JP3418715B2 - Organic electrolyte secondary battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-energy-density and high-reliability organic electrolyte secondary battery as a power supply for driving electronic equipment or a power supply for holding a memory. Things. 2. Description of the Related Art Along with rapid miniaturization of electronic equipment, a secondary battery which is small, lightweight, has a high energy density and can be repeatedly charged and discharged with respect to a battery as a power source thereof. The demand for development is increasing. As a secondary battery satisfying these requirements, an organic electrolyte secondary battery is most promising. As the positive electrode active material of the organic electrolyte secondary battery, various substances such as titanium disulfide, lithium cobalt composite oxide, spinel type lithium manganese oxide, vanadium pentoxide and molybdenum trioxide have been studied. ing. Among them, lithium cobalt composite oxide (L
iCoO ₂ ) and spinel lithium manganese oxide (Li
Mn ₂ O ₄ ) charges and discharges at a very noble potential of 4 V (Li / Li ⁺ ) or more, so that a battery having a high discharge voltage can be realized by using it as a positive electrode. [0004] As the negative electrode active material of the organic electrolyte secondary battery, various materials such as lithium metal and a Li-Al alloy capable of occluding and releasing lithium and carbon materials have been studied. Has an advantage that a battery having high safety and a long cycle life can be obtained. However, in this type of battery, while lithium having a low potential is used as a negative electrode active material, while a metal oxide having a noble potential is used for a positive electrode, the electrolyte is easily decomposed in each of the negative electrode and the positive electrode. In the situation. Therefore, it is indispensable to adopt a configuration in consideration of these points in selecting an electrolytic solution, and it has been proposed to use various electrolytic solutions. [0006] Most of them are composed of high dielectric constant solvents such as propylene carbonate, ethylene carbonate, γ-butyrolactone and sulfolane as solvents and low viscosity solvents such as 1,2-dimethoxyethane, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate. Are mixed. On the other hand, as the solute, lithium perchlorate,
Lithium trifluoromethanesulfonate, lithium hexafluorophosphate and the like are generally used. In particular, lithium hexafluorophosphate has been widely used in recent years because of its high safety and high ionic conductivity of a dissolved electrolyte. [0008] However, even when the above-described electrolytic solution is used, there is a problem that the battery performance is reduced as the charge / discharge cycle progresses. The present invention is directed to an organic electrolyte secondary battery comprising a negative electrode, a positive electrode, and an organic electrolyte comprising a solvent and a solute. The cyclic dicarbonate compound is added. However,
In Chemical Formula 1, R and R 'are alkylene groups selected from methylene, ethylene, propylene, and butylene. As described above, in this type of battery, the decomposition reaction of the electrolytic solution is apt to occur, and it is considered that this is the main cause of deteriorating the battery performance. However, it has been found that a battery in which a cyclic dicarbonate compound is added to an electrolytic solution can provide a battery having excellent storage characteristics and good cycle characteristics, and has completed the present invention. That is, the cyclic dicarbonate compound is considered to suppress the decomposition reaction of the electrolytic solution. The present invention will be described below with reference to preferred embodiments. However, the present invention is not limited to the following embodiments without departing from the gist of the present invention. The positive electrode is a lithium-cobalt composite oxide (L
iCoO ₂ ), a carbon powder as a conductive agent, and a fluororesin powder as a binder are sufficiently mixed in a weight ratio of 90: 3: 7, and then molded under pressure. The negative electrode is obtained by sufficiently mixing graphite and a fluororesin powder as a binder at a weight ratio of 91: 9 and then press-molding. FIG. 1 is a longitudinal sectional view of a button type battery.
In this figure, 1 is a case also serving as a positive electrode terminal formed by stamping a stainless steel (SUS316) steel plate, and 2 is a stainless steel (S
USU316) A sealing plate also serving as a negative electrode terminal formed by stamping a steel plate, and the negative electrode 3 is in contact with the inner wall thereof. Reference numeral 5 denotes a separator made of polypropylene impregnated with an organic electrolyte, 6 denotes a positive electrode, and the inside of the sealing plate 2 also serving as a negative electrode terminal is caulked by inwardly caulking an open end of the case 1 also serving as a positive electrode terminal. It is hermetically sealed by tightening. The organic electrolyte is prepared by mixing ethylene carbonate and dimethyl carbonate at a volume ratio of 1: 1 and then adding 5 vol% of dimethylene carbonate to an organic solvent containing lithium hexafluorophosphate at a concentration of 1 mol / liter. The dissolved one was used. The battery contains about 1 solution of the above electrolyte.
50 μl was injected. The dimensions of this battery are 20 mm in diameter and 2 mm in height.
