire mesh current collector for positive electrode, 7 is a positive electrode lead wire, and 8 is a screw-type polytetrafluoroethylene container.

First, the platinum wire mesh current collector 6 for the positive electrode is placed in the lower part of the concave portion of the container 8, and the positive electrode 5 is further placed on the platinum wire mesh current collector 6 for the positive electrode, and the porous polypropylene diaphragm 4 is placed on top of it. After sufficiently impregnating the electrolytic solution, the negative electrode 3 was stacked, the platinum lead wire 2 for the negative electrode was further placed on top of the negative electrode 3, and the container 8 was tightened to produce a battery.

The electrolyte was 1 mol/l of 1i3F+ dissolved in a mixed solvent of but-copylene carbonate and 1,2-diphtho-4-nidiethane (volume ratio 1:1), which had been distilled and dehydrated according to a conventional method.
J solution was used.

The battery thus prepared was discharged under a constant current (1,5+a^/ci) in an argon atmosphere until the battery voltage reached 1.5■. Then 1.0t
Charge the battery at a constant current density of 1A/cd until the battery voltage reaches 4.0V, and after a 5-minute rest time after charging, 1.
At a constant current density of 5eA/cj, the battery voltage is 2. The battery was discharged until it reached OV. After a 5 minute rest period after discharge,
Charging was carried out under the same conditions as described above.

As a result of this repeated charge/discharge test, the maximum discharge Furukawa was obtained at the 25th cycle, and the energy density per unit weight of the active material at this time was 318-Hr//(!7. The cycle life until the discharge capacity supply reached the maximum discharge capacity of 172 was 735 cycles, and the self-discharge rate after one week at the 50th cycle was 1.3%.

Examples 2 to 4, Comparative Examples 1 to 3 Battery experiments were conducted in the same manner as in Example 1, except that the batteries were operated in various voltage ranges. The results are shown in Table 1.

Table 1 Examples 5 to 7 Battery experiments were conducted in the same manner as in Example 1, with various electrolytes used. The results are shown in Table 2.

Table 2 Examples 8 to 10 Polyaniline compounds were obtained by polymerization and reduction treatment in the same manner as in Example 1, using various aniline compounds instead of aniline. Battery characteristics were measured in the same manner as in Example 1 except that these reduced polyaniline compounds were used for the positive electrode. The results are shown in Table 3.

Table 3 [Examples 11 to 13] Battery experiments were conducted in the same manner as in Example 1, except that various l-i alloys were used in place of the 1-i metal. The results are shown in Table 4.

Table 4 Comparative Example 4 A battery experiment was conducted in the same manner as in Example 1, using the polyaniline obtained in the production of the undoped polyaniline in Example 1 without complexing it in the llBF4 aqueous solution. . As a result, the energy density is 228) 1- hr
/ Kl, cycle life is 225 times, self-discharge rate is 39
．． It was 5%.

Examples 14 to 18 Instead of the 0IN-HBF4 aqueous solution used in the complexation of protonic acid to the undoped polyaniline of Example 1,
A battery experiment was conducted in the same manner as in Example 1, except that polyaniline complexed with various protic acid aqueous solutions was used. The results are shown in Table 5.

Table 5 [Effects of the Invention] As described above, the operating method of the secondary battery of the present invention provides high energy density, high charging/discharging efficiency, good cycle life, low self-discharge rate, and high efficiency during discharging. Battery performance with good voltage flatness can be obtained. Therefore, the lightweight and small secondary battery exhibits excellent performance, making it ideal for portable devices, electric vehicles, gasoline vehicles, and power storage batteries.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a battery cell for measuring characteristics of a secondary battery used in the method of the present invention. DESCRIPTION OF SYMBOLS 1... Platinum lead wire for negative electrode, 2... Platinum wire mesh current collector for negative electrode, 3... Negative electrode, 4... Porous polypropylene diaphragm, 5... Positive electrode, 6... For positive electrode Platinum mesh current collector, 7... Positive electrode lead wire, 8... Polytetrafluoroethylene container.

Claims (1)

[Claims] The negative electrode is lithium metal or its alloy, the positive electrode is a polyaniline compound complexed with protonic acid from an undoped state, and the solvent of the electrolyte is propylene carbonate and 1 or 2
- A method for operating a secondary battery made of a mixed solvent of dimethoxyethane, characterized in that the secondary battery is charged and discharged within a range where the end-of-charge voltage is 4.5 V or less and the end-of-discharge voltage is 1.5 V or more. How to drive.