JPH0665075B2 - Non-aqueous electrolyte battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte battery, and more particularly to a non-aqueous primary or secondary battery using a light metal such as lithium or sodium as a negative electrode active material. is there.

<Prior Art> The above-mentioned non-aqueous electrolyte battery represented by a lithium battery is a lightweight and high energy density battery, and has various types such as a cylindrical spiral type, a cylindrical inside-out type, a coin type or a pin type. The form is widely used. In this type of battery, the above-described negative electrode using a light metal as an active material is combined with a positive electrode using manganese dioxide, fluorocarbon, or the like as an active material, and a non-aqueous organic solvent is used in lithium perchlorate (LiClO ₄ ) A configuration using a non-aqueous electrolytic solution in which an alkali metal salt such as lithium tetrafluoroborate (LiBF ₄ ) or the like is dissolved as an electrolyte is adopted.

The organic solvent used in this non-aqueous electrolytic solution must have high solubility of the alkali metal salt used as the electrolyte and high ionic conductivity, and high dielectric constant and low viscosity, while being wide It must have a low melting point and a high boiling point so that it can be used safely over a temperature range.

In the current non-aqueous electrolyte battery, for example, a lithium battery, mainly from the viewpoint of improving battery performance, propylene carbonate, dimethoxyethane or γ-butyrolactone or a high dielectric constant organic solvent as a solvent used alone or in combination,
A nonaqueous electrolytic solution in which the above lithium perchlorate or the like is dissolved is used.

<Problems to be Solved by the Invention> By the way, in this type of non-aqueous electrolyte battery, the positive electrode and the negative electrode are short-circuited during battery assembly, and even when the battery is assembled, the positive electrode current collector When the body and the negative electrode or the positive electrode lead plate and the negative electrode can are short-circuited, rapid heat generation occurs. In some cases, sparks may occur when such a short circuit occurs between the electrodes. Further, the temperature of the battery is similarly increased by short-circuiting the battery externally after assembly or by heating from the outside when throwing into a fire. In a battery that uses a solvent as the electrolyte as described above, the flash point or ignition point of the solvent is considerably low, so that the electrolyte is apt to ignite or ignite due to the temperature rise, etc. There is a risk of explosion due to the action of lithium chlorate and poor handling. In particular, in the case of a cylindrical spiral battery, the degree of increase in battery temperature due to a large current flowing at the time of short circuit is rapid, and therefore this risk is particularly high and a serious ignition accident is likely to occur.

<Means for Solving Problems> The present inventor, in order to obtain a non-aqueous electrolyte battery having safe and practically sufficient battery performance even when the temperature rises as described above,
After repeatedly studying the organic solvent used for the electrolyte,
The present invention has been completed by knowing that a desired battery can be obtained by using the following means.

That is, the non-aqueous electrolyte battery of the present invention is a non-aqueous electrolyte battery having a negative electrode using a light metal such as lithium and sodium as an active material, a positive electrode, and a non-aqueous electrolyte solution. A high-dielectric-constant organic solvent having a dielectric constant of 30 or more at a temperature of 20 ° C. and a viscosity of 1 cp or more at a temperature of 25 ° C., which is an organic solvent prepared by mixing one or two selected from ethylene carbonate and 3-methyl-2oxazolidone. In a mixed solvent of a low-viscosity organic solvent having a flash point of 30 ° C. or higher, which is made of diethoxyethane, LiCF ₃ SO ₃ , L
iPF _6, LiAsF _6, LiClO ₄ dissolved than at least one an electrolyte selected using one made by, the high dielectric constant organic solvent and the low viscosity organic solvent and at a volume ratio of 2: 1 to 1: 2 The point is that they are mixed in a ratio.

<Operation> The above-mentioned high dielectric constant organic solvent has a high electrolyte solubility and a boiling point of dimethylsulfoxide, which is the lowest among them.
Since dimethylsulfoxide has the lowest flash point of 9 ° C and also has the lowest flash point of 95 ° C, if this is used as the electrolyte solvent, the electrolyte does not easily ignite or ignite during battery assembly or after manufacturing. A high non-aqueous electrolyte battery can be obtained. However, all of these high dielectric constant organic solvents have high viscosities of 1 cp or more, and particularly when used at low temperatures, the conductivity of the electrolytic solution is greatly reduced, which is a major drawback in battery performance. In the present invention, this high dielectric constant organic solvent is mixed with a low-viscosity organic solvent to solve this drawback.
In this case, if the flash point of the low-viscosity organic solvent is low, the safety of the battery is significantly impaired by the mixing of the low-viscosity organic solvent, even though the safety of the high-dielectric constant organic solvent is maintained. Therefore, the flash point of this low-viscosity organic solvent is a temperature at which it does not easily ignite at least at room temperature.
Must be above ℃.

In addition, this type of low-viscosity organic solvent usually has a low solubility of the electrolyte, and if used in large amounts, it is disadvantageous in battery performance. Also, it is not preferable in terms of battery performance. According to the research conducted by the present inventor, the mixing ratio of these two organic solvents (high dielectric constant organic solvent: low viscosity organic solvent) is 2: by volume.
It is preferable to set it in the range of 1 to 1: 2, and it has been known that a battery satisfying both safety and battery performance in practical use can be obtained by setting it in this range.

