JPS62150668A - Electrorytic solution composition - Google Patents

Abstract

PURPOSE:To prevent the fall of the characteristics of a cell caused by chemical change at a time of charge or discharge by containing a specific 1,3-dioxolan-2- on derivative and a lithium salt. CONSTITUTION:A 1,3-dioxolan-2-on derivative and a lithium salt shown by the expression are contained. In the expression, R indicates an alkyl group of atomic member 1-4. Among compounds shown by the expression, the especially preferable one is 4-methoxymethyl-1, 3-dioxolan-2-on. The especially preferable one as the lithium salt is lithium perchlorate, or lithium borofluoride, or lithium phosphofluoride. The concentration of the lithium salt is preferably 0.5-2mol/l.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrolyte compositions, particularly electrolyte compositions suitable for lithium batteries.

Conventional technology and lithium batteries have characteristics such as high energy density and high discharge voltage, but due to the high reactivity and discharge voltage of lithium, the electrolyte composition becomes unstable and battery characteristics are impaired. It also has the disadvantage of being exposed. This tendency is particularly remarkable in the case of secondary batteries; for example, the electrolyte composition that has been traditionally used in lithium batteries, in which lithium salt is dissolved in propylene carbonate, undergoes chemical changes during charging and discharging, causing a change in battery characteristics. lower.

The present invention has been made to solve these problems.

Means for solving the problem, that is, the present invention provides a 1,3-dioxolan-2-one derivative represented by the general formula (I): (wherein k represents an alkyl group having 1 to 4 carbon atoms) and an electrolyte composition containing a lithium salt.

In the general formula (I), the term "a" represents a linear or branched alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and the like.

Among the compounds represented by formula (I), 4-methoxymethyl-1,3-dioxolan-2-one is particularly preferred.

The compound represented by the general formula (I) is, for example, 3-alkoxy-1,2-propanediol obtained by the addition reaction of Grindol and a lower alcohol having 1 to 4 carbon atoms, diethyl carbonate, alkyl chloroformate, etc. Alternatively, it can be easily produced by reacting phosgene.

As the lithium salt, any lithium salt conventionally used in organic solvent type lithium batteries can be used in the present invention. Examples of such lithium salts include lithium perchlorate, lithium borofluoride, lithium arsenic fluoride, lithium phosphorus fluoride, lithium halides, and lithium chloroaluminate. Particularly preferred are lithium perchlorate, These are lithium borofluoride and lithium phosphorus fluoride.

The concentration of the lithium salt is usually 0.1 to 3 mol/C1, preferably 0.5 to 2 mol/L.

In addition to the above-mentioned 1,3-dioxolan-2-one derivative and lithium salt, the electrolyte composition according to the present invention may optionally contain other organic solvents used in conventional organic solvent type lithium batteries, such as Ethers such as propylene carbonate, dimethoxyethane, and dimethoxytetrahydrofuran, and esters such as γ-butyrolactone may be appropriately blended within the range in which the intended purpose of the present invention can be achieved. In this case, the amount of 1,3-dioxolan-2-one derivative is usually about 5% by volume or more based on the total amount of organic solvent.

1. A method for obtaining an ionically conductive composition containing a 3-dioxolan-2-one derivative and a lithium salt is as follows:
- Any method may be used as long as it is dissolved in the dioxolan-2-one derivative and other organic solvent as desired,
It is not particularly limited.

The electrolyte composition of the present invention is an electrolyte composition suitable for lithium batteries, and can be used in the same manner as electrolytes used in ordinary organic electrolyte type lithium batteries.

For example, the electrolyte composition of the present invention can be used alone or in the form of being impregnated with a support (woven fabric, nonwoven fabric, film, etc.) by coating, impregnating, or dipping.

A lithium battery can be constructed using the electrolyte composition of the present invention. In this case, components other than the electrolyte composition can be configured in the same manner as usual. For example, this battery has a positive electrode current collector and a negative electrode current collector, uses a positive electrode active material and a negative electrode active material, and contacts the positive electrode active material and the negative electrode active material with the electrolyte composition of the present invention interposed therebetween. It can be configured as follows.

The positive electrode or negative electrode current collector may be a conventional one, such as a conductor such as stainless steel or carbon. The shape may be a net shape, a plate shape, a rod shape, etc., and a net shape is preferable.

Examples of negative electrode active materials include lithium and lithium-based alloys (such as lithium-aluminum alloys).

Its shape includes foil, plate, rod, etc., but foil is preferred.

Transition metal oxides (manganese dioxide,
Examples include vanadium pentoxide, molybdenum oxide, copper oxide, etc.), carbon fluoride, and transition metal chalcogen compounds (iron sulfide, titanium sulfide, etc.). The positive electrode active material is generally produced by pressurizing the above positive electrode active material together with powder of synthetic resin (polyethylene, Teflon, polystyrene, etc.) in a mold, sintering it,
A molded version is used.

