JPH03236168A - Chemical battery - Google Patents

Abstract

PURPOSE:To obtain a battery which has little danger of firing or inflammation and high electromotive force and a high discharge capacity and can be charged by using an organic silicon compound containing the silicon element in the molecule as an organic electrolyte for an electrolyte solvent. CONSTITUTION:An alkali metal is used for a negative electrode, a solid active material is used for a positive electrode, and an electrolyte is solved in an organic solvent containing at least one kind of a group of an organic silicon ether compound, an organic silicon ketone compound, an organic silicon sulfoxide compound, an organic silicon nitrile compound, an organic silicon amide compound, and an organic silicon imide compound in the molecule for use as an organic electrolyte. Since the nonflammable silicon element is contained, the flash point is high, the thermal decomposition temperature is high, and the danger such as firing and inflammation can be avoided when a chemical battery is heated due to an abnormal charge/discharge and a short circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrolyte composition for high energy density chemical cells. In particular, the present invention provides an electrolyte composition comprising an organic solvent comprising an organosilicon compound and an electrochemically active electrolyte;
and a chemical battery comprising the same.

[Conventional technology]

A recently developed high energy density chemical battery consists of an alkali metal material as a negative electrode active material, a transition metal chalcogen compound as a positive electrode active material, and an organic electrolyte as an electrolyte.

Among them, lithium or a lithium-containing alloy is used as the negative electrode, a transition metal chalcogen compound such as manganese dioxide or vanadium pentoxide is used as the positive electrode active material, and lithium perchlorate or hexafluoride is used in an organic solvent such as propylene carbonate or tetrahydrofuran, or a mixed solvent thereof. Chemical batteries that use an organic electrolyte in which an alkali metal salt such as lithium phosphate is dissolved as an electrolyte have the highest energy per unit weight because the lithium negative electrode has the greatest tendency to ionize among all metals and has the lowest specific gravity. It has the characteristic of being. A further important feature of these batteries is that they can be repeatedly discharged and charged. It is a well-known fact that the organic electrolyte used in this chemical battery must exhibit high ionic conductivity so that a large current can be extracted, and must also have low viscosity. Conventionally, as an organic solvent for an electrolytic solution that satisfies this condition, a combination of a high dielectric constant solvent that exhibits high electrolyte solubility and a low viscosity solvent that has low viscosity has often been used. Typical solvents used as high dielectric constant solvents include propylene carbonate, ethylene carbonate, T-butyrolactone, dimethyl sulfoxide, sulfolane, and acetonyl.
Tetrahydrofuran, dimethoxyethane, dioxolane, and the like are known as typical low-viscosity solvents. Electrolytes made using these organic solvents exhibit high ionic conductivity and have a low viscosity, so they have a large ion transfer number, and as a result, they have a large capacitance and can draw a large current. A chemical battery has been realized.

[Problem to be solved by the invention]

However, all of the above organic solvents for electrolytes are carbon,
It is an organic compound consisting of hydrogen and oxygen, and most of them belong to the Fire Service Act, Class 4, Petroleum 1 or Petroleum 2, and both are highly flammable. Among them, ether organic solvents have a high vapor pressure and a particularly low flash point. This may pose a problem in terms of the environment in which the battery is used, and if heat is generated due to electrochemical or chemical reactions that occur during charging, discharging, or malfunctions such as short circuits, there is a possibility of ignition or ignition.

This can be an important safety issue when using batteries, and as mentioned above, the organic solvent for the electrolyte is
It is essentially based on being composed of carbon, hydrogen, and oxygen.

An object of the present invention is to provide an electrolytic solution that has less risk of ignition or ignition, which can cause problems when using a battery, and a chemical battery using the same.

[Means to solve the problem]

To summarize the present invention, the present invention relates to a chemical battery, in which an alkali metal is used as a negative electrode, a solid active material is used as a positive electrode, and an organic electrolyte is used as an electrolyte. An electrolyte is added to an organic solvent containing at least one of a group of organosilicon ether compounds, organosilicon ketone compounds, -organosilicon sulfoxide compounds, organosilicon nitrile compounds, organosilicon amide compounds, and organosilicon imide compounds containing a silicon element therein. It is characterized by using a product obtained by dissolving it.

In order to achieve the above object, an electrolyte solution was used in which an electrolyte was dissolved in an organic solvent containing a group of aqueous organosilicon compounds. Organosilicon compounds are a group of compounds belonging to organometallic compounds, and are characterized by having a high flash point and a high thermal decomposition temperature because they contain a flame-retardant silicon element. Therefore, when these are used as electrolyte solvents,
Even if the chemical battery generates heat due to abnormal charging, discharging, or short circuit, the risk of ignition or ignition can be avoided.

Furthermore, the advantages of using these organosilicon compounds as electrolyte solvents are as follows: First, these electrolyte solvents can be used in place of conventional carbon,
Since the surface tension is lower than that of organic solvents consisting of hydrogen and oxygen, it has good wettability to the negative and positive electrode active materials, and also penetrates into minute gaps between particles, so the contact resistance with the electrode is low. As a result, it has the advantage of being able to obtain large values for both voltage and current, which are important characteristics of chemical batteries. Second, organosilicon compounds contain silicon-oxygen bonds that have greater bond energy than carbon-oxygen bonds, so they are less susceptible to redox reactions, and as a result, organic electrolytes using these solvents are has the advantage that electrochemical decomposition reactions are unlikely to occur at the contact surface with the positive and negative electrodes during charging or discharging, and that it operates stably even when used in high-voltage batteries. Also the third
Organosilicon compounds have the characteristic that their viscosity does not change easily with temperature compared to conventional organic solvents consisting of carbon, hydrogen, and oxygen. That is, the viscosity of conventional organic solvents increases rapidly as the temperature decreases, resulting in a decrease in ionic conductivity at low temperatures and deterioration of battery characteristics. On the other hand, the organosilicon compound according to the present invention has the advantage that the viscosity does not suddenly increase even when the temperature decreases, so that there is no such deterioration in battery characteristics.

As mentioned above, when an organosilicon compound of the - group is used as an electrolyte solvent, in addition to being flame retardant and difficult to catch fire, it has various other features not found in conventional electrolytes.

Although the above features apply to general organosilicon compounds, not all organosilicon compounds can be used as the electrolyte solvent of the present invention. In other words, many organosilicon compounds are generally nonpolar and have low solubility in electrolytes consisting of alkali metal salts.Also, since these organosilicon compounds have a small dielectric constant, the degree of ionic dissociation of the dissolved electrolyte is also small, resulting in ionic conductivity. It has the disadvantage of a low rate. As a result, this causes a fundamental deterioration in battery characteristics such that sufficient current cannot be drawn.

As a result of examining solvents that can solve these problems, the present inventors found that among organosilicon compounds, - group of organosilicon ketone compounds, organosilicon sulfoxide compounds, organosilicon nitrile compounds, organosilicon amide compounds, and organosilicon imides. We have discovered that a compound has properties that can solve these problems. These organosilicon compounds have a relatively large dielectric constant, excellent solubility in electrolytes made of alkali metal salts, and a high degree of ionic dissociation, so they exhibit high ionic conductivity. In addition, organosilicon ether compounds alone do not have sufficient solubility in electrolytes, but when mixed with the above organosilicon compounds, they have the effect of reducing the viscosity of the electrolyte and are more flammable than conventional hydrocarbon ether compounds. The score was high and the flame retardancy increased.

If such organosilicon compounds are represented by chemical structural formulas, the first is an organosilicon ether compound RR0-R2, the second is an organosilicon ketone compound RR0-R2, and the third is an organosilicon sulfoxide. Compound 1 R, -3-R2 The fourth is an organosilicon nitrile compound S+-CN, and the sixth is an organosilicon nitrile compound S+-CN. However, in the formula, R1 and R2 represent either an alkyl group, a halogenated alkyl group, an alkylene group, a silyl group, a silylated alkyl group, a siloxyl group, or a siloxylated alkyl group, and R represents hydrogen or an alkyl group, R
3 represents an alkylene group, and Sl represents a silyl group, a silylated alkyl group, a siloxyl group, or a siloxylated alkyl group. However, R1 and R2 may be the same or different, but neither of them must be an alkyl group, a halogenated alkyl group, or an alkylene group.