<Example> The following will describe an example of the present invention.

Ethylene carbonate (EC) and dimethoxyethane (D
A mixed solvent for comparison made by variously changing the mixing ratio with ME) and a mixed solution according to the present invention prepared by mixing ethylene carbonate (EC) with diethoxyethane (DEE) at various mixing ratios were prepared. The flash point (° C) of each of these was determined by the tag method. The results are shown in Table 1 for the mixed solvent for comparison and in Table 2 for the mixed solvent of the present invention.

From these results, it is understood that the mixed solvent according to the present invention does not ignite at around room temperature, and therefore a highly safe non-aqueous electrolyte battery can be produced by using this mixed solvent as the electrolytic solution solvent. .

In addition, when the above-mentioned ethylene carbonate is used as the high dielectric constant organic solvent and 3 methyl-2 oxazolidone, dimethylsulfoxide, or sulfolane is used alone or in combination of two or more, the flash point is 30 ° C. It was possible to obtain a mixed solvent having a high value as above.

When a non-aqueous electrolyte battery is formed by using these mixed solvents, the positive electrode active material includes metal oxides such as MnO ₂ , MoO _{3 and} CuO, metal chlorides such as AgCl ₂ and CuCl ₂ , CuF ₂ and the like. Metal fluoride such as NiF ₂
Alternatively, a metal sulfide such as CuS or Ni ₃ S ₂ can be used, and a light metal such as lithium, sodium, or potassium may be used as the negative electrode active material.

Further, as the electrolyte to be dissolved in the electrolyte solution solvent, LiC
_{F 3 SO 3, LiPF 6,} LiAsF 6, LiClO 4
However, it is needless to say that use of a material other than LiClO ₄ is preferable because a battery with higher safety can be obtained.

On the other hand, the following experiment was conducted in order to investigate the preferable mixing ratio (mixing volume ratio) of the high dielectric constant organic solvent and the low viscosity organic solvent.

First, in a mixed system of ethylene carbonate (high-dielectric-constant organic solvent) and diethoxyethane (low-viscosity organic solvent), prepare a mixed solvent in which the mixing volume ratio is appropriately changed, and dissolve 1 mol / mol of LiClO ₄ as a solute in them. The change in dielectric constant C (ms) at a temperature of 20 ° C. was examined. The results are shown in FIG. 1, and the mixing volume ratio of ethylene carbonate and diethoxyethane was 1: 3 (= 25: 75).
~ 3: 1 (= 75: 25), more preferably 1: 2 (=
When the ratio was within the range of 33:67) to 2: 1 (= 67: 33), a high dielectric constant was exhibited, and a nonaqueous electrolytic solution with good performance was obtained.

Further, in a mixed system of ethylene carbonate (EC) and dietoxyethane, the mixing volume ratio (EC: diethoxyethane) is 1: 2 (Battery A), 1: 1 (Battery B), 1: 3.
(Battery C): 3: 1 (Battery D) was prepared as a mixed solvent, and 1 mol of LiCF ₃ SO ₃ was added to each of them as a solute.
/ CR2025 type button batteries (Batteries A to D) were produced using the dissolved non-aqueous electrolyte. These batteries A to D
Was continuously discharged at a temperature of 20 ° C. with a resistance of 6.5 kΩ, and the change with time of the terminal voltage (V) of each battery at that time was examined. The results are shown in FIG. 2, and each battery showed good characteristics.

Further, the battery type using the mixed solvent of the present invention is not particularly limited, and may be a coin type, a cylindrical spiral type, a cylindrical inside-out type, a pin type, or the like, but a cylindrical spiral type is particularly preferable. If it is applied to a battery, a great effect can be obtained, and the safety of the battery at the time of a short circuit is greatly improved.

<Effects of the Invention> As described above, according to the present invention, it is possible to improve battery safety and facilitate handling while maintaining practically sufficient battery performance.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the mixed volume ratio of the solvent in the non-aqueous electrolytic solution and the conductivity, and FIG. 2 is a graph showing the characteristics of each battery of the example.

Front Page Continuation (72) Inventor Masakazu Kitakata, No. 36-11 Shimbashi, Minato-ku, Tokyo, Fuji Electric Chemical Co., Ltd. (56) References JP 63-259976 (JP, A) JP 60- 154478 (JP, A)

Claims (1)

[Claims] 1. A non-aqueous electrolyte battery having a negative electrode using a light metal such as lithium and sodium as an active material, a positive electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is ethylene carbonate, 3-methyl-2. An organic solvent prepared by mixing one or two kinds selected from oxazolidones and having a dielectric constant of 3 at a temperature of 20 ° C.
A high dielectric constant organic solvent having a viscosity of 1 cp or more at a temperature of 0 or more and a temperature of 25 ° C., and a flash point of 3 are diethoxyethane.
LiCF _{3 in} a mixed solvent with a low-viscosity organic solvent at 0 ° C. or higher
A solvent obtained by dissolving an electrolyte made of at least one selected from SO ₃ , LiPF ₆ , LiAsF ₆ , and LiCO ₄ is used, and the high dielectric constant organic solvent and the low viscosity organic solvent are used in a volume ratio of 2: 1 to 1: 1. : A non-aqueous electrolyte battery mixed in a ratio of 2: