JP2000251935A - Organic electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make mounting using a reflow process possible without deterioration of battery characteristics even when the battery is exposed to a high temperature by preparing an organic electrolyte with a solvent containing methyl oxazolidinone and a solute containing a lithium salt having a sulfone group as the min component. SOLUTION: As the solvent used in the organic electrolyte of an organic electrolyte battery, a mixed organic solvent of methyl oxazolidinone and at least one solvent selected from the group comprising sulfolane, 3-methylsulfolane, and tetraglyme is preferable. As the lithium salt having a sulfonic acid group used in the solute, lithium trifluoromathanesulfonate(LiCF3SO3) is preferable, and in addition lithium bisperfluoromethylsulfonyl imide containing imide bonding in a structure or lithium bisperfluoroethylsulfonyl imide is listed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electrolyte battery used for a main power supply of an electronic device and a power supply for memory backup, and by providing high temperature heat resistance to a power generation element and a housing member, to improve reliability during high temperature storage. Together with
The present invention relates to an organic electrolyte battery that can be mounted on a substrate by automatic soldering using a reflow method.

[0002]

2. Description of the Related Art In general, an organic electrolyte battery using lithium or an alloy thereof for a negative electrode has a high energy density, is capable of reducing the size and weight of equipment, and has high reliability such as storage characteristics and leakage resistance. Due to its excellent performance, its demand as a main power supply for various electronic devices and a power supply for memory backup is increasing year by year. In this type of battery, a primary battery that cannot be charged is predominant, but as a rechargeable secondary battery, a battery in which a negative electrode is composed of a lithium aluminum alloy or the like, and a positive electrode is a combination of vanadium pentoxide and lithium manganate, respectively is known. In recent years, a coin-type organic electrolyte battery in which these power generation elements are housed in a flat battery container has been put to practical use.

[0003] A coin-type organic electrolyte battery is suitably used as a memory backup power supply for a small portable device, and in particular, recently, a battery having a battery diameter set to 6 mm or less has been actively developed. When such a battery is mounted on a circuit board, both the battery and the circuit board are miniaturized. Therefore, when a manual mounting method is employed, the number of steps is greatly increased. Therefore, as an efficient mounting method, an attempt has been made to mount a battery on a circuit board by automatic soldering using a reflow method.

[0004]

Mounting on a circuit board by the reflow method is performed by passing a battery through the inside of a reflow furnace. The inside of the reflow furnace is in a high temperature state for a short period of time, and particularly in a peak time of about several tens of seconds, is in an ultra-high temperature state reaching 250 ° C. In the organic electrolyte battery used for such an application, each component is required to have heat resistance. For example, as a characteristic required for an organic electrolyte, a necessary condition is that the boiling point of the solvent is 250 ° C. or higher.

However, in the organic electrolyte batteries currently used for general purposes, propylene carbonate and ethylene carbonate are mainly used as a solvent for the organic electrolyte, and the boiling points of these are all 250 ° C. or less. . When such an organic electrolyte battery is passed through a reflow furnace, the electrolyte inside the battery container is instantaneously vaporized. At this time, the pressure inside the container rapidly increases, and the fitting portion of the battery container may be loosened, thereby causing a problem such as leakage of the electrolyte.

[0006] Further, it is necessary that the solvent lowers the viscosity of the solvent to increase the mobility of lithium ions so that the discharge reaction of the battery proceeds smoothly. Therefore, low-viscosity solvents such as diethylene carbonate, 1,2-dimethoxyethane, and 1,2-diethoxyethane are often added.
However, since these solvents have a low boiling point of about 100 ° C., the boiling point of the electrolytic solution is lowered in the reflow furnace, and the pressure inside the battery container is increased due to a rapid temperature rise.

[0007] On the other hand, lithium perchlorate, lithium phosphorus hexafluoride, and the like are used as a lithium salt applied to a solute of an organic electrolytic solution.
It is around 00 ° C. If the lithium salt is exposed to a high temperature exceeding 100 ° C. for a moment even inside the reflow furnace, the lithium salt is thermally decomposed, its function is lost, and a normal battery reaction cannot be performed.

[0008] Further, the heat resistance of each component constituting the organic electrolyte battery is also important. Generally, polypropylene is used for both a gasket for insulating a positive electrode can and a negative electrode can and a separator for insulating a positive electrode and a negative electrode. Thermal softening temperature of polypropylene is from 100 ° C to 120
° C and the gaskets and separators are exposed to temperatures significantly higher than the thermal softening temperature as they pass through the reflow furnace, and are thermally damaged. Due to the damage generated in the separator, insulation between the positive electrode and the negative electrode is reduced, which causes an internal short circuit. In addition, due to the damage caused by the gasket, the degree of sealing of the battery container is reduced, which may cause liquid leakage.