It is. The battery thus prepared was designated as the battery of the present invention (A). The battery of the present invention having the same structure as that of this embodiment except that ethylene methylene dicarbonate was used in place of dimethyl methylene dicarbonate in the above embodiment is referred to as (B). Ethyl is used instead of dimethyl carbonate. A battery of the present invention having the same configuration as that of this example except that methyl carbonate was used was designated as (C). For further comparison, a mixture of ethylene carbonate and dimethyl carbonate (volume ratio 1: 1) was used as an organic solvent without adding a cyclic dicarbonate compound.
1) Comparative batteries having the same configuration as the battery of the present invention except that a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio of 1: 1) were used were (A) and (B), respectively. Call. Next, these batteries were charged at a constant current of 2.0 mA in a thermostat at a temperature of 60 ° C. until the terminal voltage reached 4.2 V, followed by a constant current of 2.0 mA. so,
A charge / discharge cycle life test for discharging until the terminal voltage reached 3 V was performed 300 times. FIG. 2 shows a change in the discharge capacity as the charge / discharge cycle of each battery progresses. As is clear from the results shown in FIG. 2, the batteries (A), (B) and (C) of the present invention to which the cyclic dicarbonate compound was added were compared with the comparative batteries (A) and (A). Of the discharge capacity with the progress of the discharge is small. In the above embodiment, the case where dimethylene dicarbonate and ethylene methylene dicarbonate are used as the cyclic dicarbonate compound has been described.
The same effect can be obtained if R and R ′ in Chemical Formula 1 are cyclic dicarbonate compounds in which the alkyl group is selected from methylene, ethylene, propylene, and butylene. Examples include diethylene dicarbonate, ethylene propylene dicarbonate, dipropylene dicarbonate, dibutylene dicarbonate, and the like. Further, in the above-described embodiment, the case where the addition amount of the cyclic dicarbonate compound to the organic solvent is 5 vol% is described, but the addition amount is not particularly limited. The range is preferably 0.1 to 50% by volume, more preferably 1 to 10% by volume. When the addition amount is less than 1 vol%, the effect gradually decreases as the addition amount decreases, and when the addition amount is 10 vol% or more, the ionic conductivity of the electrolytic solution tends to decrease as the addition amount increases. In the above embodiment, the case where a lithium-cobalt composite oxide is used as the positive electrode active material has been described.
Various materials such as lithium nickel composite oxide (LiNiO ₂ ), titanium disulfide, manganese dioxide, spinel type lithium manganese oxide (LiMn ₂ O ₄ ), vanadium pentoxide, and molybdenum trioxide can be used. In the above embodiments, the case where graphite is used for the negative electrode has been described, but the negative electrode is not particularly limited. A similar effect can be obtained when applied to a low-crystalline carbon material, metallic lithium, a lithium alloy, or the like. The organic solvent and solute are not basically limited either. The same effects as those of the present invention can be obtained as long as they are conventionally used for lithium batteries. For example, as a solvent, a low-viscosity solvent such as 1,2-dimethoxyethane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl formate is mixed with a high dielectric constant solvent such as propylene carbonate, ethylene carbonate, γ-butyrolactone, and sulfolane. What was done can be used. Examples of the electrolyte include lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate and lithium trifluoromethanesulfonate.
More than one species can be used. Although the batteries according to the above embodiments are all button batteries, the same effects can be obtained by applying the present invention to cylindrical, square or paper batteries. As described above, in a battery including a negative electrode, a positive electrode, and an organic electrolytic solution comprising a solvent and a solute, by adding a cyclic dicarbonate compound to the solvent,
It can effectively suppress a decrease in the discharge capacity due to the progress of the charge / discharge cycle, which is a problem of this type of battery, and its industrial value is extremely large.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an internal structure of a button-type battery as an example of an organic electrolyte secondary battery. FIG. 2 is a diagram showing a change in discharge capacity as a charge / discharge cycle of a test battery progresses. [Description of Signs] 1 Battery case 2 Sealing plate 3 Negative electrode 4 Gasket 5 Separator 6 Positive electrode

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-282849 (JP, A) JP-A-5-82168 (JP, A) JP-A 1-132059 (JP, A) JP-A-1- 320767 (JP, A) JP-A-1-134873 (JP, A) JP-A-1-134872 (JP, A) JP-A-5-335033 (JP, A) JP-A-7-37612 (JP, A) JP-A-7-165751 (JP, A) JP-A-4-500439 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/40 H01M 6/16

Claims (1)

(57) Claims 1. A negative electrode, a positive electrode, an organic electrolytic solution comprising a solvent and a solute, and the solvent contains a cyclic dicarbonate compound represented by the following chemical formula (1). An organic electrolyte secondary battery, characterized in that: Embedded image Wherein R and R ′ in Chemical Formula 1 are methylene, ethylene,
Pro Pi Ren, an alkylene group selected from butylene.