JPS5848362A - Electrochemical battery with sulfur dioxide as cathode reducing agent - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates, more particularly, to electrochemical cells containing sulfur dioxide as a cathode depolarizer.

Such lightning chemical cells are useful in radio electronics, minicomputers, medical equipment, and weather equipment.

an anode made of an alkali metal, preferably lithium, having a high noble potential; an electrically conductive inert porous cathode; and a cathode depolarizer dissolved in a non-aqueous electrolyte and placed on the inert cathode. Or homomorphism! Is this an electrochemical cell with a cathode reducing agent in 1? It is publicly known.

The electrolyte has certain requirements, i.e., ionic conductivity,
It must have compatibility with the electrode material and solubility of discharge products. As a vehicle for electrolyte,
Organic solvents such as propylene carboxylate, acetonitrile, ethylene carboxylate, dimethyl sulfite, dimethoxyethane or mixtures thereof have been used.

can be increased, but the viscosity of the solution remains low. In addition to organic solvents, organic solvents such as sulfur, phosphorus, selenium oxyhalides, and phosphorus thiohalides can also be used. These are resistant to the influence of, for example, lithium and can be used in conjunction therewith as active cathode depolarizers.

The ionic acid content of the electrolyte is represented by a salt that is easily soluble in an organic solvent. Examples of these are lithium, eg perchlorate, tetrafluoroporate, hexafluorophosphate.

The basic properties required of these salts are that they be inert towards cathodic depolarizers and cathodic metals.

Based on the state of the cathode depolarizer, the above-mentioned vaporized cells can be divided into the following two groups.

a) Electrochemical cells with solid-phase cathode active substances 1 (metal oxides, chromates, metal halides, sulfides); reduction of the cathode reagent mostly occurs according to a solid-phase mechanism; b) dissolved in an electrosulfuric solution Electrochemical cells with cathode active materials such as sulfur dioxide and thionyl chloride.

The cathodic reduction of the active material dissolved in the electrolyte takes place on the surface of an inert electrode that has conductivity that does not interfere with the movement of electrons during the electrochemical reaction.

In LI-S02 type chemical cells, 8
When 02 is reduced cathodically, a reaction as expressed by the following formula occurs.

Lithium dithionite obtained by burning SO2+2+koL l -'L l 25204↓ is sparingly soluble in the electrolytic solution and precipitates on the surface of the inert electrode.

When lithium dithionite precipitates, the electrode surface becomes blocked and passivated, eventually slowing down the cathodic reduction reaction of sulfur dioxide (U.S. Patent No., ?, qj
,? , No. 23) Cyclic deltametry at zero smooth electrode (Cycl lc Volta+vtn
As shown in the results of Etry), the more negative the potential of the change in the scanning direction from cathodic polarization to anodic polarization, the more the anodic peak of oxidation of the 802-11 element product shifts toward the positive region. The value of this peak becomes high.

A similar relationship is specific to electrochemistry/reactions, but W
In the gas chemical reaction, the products do not dissolve in the electrolyte and accumulate on the W pole.

A similar reaction occurs in batteries having another active material dissolved in the electrolyte and in Ll-SOCJ2 batteries in which the active material of the cathode itself is a solvent.

^． N. Dey and P. fllro's paper (- pr l
mary t +/socl2cells' J. E
electrochem. Soc. , vol,/J.
, S+A10) includes SOCl2 on an inert cathode.
It is stated that during the cathodic reduction of , the following reaction proceeds.

G' L l +-2 SOCl2→Q L ICl↓
+SO2+S↓The in-phase consisting of LICI and S deposited on the cathode surface produces an immobility effect on the cathode surface.

To optimize the performance of cells in which in-phase products are formed during cathodic reactions, porous electrodes with an expanded inner surface are used as inert electrodes.

The solid phase reaction products are distributed into the pores and the surface passivation process is clearly more efficient than on a smooth electrode.

The above paper, which was written to study the cathodic reduction of S02 and 5OC12, states that when the reaction product is deposited in the ultra-fine pores of W, it expands, expands, and becomes thick and elastic. has been pointed out.

Due to the chain of reactions within the pole, the true current density at the electrode surface is lower than the calculated value. Therefore, a porous electrode with a specific range of current density values according to the electrochemical properties of a given system and the electrode structure , the polarization value will be lower than that of a smooth electrode. In cells where the cathode reaction products are deposited in phase on the cathode surface, it is the cathode process that limits their specific properties. In this regard,
The microstructure of the porous inert electrode influences the progress of the II process and also defines the operational efficiency of the chemical cell as a whole.

Electrochemical processes on porous electrodes are distributed non-uniformly with respect to the electrode surface. The rate of this process is maximum at the front surface and decreases gradually with electrode depth due to electroresistive effects in the pores and diffusion limitations for the active material 1[K in the pores.

With increasing current density, the process non-uniformity increases and it is expelled towards the front surface. The working surface of the push is reduced, the polarization becomes large needle, and all the limiting factors are greatly pronounced. If solid phase reaction products are collected, the process deteriorates as the insoluble material blocks the pores, interfering with the progress of the process within the electrode.

Therefore, compared to smooth tr*, on porous electrodes a surface layer participates in the electrochemical process, the thickness of which depends on all factors, including the IIV structure of the electrode, its properties and current density.

As mentioned above, the formation of in-phase products of the cathodic reduction reaction, e.g. lithium dithionide from S02) L125204
In the formation of 5O2, the cathodic process limits the pond properties of the 5O2 system. By changing the properties of the inert cathode, which is carried out by the reducing power of the deactivating material, it is possible to considerably increase the power and energy capacity of the battery.

Currently, inert porous electrodes are made from carbonaceous or metallic materials (U.S. Pat. No. 3, ff 92.3).
(see g.9). However, electric V# made of carbonaceous material!
has wide applicability. These include the following processes: compression molding, thermal spraying (spray+nl2), coating (spreadlng), and suction from the mother luzo.
ction-on-out of pulp). In all these processes, the prime material is pre-milled to the desired particle size, mixed with a binder and optionally a pore former and/or hydrophobizing agent, and in some processes further heat treated. USSR Inventor's Certificate No. 939 g) No. 0 includes the steps of applying a solution of the polymer in an organic solvent to a metal support consisting of a suspension of a mixture of carden black and graphite, and then drying the diagnostic cloth layer. A method of manufacturing an inert electrode for a battery is taught.

W chemical cells in which the anode is made of Zn (Ll, My#Na1Cal^l) and an electrolyte and the cathode active material is 5ocl2 are known in the art (U.S. Patent No. 3, g9/ +j See No. 1). Cathodic reduction of the active material present in the liquid phase is achieved by forming a layer of a mixture of acetylene carbon black (gO), graphite 17i (1%) and binder, 711% (wt. occurs at the surface of an inert cathode consisting of a three-dimensional N1 lattice with .

However, these electrochemical cells do not have the required discharge capacity and power.

The increase in power and energy capacity can be achieved by changing the macrostructure of the electrode as well as by increasing the concentration of the active material dissolved in the electrolyte and the formation of soluble cathode products that do not passivate the electrode surface. This can be achieved by minimizing passivation of the inert electrode surface by solid phase reaction products.

US Patent No.? , 9.29. ．． No. 507 ha Ll-
5o21M is taught. The electrolyte of this battery is “
This is a solution of lithium bromide dissolved in a mixture of acetonitrile and propylene cargenate.

From the point of view of an optimal conductive system, it is known in the art to use various proportions of propylene car, 7cetonitrile and lithium bromide as the electrolyte for Ll-9o2 cells (Japan RoP, 2003).

niang H, Y, 5ehlalkler C,,T
aylor H,, H112h rate day/S('1
2 batterles-Record / Oth
Intersoc.

Energy Convers, Eng, Conf
,, Newark Del.

/973”, New York, /973, Q3
(See 2-Q3A).

Electrochemical cells containing sulfur dioxide as the cathode depolarizer are known (see US Pat. No. flA3.!A7A/3).

The anode is made of an alkali metal and the cathode is a ferromagnetic material 11yl with a large surface area.