[0009] An organic electrolyte battery is known in which the components of the battery are provided with heat resistance against various problems that occur when the battery is exposed to a high temperature environment as described above (for example, No. 8-322287). This organic electrolyte battery is an organic electrolyte in which a lithium salt is dissolved as a solute in an organic solvent having a boiling point of at least 170 ° C., a separator made of a porous synthetic resin sheet having a boiling point of 170 ° C. or more, and a continuous use temperature of A thermoplastic synthetic resin having a temperature of at least 150 ° C. is used, and as a specific example, a solvent mainly containing γ-butyrolactone is used,
Using an organic electrolyte with lithium borofluoride as a solute,
The use of a resin such as polyphenylene sulfide for the separator and the gasket is disclosed in the above publication.

However, this organic electrolyte battery has the following problems.
An object of the present invention is to provide an organic electrolyte battery that can be used or stored for a long time in a high temperature environment exceeding 50 ° C. And the same problems as the conventional example such as rapid vaporization of the organic solvent, decomposition of the solute, and damage to the gasket and the separator occur.

[0011] As described above, the organic electrolyte battery does not have a high temperature resistance characteristic that does not cause a problem even in a reflow furnace reaching 250 ° C, is compatible with automatic soldering, and is mounted on a circuit board using a reflow method. A mountable organic electrolyte battery has not yet been put to practical use.

[0012]

SUMMARY OF THE INVENTION The present invention provides a power generation element and a battery housing with high temperature resistance in consideration of various conditions inside a reflow furnace when mounting on a circuit board by automatic soldering. By giving, even when exposed to a high temperature of about 250 ° C., the battery characteristics do not deteriorate,
Accordingly, an object of the present invention is to provide an organic electrolyte battery that can be mounted using a reflow method.

In order to achieve the above object, an organic electrolyte battery according to the present invention comprises a power generation element comprising a positive electrode, a negative electrode, a separator and an organic electrolyte in a housing member comprising a positive electrode can, a negative electrode can and a gasket. The organic electrolyte solution has a configuration in which the organic electrolyte solution contains a solvent containing methyl oxazolidinone and a solute mainly containing a lithium salt having a sulfone group.

Here, as the solvent used for the organic electrolyte, a solvent mainly composed of methyl oxazolidinone, or methyl oxazolidinone and sulfolane,
A mixed organic solvent obtained by mixing at least one organic solvent selected from the group consisting of 3-methylsulfolane and tetraglyme is preferable.

The lithium salt having a sulfone group used for the solute is preferably lithium trifluoromethane (LiCF ₃ SO ₃ ). Further, lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) having an imide bond in the structure or lithium bisperfluoroethylsulfonylimide LiN (C ₂ F ₅ SO ₂ ) ₂ can be given.

Further, a nonwoven fabric or cellulose paper made of polyphenylene sulfide PPS is used as a separator interposed between the positive electrode and the negative electrode, and a polyphenylene sulfide PPS is similarly used as a gasket for insulating the positive electrode can and the negative electrode can.

According to this configuration, heat resistance can be imparted to the organic electrolyte battery, and the battery characteristics are not adversely affected even when exposed to a high temperature environment of about 250 ° C.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

The invention according to claims 1 to 5 is directed to an organic electrolyte battery in which a power generating element comprising a positive electrode, a negative electrode, a separator and an organic electrolyte is housed in a housing member having a positive electrode can, a negative electrode can and a gasket. Further, an organic solvent mainly composed of an organic solvent containing methyloxazolidinone and a solute mainly containing a lithium salt having a sulfone group are used.

The boiling point of methyl oxazolidinone is 270
° C, which is higher than the temperature inside the reflow furnace. From this fact, in the temperature range around 250 ° C., methyloxazolidinone has a relatively high vapor pressure, but is in a relatively stable state. Furthermore, because the lithium salt is dissolved as a solute, in the organic electrolyte battery according to the present invention mainly composed of methyl oxazolidinone, the boiling point is further increased by a molar boiling point higher than the boiling point of methyl oxazolidinone alone, It functions effectively in a high-temperature environment.

In addition to the characteristics for the high-temperature environment as described above, a requirement for the organic electrolyte battery includes securing discharge characteristics in a low-temperature environment. here,
An organic electrolytic solution using a solvent containing methyl oxazolidinone as a main component has good characteristics in a high temperature range and also has good characteristics in a low temperature range. Generally, a solvent having a high boiling point tends to have a high melting point and a high viscosity. For this reason, when the conductivity of the electrolyte in the low temperature region is low, for example, when the temperature is lowered to −20 ° C., lithium ions in the organic electrolyte cannot be effectively moved, and almost no discharge capacity can be obtained. Become.

On the other hand, although methyl oxazolidinone has a high boiling point of 270 ° C., its melting point is as low as −15 ° C., and the temperature range existing as a solution is about 2 ° C.
It is characteristic that it is as wide as 80 ° C. Further, the dielectric constant of methyl oxazolidinone is as high as 78, which is equivalent to that of ethylene carbonate or propylene carbonate usually used as a main solvent. Therefore, the lithium salt of the solute can be sufficiently dissolved, and the organic electrolyte solution can maintain the conductivity even in an environment of −20 ° C. due to such characteristics. Further, the movement of the lithium salt during the discharge reaction becomes smooth, and a discharge capacity of 50% or more of the predetermined capacity can be obtained in a wide temperature range, for example, a wide temperature range from -20 ° C to 250 ° C.

Japanese Patent Application Laid-Open No. Sho 62-44961 is known as a prior example which discloses the use of methyloxazolidinone having the above-mentioned properties as a solvent for an organic electrolyte. This publication describes that methyloxazolidinone is used as a solvent having a high dielectric constant and a viscosity required for an electrolyte for the purpose of improving the charging and discharging efficiency of a lithium secondary battery. That is, attention is paid to the dielectric constant and viscosity of methyl oxazolidinone, and this is used as a solvent. On the other hand, the present invention focuses on the characteristics of methyl oxazolidinone in a high-temperature environment for the purpose of imparting high-temperature resistance to a battery,
This was used as a solvent. However, the present invention can be achieved not only by using a solvent having excellent desired properties, but also a solute combined with the solvent of the organic electrolyte.

Therefore, a lithium salt having a sulfone group in the structure was used as the solute dissolved in the solvent containing methyl oxazolidinone according to the present invention. It is necessary to consider the thermal decomposition temperature of the lithium salt and the conductivity of the electrolyte as characteristics of the lithium salt constituting the organic electrolyte applied to the battery for the purpose of imparting high temperature resistance.

The lithium salt having a sulfone group has a high thermal decomposition temperature, and particularly, the thermal decomposition temperature of lithium bisperfluoromethylsulfonylimide or lithium bisperfluoroethylsulfonylimide greatly exceeds 200 ° C .; It is stable even when left in the warm. On the other hand, lithium perchlorate and lithium phosphorus hexafluoride used in conventional organic electrolyte batteries have low thermal decomposition temperatures and lose their function as lithium salts. As described above, the organic electrolyte using the lithium salt having a sulfone group as a solute enables a smooth battery reaction to proceed even in a high-temperature environment.

The lithium salt having a sulfone group is
Affects the conductivity of the electrolyte. The higher the conductivity of the electrolyte, the better. This is one of the important factors that enable the battery to discharge a large current. Conventionally, the solvent of the organic electrolyte is
A low-viscosity solvent such as diethylene carbonate, 1,2-dimethoxyethane, or 1,2-diethoxyethane is blended to lower the viscosity to increase the mobility of lithium ions and to smoothly advance the discharge reaction of the battery. It is common. However, since these solvents have a low boiling point of about 100 ° C., they lower the boiling point of the electrolytic solution, and are not suitable for batteries intended to impart high-temperature resistance. On the other hand, a lithium salt having a sulfone group exhibits high electrical conductivity when dissolved in a solvent. For this reason, a relatively high electrical conductivity can be obtained without the addition of a low-viscosity solvent. In particular, lithium bisperfluoromethylsulfonimide or lithium bisperfluoroethylsulfonylimide having an imide bond in the molecular structure has a high dissociation salt mobility and can realize a smooth discharge reaction.

Further, when this organic electrolyte solution in which a lithium salt having an imide bond is present in the molecular structure is applied to an organic electrolyte battery using a lithium aluminum alloy and having a negative electrode in which lithium is occluded electrochemically. In addition, due to the high conductivity of the organic electrolyte, lithium diffusion on the aluminum alloy surface during lithium electrodeposition becomes smooth, and charge / discharge cycle characteristics are dramatically improved.

In the present embodiment, methyl oxazolidinone is used as the main component of the solvent, and another solvent may be mixed. However, it is preferable to use a single solvent composed of only methyl oxazolidinone. A battery using an organic electrolytic solution composed of a single solvent of methyl oxazolidinone has the best discharge characteristics.

As described above, by using an organic solvent mainly composed of methyl oxazolidinone and an organic solvent having a sulfone group and preferably having a lithium salt having an imide bond in the molecular structure as a solute, high temperature resistance can be obtained. It is possible to obtain an organic electrolyte secondary battery in which the temperature is dramatically improved.

Next, a sixth aspect of the present invention is an organic electrolysis apparatus in which a power generating element comprising a positive electrode, a negative electrode, a separator and an organic electrolyte is housed in a housing member having a positive electrode can, a negative electrode can and a gasket. A liquid battery, comprising: an organic solvent comprising a mixed solvent obtained by mixing at least one kind of sulfolane, 3-methylsulfolane, and tetraglyme with methyloxazolidinone; and an organic electrolyte comprising a solute mainly containing a lithium salt having a sulfone group. Is used.

The organic electrolyte using sulfolane, 3-methylsulfolane, and tetraglyme has lower reactivity with respect to the positive electrode and the negative electrode than the organic electrolyte using only methyloxazolidinone. Is excellent in overcharging characteristics from the viewpoint that hardly occurs and that the potential window of the electrolyte is wider than that of the organic electrolyte using only methyloxazolidinone.

The inventors of the present invention have proposed a solvent mixture of 3-methylsulfolane and sulfolane, or tetraglyme, sulfolane,
-A battery using an organic electrolyte composed of a mixed solvent composed of -methylsulfolane and a solute mainly composed of a lithium salt having a sulfone group was proposed (Japanese Patent Application No. 10-2172).
No. 66). The boiling point of the sulfolane used as the solvent is about 28
7 ° C., and the boiling point of 3-methylsulfolane is about 2
Since the boiling point of 75 ° C. and tetraglyme is about 275 ° C., it is higher than the temperature inside the reflow furnace, and has stable characteristics even in a high-temperature atmosphere when passing through the reflow furnace. Therefore, the organic electrolyte composed of a mixed solvent obtained by combining these solvents and methyloxazolidinone does not cause decomposition of the solvent even in a high-temperature environment.

On the other hand, the freezing points of sulfolane and 3-methylsulfolane are 28 ° C. and 6 ° C., respectively. When these solvents are used as the organic electrolyte, the freezing point is lowered by the lithium salt as a solute, and the freezing temperature can be moved to a lower temperature side. However, when the battery is used at a lower temperature, for example, in a temperature environment of −20 ° C. or less, a battery using a solvent in which tetraglyme is added to sulfolane or 3-methylsulfolane having improved characteristics in a low temperature region is used. Even so, the conductivity in a low temperature range is low, and the discharge characteristics are significantly deteriorated.

Therefore, an organic electrolyte battery according to a sixth aspect of the present invention provides a solute with an increase in the dielectric constant of an electrolyte by adding methyloxazolidinone to a solvent mainly comprising sulfolane, 3-methylsulfolane and tetraglyme. The improvement in the low-temperature characteristics is recognized by the improvement in the solubility of, and the improvement in the liquid absorbing property of the positive electrode accompanying the decrease in the viscosity of the electrolyte. In particular, by adding methyl oxazolidinone in an amount of 5% or more, it is possible to maintain the discharge capacity at 25 ° C. at 40% or more even when discharging at −20 ° C. Improvements are possible.

In the above structure, the volume fraction of methyloxazolidinone in the solvent to which sulfolane, 3-methylsulfolane and tetraglyme are added is 5 to 90%.
Is preferable. When the volume fraction of methyl oxazolidinone exceeds 90%, the capacity deterioration rate during continuous charging rapidly increases, and the effect obtained by the addition of sulfolane, 3-methylsulfolane, and tetraglyme, that is, the effect on the overcharge resistance, is reduced. Give it. However, regarding high temperature resistance properties, sulfolane, 3-methylsulfolane,
The effect of the mixing ratio of methyl oxazolidinone to a mixed solvent in which at least one kind of tetraglyme is mixed is small.

According to the twelfth and thirteenth aspects of the present invention, a power generating element comprising a positive electrode, a negative electrode, a separator and an organic electrolyte is housed in a housing member provided with a positive electrode can, a negative electrode can and a gasket. A battery using an organic solvent containing methyl oxazolidinone and a solute mainly containing a lithium salt having a sulfone group, wherein polyphenylene sulfide is used as a material constituting a gasket and / or a separator. It is a feature.

The gasket also has a function as an insulating packing for insulating the positive electrode can and the negative electrode can, and is manufactured by injection molding into a shape along the inner peripheral surface between the positive electrodes.
Further, the separator is formed of a nonwoven fabric made of polyphenylene sulfide, and a paper separator made of cellulose may be used instead.

The polyphenylene sulfide used for the separator and the gasket of the present invention has been found from the viewpoint of stability against an electrolytic solution in addition to heat resistance. Polyphenylene sulfide has a heat softening temperature of 200 ° C. or higher, and is 25% by adding a filler such as glass fiber.
There is no thermal deformation even at a high temperature of about 0 ° C. For this reason, it is possible to keep maintaining the respective functions as the gasket and the separator even under a high temperature environment inside the reflow furnace. The same can be said for cellulose.

Polyphenylene sulfide and cellulose are methyl oxazolidinone, sulfolane, 3-methyl sulfolane,
It does not dissolve in each solvent of tetraglyme and has the property of being chemically stable. This characteristic has made it possible to obtain long-term reliability.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings for understanding.

(Example 1) FIG. 1 is a sectional view of an organic electrolyte secondary battery according to the present example. The dimensions of the battery are 6.8 mm in diameter and 2.1 mm in thickness. In FIG. 1, a positive electrode can 1 also serving as a positive electrode terminal is made of stainless steel having excellent corrosion resistance, and a negative electrode can 2 also serving as a negative electrode terminal is also made of stainless steel of the same material as the positive electrode can 1. Positive electrode can 1 and negative electrode can 2
Is insulated by a gasket 3 made of polyphenylene sulfide, and a pitch is applied to a surface in contact with the gasket 3 and the positive electrode can 1 and the negative electrode can 2. The positive electrode 4 was prepared by mixing lithium manganate as an active material, carbon black as a conductive agent, and a fluororesin powder as a binder, and molding this into a pellet having a diameter of 4 mm and a thickness of 1.2 mm. It was dried at 250 ° C. for 12 hours. The negative electrode 5 is obtained by punching an aluminum-manganese alloy containing 5% by weight of manganese metal into a disk having a diameter of 4 mm and a thickness of 0.3 mm, and pressing the inner surface of the negative electrode can 2 into an alloy with lithium. To form an alloy of aluminum-manganese alloy and lithium, a lithium foil is pressed against the surface of the aluminum alloy when assembling the battery, and lithium is occluded in the aluminum alloy in the presence of an electrolyte to electrochemically form the lithium-aluminum alloy. And this is used as a negative electrode. A separator 6 made of a nonwoven fabric made of polyphenylene sulfide was disposed between the positive electrode 4 and the negative electrode 5.

In the organic electrolytic solution, methyloxazolidinone was used as a solvent, and lithium bisperfluoromethylsulfonylimide used as a lithium salt was added at 1 mol / l.
What was melt | dissolved by the ratio of was used. This is transferred to a battery container composed of the positive electrode can 1, the negative electrode can 2, and the gasket 3
Filling was performed to prepare a flat organic electrolyte battery.
The obtained battery is referred to as Battery A of the present invention.

Instead of the organic electrolyte in the battery A, lithium trifluoromethaneate was used as a solute lithium salt, and this was added to a solvent, methyl oxazolidinone, for 1 mol.
A battery B having the same configuration as the battery A in other configurations was prepared using an organic electrolyte solution dissolved at a 1 / l ratio.

Instead of the organic electrolytic solution in the battery A, a mixed solvent in which methyloxazolidinone and sulfolane were mixed so that the volume fractions became 65% and 35%, respectively, was used as the solvent, and lithium bisperfluoromethylsulfonylimide was used. Was used at a ratio of 1 mol / l, and a battery C having the same other configuration as the battery A was prepared.

Similarly, instead of the organic electrolytic solution in the battery A, methyl oxazolidinone, sulfolane and tetraglyme were used as solvents in a volume fraction of 65%, 25% and 10%, respectively.
%, Using an organic electrolyte solution in which lithium bisperfluoromethylsulfonylimide was dissolved at a ratio of 1 mol / l, and using the same solvent as the battery A except that the battery D was prepared. did.

Next, a battery E was prepared in the same manner as the battery A, except that a paper separator made of cellulose was used in place of the separator made of the nonwoven fabric made of polyphenylene sulfide in the battery A.

On the other hand, as a comparative example, a solute composed of lithium bisperfluoromethylsulfonylimide was dissolved in a solvent composed of propylene carbonate at a ratio of 1 mol / l in a solvent composed of propylene carbonate in place of the organic electrolyte solution in Battery A. A battery equivalent to battery A is referred to as comparative product F.

Further, instead of the organic electrolytic solution in the battery A, methyl oxazolidinone was used as a solvent, and lithium phosphorus hexafluoride was added as a lithium salt at 1 mol / l.
And a comparative product G having the same structure as that of the battery A in other respects. A comparative product H is a battery in which a separator made of polypropylene is used instead of the separator in the battery A, and the other configuration is the same as the battery A. Further, a comparative gasket is used in which a gasket made of polypropylene is used instead of the gasket of the battery A, and the other configuration is the same as the battery A.

Batteries A to A made according to Embodiment 1
Table 1 shows the configurations of E and comparative products F to I.

[0050]

[Table 1]

After confirming the initial internal resistance (AC method 1 kHz) of each battery shown in (Table 1),
A load of Ω was connected, and the discharge capacity was measured. The discharge capacity was 1 theoretical capacity of the organic electrolyte battery in Example 1.
00 and expressed by the ratio of the measured discharge capacity to this. In addition, the obtained batteries A to E and comparative products F to
A charge / discharge cycle test was also performed for each of I.
The test conditions were as follows: charge end voltage was 3.25 V, discharge end voltage was 2.0 V, charge / discharge was repeated with a constant current of 0.1 mA, and the number of charge / discharge times was determined.

Further, as an evaluation on high temperature resistance characteristics,
A pass test of a reflow furnace that passes through the inside of a high-frequency heating type reflow furnace was performed. The high temperature resistance characteristics of the batteries A to E and the comparative products F to I were examined. The temperature profile of the reflow furnace was maintained at 180 ° C. for 2 minutes as a preheating step, and subsequently at 180 ° C., 245 ° C., and 180 ° C. as a heating step.
Each was passed for 30 seconds in a temperature environment of ° C. Thereafter, the battery was sufficiently cooled by natural cooling until it reached room temperature, and then a visual inspection and a voltage inspection were performed based on the appearance. After the internal resistance was re-measured for the battery in which no problem occurred, the battery was passed through a reflow furnace with the same temperature profile as described above, and inspected and measured. This is 3
After repeating the number of times, the degree of deterioration was confirmed as compared with the initial state. (Table 2) shows the results.

[0053]

[Table 2]

According to Table 2, the discharge capacity of the battery A is 90% of the theoretical value. Further, in the reflow oven pass test, no abnormality is observed up to 3 pass times. Also, since the internal resistance after passing hardly changes from the initial state,
Good results were obtained without any thermal damage due to passage through the reflow furnace. Next, the battery B using lithium trifluoromethane oxide as a lithium salt has a higher initial internal resistance value than the battery A. However, as in the case of the battery A, no abnormality was observed up to three times in the reflow oven, and good results were obtained in terms of electrical characteristics.

In the battery C, since the mixed solvent in which the sulfolane was mixed at a ratio of 35% was used, the viscosity of the electrolytic solution was increased, and the initial internal resistance was high. However, a better result was obtained in comparison with the battery A in the discharge capacity and the charge / discharge cycle, and no abnormality was observed even after passing through the reflow furnace three times. In addition, the battery D to which sulfolane and tetraglyme were added had further improved electrical characteristics in terms of battery electrical characteristics.

On the other hand, the battery E had a higher initial internal resistance value than the battery A due to the use of a paper separator made of cellulose. However, other good results were similarly obtained. Was done.

In contrast to these results, in comparative product F, propylene carbonate used as a solvent boiled while passing through the reflow furnace, and rupture occurred due to an increase in internal pressure due to the boiling. In Comparative product G, lithium phosphorus hexafluoride used as the lithium salt was similarly thermally decomposed during passage through the reflow furnace, and the resistance of the electrolyte increased. This results in an increase in the internal resistance, indicating that the electrical characteristics of the battery have been destroyed.

In the comparative product H, shrinkage of the separator was observed, and an internal short circuit occurred. This is because the polypropylene used as the separator was exposed to a temperature exceeding the melting temperature when passing through the reflow furnace, so that the separator was melted and shrunk, and the positive electrode and the negative electrode came into contact. In Comparative product I, liquid leakage was observed from a gasket using polypropylene. This is because the gasket melted and shrunk due to the same phenomenon as the comparative product H, and liquid leakage occurred from this portion.

Regarding the number of charge / discharge cycles, almost 80 or more charge / discharge cycles are possible in an electrolytic solution using lithium bisperfluoromethylsulfonylimide as a lithium salt, regardless of the type of solvent. Good results were confirmed as compared with the salt, which is considered to have produced a good effect on the form of lithium precipitation on the surface of the lithium aluminum alloy of the negative electrode.

As described above, the battery A in the present embodiment 1
Excellent results were found in all of the discharge performance, charge / discharge cycle performance, and high temperature resistance during reflow. This is due to the heat resistance of methyloxazolidinone, which is the solvent main component of the electrolytic solution, and the heat resistance of lithium bisperfluoromethylsulfonylimide, which is a lithium salt, excellent conductivity, and stability to the lithium aluminum alloy negative electrode. This is because it is possible to obtain heat resistance during reflow by using polyphenylene sulfide PPS for a battery component and a gasket and using a nonwoven fabric of polyphenylene sulfide PPS for a separator. Also, when lithium bisperfluoroethylsulfonylimide is used as the lithium salt, or when 3-methylsulfolane is used as the mixed solvent component, the same result as described above can be obtained.

Example 2 In Example 2, a solvent in which the mixing ratio of methyloxazolidinone and sulfolane was variously changed was used, and lithium bisperfluoromethylsulfonylimide was used as a solute in each solvent at a ratio of 1 mol / l. A dissolved organic electrolyte was obtained. Using these organic electrolytes, a battery J having the structure shown in FIG.
To Q were prepared. The positive electrode is lithium manganate,
A lithium-aluminum alloy was used for the negative electrode, and polyphenylene sulfide was used for the gasket and the separator. Table 3 shows the mixing ratio of methyloxazolidinone and sulfolane in the organic electrolytes of these batteries.

[0062]

[Table 3]

In order to evaluate the high temperature resistance characteristics of these batteries J to Q, a test was performed in which the batteries J to Q were passed through a reflow furnace. The test method was performed by passing through a reflow furnace twice with the same temperature profile as in Example 1. After the test, the occurrence of rupture and liquid leakage was visually confirmed.
No leakage, rupture or the like was observed for all of the batteries.

Further, using the battery after the reflow furnace passage test, the battery was subjected to a temperature of -20 ° C. for 30 minutes.
A discharge test was performed by connecting to a resistance of 0 kΩ. Similarly, using the battery used in the reflow furnace passage test,
3.3V from external circuit to each battery in constant temperature bath
After being left for 40 days with a voltage of
A discharge test was performed by connecting to a 1 kΩ resistor. Based on the measurement of the discharge capacity obtained by these discharge tests,
The ratio to the theoretical capacity was determined in the same manner as in Example 1, and this is shown in (Table 4). Furthermore, the deterioration rate at the time of continuous charging was determined from the discharge capacity at the initial stage of storage in the reflow furnace passage test and the discharge capacity after continuous overcharge at high temperature. The results are also shown in (Table 4).

[0065]

[Table 4]

From Table 4, it can be seen that the battery J uses only sulfolane as a solvent, and the discharge capacity is greatly reduced in a temperature environment of −20 ° C. This is considered to be due to solidification of the electrolytic solution. On the other hand, regarding the batteries K to Q containing methyl oxazolidinone, the discharge capacity in a low-temperature environment increased with an increase in the ratio of methyl oxazolidinone in the solvent. In particular, the battery Q using methyloxazolidinone alone as a solvent can obtain the best results in terms of discharge capacity under this temperature environment.

From a comparison of the discharge capacity at a low temperature, when a solvent consisting of sulfolane alone is used, the electrolytic solution solidifies at −20 ° C. However, when the solvent contains methyl oxazolidinone, the electrolytic solution is solidified. Coagulation is suppressed and a discharge capacity can be secured in a low-temperature environment. At this time, methyl oxazolidinone is also considered to have the effect of improving the conductivity of the electrolytic solution itself.

On the other hand, judging from the viewpoint of continuous overcharge characteristics, a battery J using only sulfolane is preferable. In the battery Q using the solvent consisting of only methyl oxazolidinone, the capacity deterioration rate showed a high value of 70% or more. This increase in the discharge capacity deterioration rate shows a difference when the volume fraction of methyl oxazolidinone in the solvent is 90%, and the batteries P and Q in which the ratio of methyl oxazolidinone is high rapidly deteriorate the discharge capacity deterioration rate. I have. On the other hand, in batteries J to N in which the volume fraction of methyloxazolidinone is 90% or less,
The higher the proportion of sulfolane, the lower the discharge capacity deterioration rate. In particular, Battery J using sulfolane alone as a solvent has a low discharge capacity deterioration rate of 5%, and is excellent in continuous overcharge characteristics. Therefore, it can be said that a battery using a solvent mainly containing sulfolane has a smaller discharge capacity deterioration rate during continuous charging than a battery mainly containing methyl oxazolidinone.

When judging from the viewpoint of the discharge characteristics and the continuous charge characteristics in a low-temperature environment as the battery performance required for the organic electrolyte battery, compared with the solvent using methyloxazolidinone alone, sulfolane, 3-methylsulfolane, Mixing with tetraglyme is preferred. In particular,
A solvent containing sulfolane, 3-methylsulfolane, and tetraglyme, in which the ratio of methyloxazolidinone in the solvent is set to 90% or less, is preferable from the viewpoint of battery performance.

In addition, batteries that place more emphasis on continuous charge characteristics than discharge characteristics under low-temperature environments, such as batteries mainly used for memory backup of various devices that are supposed to be used in normal temperature environments, are not suitable for use in solvents. Is preferably in the range of 5 to 60%. In this example, the solvent in which sulfolane was added to methyl oxazolidinone was described.However, by adding 3-methylsulfolane or tetraglyme to methyl oxazolidinone, the discharge characteristics and the continuous charge characteristics in a low-temperature environment were both achieved. A battery was obtained.

[0071]

As described above, according to the present invention, a solvent mainly composed of methyl oxazolidinone, or at least one selected from the group consisting of methyl oxazolidinone, sulfolane, 3-methylsulfolane and tetraglyme is used in the organic electrolyte. By using a mixed organic solvent in combination with one and the other, it is possible to provide an organic electrolyte solution that has high temperature resistance characteristics that can withstand substrate mounting using a reflow method, and also has excellent discharge characteristics in a low temperature environment and excellent continuous charge characteristics. Yes, its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of an organic electrolyte battery according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode can 2 Negative electrode can 3 Gasket 4 Positive electrode 5 Negative electrode 6 Separator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsuo Mori 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Terms (Reference) 5H011 AA02 AA03 AA09 CC06 DD15 GG02 5H024 AA03 AA12 BB07 CC03 DD04 DD09 EE09 FF14 FF19 FF20 HH00 5H029 AJ01 AJ04 AJ14 AK03 AL12 AM02 AM05 AM07 BJ03 CJ01 CJ08 DJ02 DJ03 DJ04

Claims (13)

[Claims] 1. An organic electrolyte battery in which a power generating element comprising a positive electrode, a negative electrode, a separator and an organic electrolyte is housed in a housing member having a positive electrode can, a negative electrode can, and a gasket, wherein the organic electrolyte is An organic electrolyte battery comprising: an organic solvent mainly composed of methyl oxazolidinone; and a solute mainly composed of a lithium salt having a sulfone group. 2. The organic electrolyte battery according to claim 1, wherein the lithium salt having a sulfone group is lithium trifluoromethanesulfonate. 3. The organic electrolyte battery according to claim 1, wherein the lithium salt having a sulfone group is a lithium salt having an imide bond in its molecular structure. 4. The organic electrolyte battery according to claim 3, wherein the lithium salt having a sulfone group and an imide bond is lithium bisperfluoromethylsulfonylimide. 5. The organic electrolyte battery according to claim 3, wherein the lithium salt having a sulfone group and an imide bond is lithium bisperfluoroethylsulfonylimide. 6. An organic electrolyte battery in which a power generating element comprising a positive electrode, a negative electrode, a separator and an organic electrolyte is housed in a housing member having a positive electrode can, a negative electrode can, and a gasket, wherein the organic electrolyte is , Sulfolane, 3-methylsulfolane, a mixed organic solvent obtained by mixing at least one kind of solvent selected from the group of tetraglyme and methyloxazolidinone, and a solute mainly composed of a lithium salt having a sulfone group. Characteristic organic electrolyte battery. 7. The organic electrolyte battery according to claim 6, wherein the mixed organic solvent contains methyl oxazolidinone at a volume fraction of 1 to 90%. 8. The organic electrolyte battery according to claim 6, wherein the lithium salt having a sulfone group is lithium trifluoromethanesulfonate. 9. The organic electrolyte battery according to claim 6, wherein the lithium salt having a sulfone group is a lithium salt having an imide bond in its molecular structure. 10. The organic electrolyte battery according to claim 9, wherein the lithium salt having a sulfone group and an imide bond is lithium bisperfluoromethylsulfonylimide. 11. The organic electrolyte battery according to claim 9, wherein the lithium salt having a sulfone group and an imide bond is lithium bisperfluoroethylsulfonylimide. 12. An organic electrolyte battery in which a power generating element including a positive electrode, a negative electrode, a separator, and an organic electrolyte is housed in a housing member having a positive electrode can, a negative electrode can, and a gasket, wherein the organic electrolyte is And an organic solvent containing methyl oxazolidinone, a solute mainly containing a lithium salt having a sulfone group, and the gasket is made of polyphenylene sulfide. 13. An organic electrolyte battery in which a power generating element comprising a positive electrode, a negative electrode, a separator and an organic electrolyte is housed in a housing member having a positive electrode can, a negative electrode can and a gasket, wherein the organic electrolyte is An organic electrolyte battery comprising: an organic solvent containing methyl oxazolidinone; a solute mainly containing a lithium salt having a sulfone group; and the separator is made of polyphenylene sulfide or cellulose.