An example of a lithium battery using the electrolyte composition of the present invention will be explained with reference to FIG. In the figure, (I) is a positive electrode can (positive electrode current collector), (2) is a metal net for current collection, (3) is a positive electrode active material, (4) is a separator, (5) is a liquid absorbing material, (
6) is an L-shaped gasket, (7) is a negative electrode active material, and (3) is an L-shaped gasket.
) is a negative electrode can, and (9) is a metal net for current collection. A current collecting metal net (2) is placed on the bottom of the positive electrode can (I), and a molded positive electrode active material (3) is pressure-bonded thereon. Next, a porous or mesh-like separator (made of polyethylene, etc.) (4) is placed on the positive electrode active material (3), a synthetic resin absorbent material (5) is placed on the separator (4), and the book is placed on the positive electrode active material (3). After injecting the electrolyte composition of the invention, an L-shaped gasket (
6) is inserted along the wall of the positive electrode can (I). On the other hand, the negative electrode active material (7) is placed in the negative electrode can (8) with a current collecting metal net (9).
), the positive electrode can (I) is placed on a liquid-absorbent material (5) containing and holding the electrolyte composition of the present invention, and the open end of the positive electrode can (I) is bent inward and sealed. do.

The electrolytic solution composition of the present invention has high ionic conductivity and is a stable electrolytic solution with almost no chemical changes during charging and discharging. Lithium secondary batteries and secondary batteries, especially secondary batteries, using this electrolyte have sufficient battery characteristics over a long period of time.

The present invention will be further explained below with reference to Examples, Reference Examples, and Reference Comparative Examples, but the present invention is not limited thereto.

Example 1 Lithium perchlorate was dissolved in 4-methoxymethyl-1,3-dioquinlan-2-one at a ratio of 1 mol/l to obtain an electrolytic solution composition of the present invention.

A molded positive electrode active material prepared by mixing vanadium pentoxide, acetylene black, and polyethylene powder and molding under pressure was pressure-bonded onto a nickel net placed on the bottom of a stainless steel positive electrode can. Next, a polypropylene separator was placed on the molded body, and then the electrolyte composition of the present invention of Example 1 was injected and a gasket was inserted. Thereafter, a stainless steel negative electrode can with lithium foil adhered thereto was placed on a separator, the open end of the positive electrode can was bent inward, and the sealed part was hermetically sealed with glass to produce a battery.

As a reference comparative example, a battery was similarly prepared using propylene carbonate instead of 4-methoxymethyl-1,3-dioxolan-2-one.

Note that both batteries are coin-shaped batteries with dimensions of 2.5H x 23m x φ.

Discharge at a constant current of 1 mA until the depth of discharge reaches 30%,
A charge/discharge test was conducted to charge the battery to that capacity, and the results are shown in Table 1.

Example 2 Lithium borofluoride was dissolved in 4-methoxymethyl-1,3-dioxolan-2-one at a ratio of 0.5 mol/4 to obtain an electrolytic solution composition of the present invention.

A positive electrode made by pressing a positive electrode active material molded body made by mixing mankan dioxide, acetylene black and polyethylene powder and press-molding it onto a stainless steel net, a negative electrode made by adhering lithium foil to a stainless steel net, Each of the electrolyte compositions of the present invention of Example 2 was placed in a glass container and sealed to assemble a battery.

As a reference comparative example, a battery was similarly prepared using propylene carbonate instead of 4-methoxymethyl-1,3-dioxolan-2-one.

Figure 2 shows the voltage characteristics of the battery when charging is performed with a constant current of Q, 5mA. In the figure, ■ indicates the present invention, and ■ indicates a comparative example. Further, FIG. 3 shows the change in internal resistance of the battery when the battery was discharged at a constant current of 15 mA until the depth of discharge reached 16% and then charged to that capacity. In the figure, ■ indicates the present invention, and ■ indicates a comparative example.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a lithium battery using the composition according to the present invention. FIG. 2 is a diagram showing the relationship between charging time and battery voltage. FIG. 3 is a diagram showing the relationship between charging time and number of cycles. (3)... Positive electrode active material, (4)... Separator,
(5)...Liquid absorbing material, (7)...Negative electrode active material. Figure 1 Figure 3 Charging [t-A Runo cycle number ζ times]

Claims (1)

[Claims] 1. General formula (I): ▲There are numerical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R represents an alkyl group having 1 to 4 carbon atoms) 1, An electrolytic solution composition containing a 3-dioxolan-2-one derivative and a lithium salt. 2. The electrolyte composition according to item 1, wherein the compound represented by formula (I) is 4-methoxymethyl-1,3-dioxolan-2-one. 3. The electrolytic solution composition according to item 1, wherein the concentration of the lithium salt is about 0.1 to 3 mol/l.