Depending on the nature of the salt dissolved in the organic solvent, the cathodic reduction product can be soluble or insoluble.

When using a salt of an alkali metal, an insoluble product is formed, and when using a tetraalkylammonium, an insoluble product is formed.

If insoluble products are formed, porous inert cathodes are used.

As the organic solvent, propylene carnate, acetonitrile, mixtures thereof, etc. are used.

However, the electrolyte used in this battery has relatively low solubility in sulfur dioxide.

The solubility of sulfur dioxide in the electrolyte of a W@chemical cell is low, and the sulfur dioxide vapor pressure above the solution increases as the fIjA degree increases, resulting in an increase in system pressure. This on the one hand limits the permissible working temperature range and on the other hand requires a high mechanical strength of the battery housing, which increases the weight of the battery.

Furthermore, this electrochemical cell is deficient in W discharge, power capacity, and power output.

The purpose of the present invention is to increase the discharge energy capacity of an electrochemical cell while maintaining its brightness.

Another object of the invention is to extend the working temperature range and improve the gravimetric properties of electrochemical cells.

The object of the present invention is to provide an anode made of a metal capable of reducing sulfur dioxide, an electrically conductive inert porous cathode, sulfur dioxide as a cathode depolarizer, an aprotic solvent and an anode metal that is inert to sulfur dioxide. and a non-aqueous electrolyte containing an active electrolyte salt, the upper inert cathode being preadjacently polarized at a potential of 9.3 to 4/7° with respect to the lithium electrode. The use of electrolyte batteries in which the aprotic solvent contains at least one organic solvent with a donor value of 20-10 is a problem.

In the electrochemical cell of the present invention, a more efficient inert cathode is used which reduces self-defense and increases the amount of active material, thus modifying the cell's volume and capacity characteristics. The use of an upper cathode electrode makes it possible to increase the power of an electrochemical cell while maintaining its size and weight, and on electrochemically treated electrodes it is possible to process at extremely high current densities. can proceed.

The donor value, which indicates the ability to form a complex, is 70 to 30.
The use of organic solvents increases the solubility of 5020, resulting in a higher energy capacity of the electrochemical treatment pond, an expanded working temperature range, improved gravimetric properties, and a reduction in its size. . The solubility of S02 in upper wh solvents and electrolytes based on it is based on the formation of covalent bonds between Lewis acid-802 and base-solvents with electron-dense centers, i.e. O, N, etc. Lithium or sodium, which has an exclusively negative potential, is used as the anode metal.1. It is recommended to use a carbonaceous material as an inert cathode.

It is also preferred that the electrochemical cell contains a mixture of propylene carbonate, acetonitrile and dimethylformamide, or a mixture of propylene carbonate and dimethylformamide to increase the conductivity.

The electrochemical cell of the present invention comprises a tif# made of a metal capable of reducing sulfur dioxide and a cathode made of a porous material inert to sulfur dioxide on which sulfur dioxide can be reduced. Contains.

The anode and cathode are immersed in a non-aqueous electrolyte containing sulfur dioxide as a cathode depolarizer, an aprotic solvent, and an electrolyte salt that is inert to the sulfur dioxide and the anode metal.

As SW, a metal is used which has a higher potential by 9 than sulfur dioxide in a non-aqueous system. Most preferred are sodium and lithium, which have high activity, low equivalent weight, and are virtually inert to sulfur dioxide.

As the cathode, any material is used that is electrically conductive and inert towards sulfur dioxide, but on which sulfur dioxide can be reduced.

"Inert" means that there is no interaction between the material and 502, ie, no chemical oxidation, physical degradation, or precipitation.

Preferably, a carbonaceous material is used as the cathode, which can be produced by conventional methods. Generally, during electrochemical reduction of S02, precipitation of insoluble products is observed on the vulva;
This prevents the reduction of ridges. For this reason, cathodes with large surface areas are used.

The cathode is q, 3~ with respect to the lithium electrode! ,? It has been found that pre-klll polarization at a potential of V improves the properties of the electrochemical cell over K when the parameters of the cathodic process are defeated.

A porous graphite electrode manufactured by a common method,
The propylene car is subjected to aerochemical anodic polarization in a non-aqueous electrolyte consisting of 50212% by weight of LICA'04.

Figure 1 shows the electrodes! ＠A typical curve illustrating the origin of chemical anode activation is shown. The force is the cathodic electrostatic charge (galvanosta) of the unactivated electrode.
tIc) curve. Curve 2 is the anode 1 curve of the electrode activation process. Curve 3 is a cathode curve with polarization as the pole. It is very clear that after this electrochemical treatment, the discharge capacity has increased considerably. The cathodic electrostatic curve corresponds to the 'reduction' of sulfur dioxide dissolved in the electrolyte.

Since the electrochemically activated 11 electrodes easily discharge the sulfur dioxide active material dissolved in the electrolyte, it is necessary to ensure that the discharge capacity increases. It was said that

For this purpose, a packed ground electrolyte, i.e. without sulfur dioxide, propylene carp,
Much research was done in the electrolyte consisting of /'o4. The results thus obtained are shown in the table. As is clear from this graph, the length of the anodic electrostatic curve, that is, the discharge time, remains virtually unchanged regardless of the liI polarization K of the electrode.

Therefore, pre-anodic polarization by improving the macrostructure or catalytic properties of the porous 11 electrodes can improve the utilization of the active material dissolved in the electrolyte, and therefore increase the energy capacity and /4' Increase the power.

It has been found that the S-equilibrium polarization of the electrode should be carried out at a potential of 3-4/'7 V, which corresponds to the potential of the chemical decomposition of the II#I electrode of the electrolyte.

Table 1 shows the potentials at which electrochemical decomposition of the electrolyte begins in the cathode and anode regions, for example on a platinum 11 electrode.

Table l Electrolyte, Cathode potential, Anode potential.

v v Lithium monochlorate delobylene cardenate solution 10 1A
A Dimethylformamide solution of lithium verchlorate 1/'
A3 lithium barchlorate acetonitrile solution 09 l
A? Dimethyl sulfoxide solution of lithium berchlorate 12 da3
From this table, it can be seen that lithium ions were prepared by a known method at a potential of 9.3 to 4/'7 V with respect to lithium tS in a non-aqueous forging solution based on an aprotic solvent used in electrochemical cells. When the inert electrode is subjected to pre-(#1 + physical anodic polarization), the discharge time of the 11 electrodes is increased by a large width KW, and the utilization of the active material (S02) dissolved in the electrolyte is increased. That's what I understand.

The pre-interposed W electrode is then introduced into the chemical cell.

As mentioned above, when thionyl fluoride is used as the cathode active material, the cathode reaction product is in the M phase and passivates the electrode surface, as in the case of S02. As, 9.3~q, rivf')1!r
L l/SO containing Ichiha pre-anodically polarized at
It seems possible to effectively use C/2 type batteries.

11! % characteristics of electrochemical cells! It was found that the polarity of the anode does not depend on the elapsed time.

Electrode-#! On the surface of life! is the discharge of the untreated electrode.

The quantity of electricity versus the anodic polarization can be expressed by the degree of activation, which is the ratio of the quantity of electricity discharged by the mole. The degree of activation depends on the initial macrostructure of the porous electrode, especially on the porosity.

Table 2 shows propylene cargenate, /MLlclO
■=24 in an electrolytic solution consisting of 4 and/or 1% S02
The properties of a porous graphite electrode with light ridges for a given period of time after anodic polarization at mA/cfI are shown.

The electrolyte salt used in the cell of the present invention is a salt that is readily soluble in a solution of an aprotic organic solvent and SO2, and is fairly inert towards the wf electrode material and feral dioxide.

Lithium 9-chlorate and lithium bromide are preferred because of their high conductivity.

Table - Storage time Activation degree day 9g 136g
/ DaIO'7
/ /, 2/3
/ From the standpoint of improving the solubility of sulfur dioxide and the discharge characteristics of the system, in order to increase the co-energy capacity, expand the working temperature range, improve the monomer properties, and reduce the size of the mold side chemistry. Studies were conducted using various aprotic organic solvents.

The resistance of the anode in the aprotic solvent was considered in selecting the components of the solvent mixture.

Thus, the solvents that passivate the lithium surface and increase its stability are propylene carbonate (pc) and dimethyl sulfoxide. It appears even when the strength is about %.

The higher the complex-forming bonding power of the aprotic organic solvent indicated by the donor value, the higher the solubility of S02 in that solvent and in the solution using that solvent as a pace. It is desirable to use a solvent with a donor value of 2θ to 30.

It is also possible to use a solvent mixture in which the donor values of at least seven solvents are within the specified ranges mentioned above to condition the electrolyte.

Table 3 provides solubility data for S02 in aprotic organic solvents as well as electrolytes based on the solvents.

All the above data are at 2sC,/atm. From Table 1, the solubility of SO2 is also affected by electrolyte salts.
It can be seen that the higher the solvation ability of the salt, the higher the solubility of SO2 in the electrolyte.

It has been found that an aprotic organic solvent mixture and an electrolyte based thereon exhibit additivity in terms of the solubility of 302. These data are shown in Table DA.

An important property of an electrolyte is its conductivity. Table 5 provides conductivity data for electrolytes based on each non-norotonous organic solvent and mixtures thereof.

This table shows that the introduction of a complex-forming solvent into the solvent mixture does not significantly impair the tetraelectricity of the electrolyte compared to an electrolyte based on a mixture of f, pyrenecarnate and acetonitrile. is clearly understood.

As is clear from Table 6, organic solvents such as those that dissolve sulfur dioxide well are useful for improving the discharge characteristics of the cathode. (in this case,
This is the product of time and current for the electrode potential to change by 2 Vt from its initial value. .

Table 6 shows the discharge characteristics of the cathode using cathode depolarizer 502 in a non-aqueous electrolyte (inert support-platinum, 3-electrode cell).

The electrochemical cell of the present invention has a large energy capacity. This is based on the fact that it is possible to use a small amount of effective inert electrodes, allowing a corresponding increase in the amount of active material and thus improving the weight and size characteristics of the cell. The energy capacity of the battery is also increased by the following facts: That is, by using a solvent that increases the solubility of 502, the content of 0302 in the system can be increased without increasing the mechanical strength and therefore without increasing the weight of the battery. I can do it. This battery is also characterized by a large ΔW. This may be possible because by using an electrochemically treated effective inert electrode and a solvent that increases the discharge rate, the process can be operated at extremely high current densities. Based on the fact that there is no need to change the weight and size of the cell, the electrochemical cell of the present invention further extends its working temperature range due to the low vapor pressure above the solution.

Hereinafter, the present invention will be explained in more detail by showing specific examples of the electrochemical cell of the present invention.

Example: An inert porous electrode prepared by compression molding graphite powder and used as a cathode of the electrochemical cell of the present invention is subjected to anodic polarization K at 4 ASV direct current in a three-electrode system.

In this system, the working electrodes include the above-mentioned graphite electrode, reference electrode - lithium electrode, auxiliary electrode - lithium electrode,
A 7M solution of L1α04 dissolved in KNI containing electrolyte-802/cow weight % is used. The results of the anodic activation of the inert electrode-cathode of H. are shown in Table 7.

Table 7, xs 3.4A Yu/'Zf 13 / Yu 9 Example co Inert porous electrode-cathode was used in a three-electrode system under the same conditions as in Example/ except that polarization was performed at a constant potential of 4 ASV. @0 Table gK attached to polarization shows data showing the effect of time on the degree of activation.

Table g / M3 Column 1 123 Example 3 As an electrolyte, /M dissolved in bripyrene carnate containing 802 and acefecylyl (/:3) was used as an electrolyte.
For #1 using the L.α04 solution, an inert porous electrode-cathode was subjected to anodic polarization at a potential of 1A4sv in a three-electrode system in the same manner as in Example 1, and the result was 90 I-2m.
The degree of activation at A/d K was 10.