The silyl group according to the present invention includes a trimethylsilyl group,
Triethylsilyl group, t-butyldimethylsilyl group, etc. are suitable; as the silylated alkyl group, trimethylsilylmethyl group, trimethylsilylethyl group, t-butyldimethylsilylmethyl group, etc. are suitable; as the siloxyl group, 1.1 -dimethyl-3,3,3-)limethylsiloxysilyl group (abbreviation: disiloxyl group) 1,1
-dimethyl-3,3,5,5゜5-pentamethyldisiloxysilyl group (abbreviation n-)lysiloxyl group) Methyl-
Bis(trimethylsiloxy)silyl group (abbreviation 1so-
1,1-dimethyl-3゜3.3- as the siloxylated alkyl group.
)! J methylsiloxysilylmethyl group and the like are suitable.

Specific examples of these organosilicon compounds include the following.

First, specific examples of organosilicon ether compounds include methyltrimethylsilylmethyl ether, ethylene glycol bis(trimethylsilyl) ether, ethylene glycol bis(trimethylsilylmethyl) ether, 1-
Examples include methoxy-2-trimethylsiloxypropane, tetramethoxysilane, and tetraethoxysilane.

Second, specific examples of organosilicon ketone compounds include methyltrimethylsilylmethylketone, di(trimethylsilylmethyl)ketone, ethyltrimethylsilylketone, and ethyltrimethylsilylmethylketone.

Third, specific examples of organosilicon sulfoxide compounds include methyltrimethylsilylmethylsulfoxide, di(trimethylsilylmethyl)sulfoxide, and ethyltrimethylsilylsulfoxide.

Fourth, specific examples of organosilicon compounds include trimethylsilylacetonitrile, trimethylsilylpropionitrile, and the like.

Fifth, as a specific example of the organosilicon amide compound, trimethylsilylacetamide, N-methyl-N-)! J Methylsilylacetamide, N-methyl-N-(t-butyldimethylsilyl)acetamide, N-methyl-N-trimethylsilyltrifluoroacetamide, N-methyl N
-(t-butyldimethylsilyl)trifluoroacetamide, and the like.

Sixth, as a specific example of an organosilicon imide compound, N-
)limethylsilylsuccinoimide, N-trimethylsilylmethylsuccinoimide, N-)limethylsilylethylsuccinoimide, N-)limethylsilylmethoxymethylsuccinoimide, and the like.

When making an electrolyte using these organosilicon compounds,
Although it is possible to use each solvent alone, 2
A mixture of two or more kinds of solvents may be used. Furthermore, other general organic solvents consisting of carbon, hydrogen, and oxygen may be added to these organosilicon compounds. A supporting electrolyte consisting of an alkali metal salt is dissolved in these solvents alone or in a mixture to obtain an organic electrolyte.
5, LiBF, , LiA1[:1. , Li['F+
CD2, LiNbF, , LiPF6,
LiSbF6, LiAsF5, LiCF3SO3
, LiAsF5SO3, LL (CF3SO2N) 2
, KSCN, KISLiCl, LiBr, etc. can be used.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The invention is not limited to these examples.

Example 1 15 g of molecular sieves 4A, which had been heat-treated in advance at 400° C. for 4 hours, was added to methyltrimethylsilylmethylketone 100, stirred for one day, and then passed through an activated alumina column to thoroughly remove moisture. Dissolve 7.8 g of electrolyte LiAsF6 in 50 d of this electrolyte solvent, and
．． An 8 molar organic electrolyte was prepared. The organic electrolyte thus prepared was again passed through an activated alumina column to thoroughly remove moisture. A chemical cell was fabricated using these organic electrolytes as an electrolyte, lithium foil as a negative electrode, and vanadium pentoxide as a positive electrode. The positive electrode active material contains 95mo
le%V2O5-5mole%P20. A mixture pellet containing 70% by weight of this amorphous material, 25% by weight of acetylene black as a conductive agent, and 5% by weight of Teflon as a binder was used as the positive electrode, and metallic lithium was used as the negative electrode. Further, a coin-type lithium battery was fabricated using a microporous polypropylene sheet as a separator. The electrolyte was compatible with the battery components such as the positive electrode, negative electrode, and separator, and quickly penetrated into the battery.

The results of measuring the impedance of the manufactured battery are shown in Table 1 below along with other examples. Also, using this battery, at room temperature,
A charge/discharge test was conducted in a voltage range of 1.8 V to 3.5 V under a constant current of 1 mA. The discharge starting voltages for the first cycle are shown in Table 1 again.

The battery obtained in this experiment was able to be repeatedly discharged and charged normally.

Examples 2 to 5 Electrolyte solutions were prepared in the same manner as in Example 1 using four types of electrolyte solution solvents: methyltrimethylsilylmethylsulfoxide, trimethylsilylacetonitrile, trimethylsilylacetamide, and N-)limethylsilylmethylsuccinoimide. Using these electrolytes, a lithium battery consisting of a lithium negative electrode, a V205 pellet positive electrode, and a polypropylene separator was produced in the same manner as in Example 1. Table 1 also shows the impedance of the produced battery and the discharge start voltage in the charge/discharge test. The impedance and firing voltage differ slightly depending on the electrolytic solution, but this is due to the difference in electrolytic solubility and degree of ionic dissociation of the electrolytic solvent. However, all of the batteries produced were able to be repeatedly discharged and charged normally.

Example 6 An electrolytic solution solvent was prepared by mixing equal volumes of methyltrimethylsilylmethylketone and methyltrimethylsilylmethylsulfoxide, and the electrolytic solution was prepared in the same manner as in Example 1. Using this electrolyte, a lithium battery consisting of a lithium negative electrode, a V205 pellet positive electrode, and a polypropylene separator was produced in the same manner as in Example 1. Table 1 also shows the impedance of the produced battery and the discharge start voltage in the charge/discharge test. The impedance and firing voltage are slightly different, but this is because the electrolyte solubility of the electrolytic solvent and the degree of ionic dissociation are different. However, the fabricated battery was able to be repeatedly discharged and charged normally.

Example 7 An electrolytic solution solvent was prepared by mixing equal volumes of methyltrimethylsilyl methyl ether and propylene carbonate, and the electrolytic solution was prepared in the same manner as in Example 1. Using this electrolyte, a lithium negative electrode, V
A lithium battery consisting of a 2[15 pellet positive electrode and a polypropylene separator was prepared. Table 1 also shows the impedance of the produced battery and the discharge start voltage in the charge/discharge test. The impedance and firing voltage are slightly different, but this is because the electrolyte solubility of the electrolytic solvent and the degree of ionic dissociation are different. However, the fabricated battery was able to be repeatedly discharged and charged normally.

Table 1 Impedance and discharge start voltage of the batteries produced in Examples a) Value at 40°C b) Value at 55°C [Effects of the invention] As explained above, organosilicon compounds containing silicon element in the molecule The electrolyte prepared by using this as an electrolyte solvent exhibits high ionic conductivity and is inherently flame retardant.

Furthermore, when a chemical battery is made using these electrolytes, the electrolyte quickly wets the battery components, and because the electrical contact resistance is low, this battery has a high electromotive force and a large discharge capacity, and can be charged. It has the advantage of being

Claims (1)

[Claims] 1. An alkali metal is used as a negative electrode, a solid active material is used as a positive electrode,
In an electrochemical cell using an organic electrolyte as an electrolyte, the organic electrolyte may be a group of organosilicon ether compounds, organosilicon ketone compounds, organosilicon sulfoxide compounds, organosilicon nitrile compounds, and organic 1. A chemical cell comprising an electrolyte dissolved in an organic solvent containing at least one of a silicon amide compound and an organic silicon imide compound.