EXAMPLE A stainless steel cylinder cell with a height of AO and a diameter of 33 is made. The clean, dry cell was placed in a box, which was filled with pre-dried, denitrated argon. The preparation of the electrolytic solution, which includes the step of dissolving and dissolving the aprotic organic solvent mixture trap salt and sulfur dioxide, is performed directly in this box9. This is a solution in which . The concentration of lithium bromide is i g mo/
For β, the ratio of propylene carzenate to acedinitrile is /: 3.3.502 concentration is tzs volume %.

The sulfur dioxide is passed through a drying system beforehand.

The aprotic solvent is predried and double distilled.

The salt recrystallizes and dries. In this cell, there is a lithium anode with a surface area of 1ioci and a surface species of 1Io.
OCD inert carbonaceous cathode. This carbonaceous inert cathode is preliminarily (drowsed) at a potential of 4 AsV with respect to the reference lithium electrode. The 1111 line voltage of this cell is
It is v. The discharge capacity 1 of this cell at a ring density of 125 mA/d is g^ hours at a voltage of 2.7 V.

Example S As the electrolyte, a lithium bromide solution dissolved in a mixture of propylene carbinate, a7toni)lyl, and dimethylformamide (/tomi, ?, ?:a5) was used, and the carbonaceous inert electrode was used as a preliminary anode. The battery described in Example D was used except that it was not polarized.

The open circuit voltage of this battery is 9V. Current density 125
The discharge capacity It of this battery in mA/- is the voltage unit 6
gv is gS^・time.

Example 6 Globylene force as an electrolyte? A cell was used as described in Example D, except that an Ig mol/l solution of lithium bromide in a mixture of ester, acetate, dimethylformamide, and dimethylformamide was used.

The open circuit voltage of this battery is YuqV. current density i2
! The discharge capacity at the m^ shoulder is gg^・ at the voltage AfV.
It's time.

Example 7 A cell as described in Example D was used except that a carbon inert cathode pre-anodized at a potential of 446 volts was used. The open circuit voltage of this battery is 9 AV. Current density 12! m^/
cI! When the discharge vessel is placed at I, the voltage is near v and the time is g.

[Brief explanation of the drawing]

Fig. 1 is a graph showing a typical sequence explaining the principle of electrochemical anodic activation of am, and Fig. 2 shows that even if the electrode is anodic polarized in a background electrolyte, Silly static electricity car! In other words, this is a graph showing that the quality of discharge time does not change. 1 2 Continued from page 1 0 Inventor Valenteina Ivanovna Litvynovya Soviet Union Dnepropestrovsk Prospekt War Geroev 49 Cavy 62 [Phase] Inventor Tamara Leontyevna Martynenko Soviet Soviet Union, Dnepropetrovsk Naberezhnaya Pobedei 48 K. 201 0 Inventor Leonid Polisovitch Raikelson Soviet Union Ningrad Naberezhnaya Lekki Moiki 112 Kev 28 0 Inventor Valentin Zakharovich Moskotsky Soviet Union Dnepropetrovsk Ulissa Gogolya 5 Kev 7

Claims (6)

[Claims] (1) An anode made of a metal capable of producing sulfur dioxide, a conductive inert porous cathode, sulfur dioxide as a cathode depolarizer, an aprotic solvent, sulfur dioxide, and the previous FB)
an electrochemical cell comprising a non-aqueous electrolyte containing an electrolyte salt inert to the weld 11iK, wherein the inert cathode has a lithium electrode of 11.3 to 4/? An electrochemical cell as described above, consisting of electrodes which are anodic prepolarized at a potential of <<> and/or characterized in that the aprotic solvent comprises an organic solvent of at least 7M with a donor value of 20-30. (2) The electrochemical cell according to claim 1, wherein the anode metal is lithium. (3) The electrochemical cell according to claim #/7, wherein the pre-metallic electrode is IJum. (4) An electrochemical cell according to claim 7 or 2 or 3, wherein the inert cathode is made from a base material. (5) The electrochemical cell according to any one of claims 7 to q, wherein the aprotic solvent contains a mixture of p-pylenecargenate, acetonitrile, and dimethylformamide. (6) The electrochemical cell according to any of claims 1 to q, wherein the aprotic solvent contains a mixture of propylene cargenate and dimethylformamide.