JP4759784B2 - Organic electrolyte battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electrolyte battery used for a main power source of an electronic device or a memory backup power source, and enhances reliability at high temperature storage by imparting high temperature heat resistance to a power generation element and a housing member, and a reflow method. The present invention relates to an organic electrolyte battery that can be mounted on a substrate by automatic soldering.
[0002]
[Prior art]
In general, an organic electrolyte battery using lithium or an alloy thereof as a negative electrode has high energy density, can be reduced in size and weight, and has excellent reliability such as storage characteristics and leakage resistance. Therefore, the demand for the main power source of various electronic devices and the power source for memory backup is increasing year by year. In this type of battery, primary batteries that cannot be recharged are the mainstream. However, as rechargeable secondary batteries, a battery in which a lithium aluminum alloy or the like is combined with the negative electrode and vanadium pentoxide or lithium manganate is combined with the positive electrode is known. A coin-type organic electrolyte battery in which these power generation elements are housed in a flat battery container has been put into practical use.
[0003]
In recent years, a coin-type organic electrolyte battery has been suitably used as a memory backup power source for small portable devices, and recently, a battery having a battery diameter of 6 mm or less has been actively developed. The mounting of such a battery on a circuit board results in a significant increase in man-hours when a manual mounting method is employed because the battery and the circuit board are miniaturized. Therefore, as an efficient mounting method, attempts have been made to mount battery lead terminals by automatic soldering using a reflow method.
[0004]
[Problems to be solved by the invention]
Mounting on a circuit board by the reflow method is performed by passing a battery through a reflow furnace. Although the inside of the reflow furnace is in a short time, it is in a high temperature state, and particularly at a peak time, it is in an extremely high temperature state of 250 ° C. for about several tens of seconds. For this reason, it is desirable that at least the boiling point of the solvent of the electrolytic solution is 250 ° C. or higher.
[0005]
However, the boiling points of propylene carbonate and ethylene carbonate, which are organic solvents mainly used in organic electrolyte batteries, are 250 ° C. or less. When such an organic electrolyte battery is passed through a reflow furnace, the electrolyte inside the battery is instantaneously vaporized. For this reason, the internal pressure of the battery suddenly rises and may burst.
[0006]
In addition, the solvent reduces the viscosity of the solvent to increase the mobility of lithium ions and smoothly advance the discharge reaction of the battery, such as diethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, etc. In general, a constant viscosity solvent is added. However, since these solvents have a low boiling point of around 100 ° C., the boiling point of the electrolytic solution is lowered inside the reflow furnace, and the increase in pressure accompanying a rapid temperature increase is promoted.
[0007]
On the other hand, lithium perchlorate, lithium phosphorous hexafluoride, and the like are used as the lithium salt used as the solvent of the organic electrolyte, and the thermal decomposition temperatures thereof are all around 100 ° C. If the reflow furnace is exposed to a high temperature of 250 ° C. for a moment, the lithium salt is thermally decomposed, its function is lost, and a normal battery reaction is not performed.
[0008]
Furthermore, the heat resistance with respect to each component constituting the organic electrolyte battery is also important. In general, the positive electrode can, the gasket for insulating the negative electrode can, and the separator for insulating the positive electrode and the negative electrode are both made of polypropylene. The heat softening temperature of polypropylene is 100 to 120 ° C., and the gasket and the separator are exposed to a temperature significantly higher than the heat softening temperature when passing through the reflow furnace, and are damaged by heat.
[0009]
An organic electrolyte battery in which heat resistance is imparted to the constituent elements of the battery is known for the problem of the battery that occurs in a high temperature environment. (Described in JP-A-8-32287). This organic electrolyte battery includes an organic electrolyte obtained by dissolving a lithium salt 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, continuous use temperature As a specific example, a thermoplastic synthetic resin having a temperature of at least 150 ° C. is used, and as a specific example, an organic electrolyte containing lithium borofluoride as a solute is used as a solvent mainly composed of γ-butyllactone, and a separator and a gasket It is disclosed in the above-mentioned publication that a resin such as polyphenylene sulfide is used.
[0010]
However, this organic electrolyte battery is intended to provide an organic electrolyte battery that can be used and / or stored for a long period of time in a high-temperature environment exceeding 150 ° C. It does not have heat resistance under the above environment, and the same problems as conventional examples such as rapid vaporization of organic electrolyte, decomposition of solute, and damage of gasket and separator occur.
[0011]
As described above, the organic electrolyte battery does not have the high temperature resistance in the reflow furnace reaching 250 ° C., corresponds to the automatic soldering, and the organic electrolyte battery that can be mounted on the circuit board by using the reflow method is still not yet available. Not practical.
[0012]
In consideration of various conditions at the time of mounting on the circuit board, the present invention provides battery characteristics even when exposed to a high temperature of about 250 ° C. by imparting high temperature resistance to the power generation element and the battery housing. Accordingly, an object of the present invention is to provide an organic electrolyte battery that can be mounted using a reflow method without causing deterioration of the above.
[0013]
[Means for Solving the Problems]
To achieve the above objective, Departure Ming is an organic electrolyte battery in which a power generation element composed of 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, An organic solvent composed of a mixed solvent obtained by mixing at least one of sulfolane and 3-methylsulfolane with tetraglyme contained in a volume fraction of 5 to 100% or tetraglyme alone; From solutes mainly composed of lithium borofluoride And the gasket is made of polyphenylene sulfide and the separator is made of polyphenylene sulfide or cellulose. It is characterized by that.
[0014]
The boiling point of tetraglyme is 275 ° C., which is higher than the temperature inside the reflow furnace. Therefore, in the temperature range near 250 ° C., tetraglyme has a relatively high vapor pressure, but is in a relatively stable state. Furthermore, since the lithium salt is dissolved as a solute, the boiling point of the organic electrolyte battery of the present invention mainly composed of tetraglyme is higher than the boiling point of tetraglyme alone due to an increase in the molar boiling point, resulting in a high temperature environment. It works effectively with the following characteristics.
[0015]
In contrast to good characteristics in a high temperature range, an organic electrolyte using a solvent mainly composed of tetraglyme has good characteristics even in a low temperature range. As a requirement for the organic electrolyte battery, securing of discharge characteristics in a low temperature environment can be mentioned. In general, a solvent having a high boiling point tends to have a high melting point and a high viscosity. For this reason, the electrical conductivity of the electrolytic solution in the low temperature region is low. For example, when the temperature is lowered to −20 ° C., lithium ions in the organic electrolytic solution cannot move effectively, and the discharge capacity is hardly obtained. Become. In contrast, tetraglyme is characterized by a low melting point of −30 ° C. and a wide temperature range of about 300 ° C., although it has a high boiling point of 275 ° C. By using tetraglyme as a solvent, the organic electrolyte can maintain electrical conductivity even in an environment of −20 ° C. Furthermore, the lithium salt moves smoothly during the discharge reaction, and a discharge capacity of 30% or more of the predetermined capacity can be obtained in a wide temperature range, for example, in the range of −20 ° C. to 250 ° C.
[0016]
On the other hand, lithium borofluoride was used as a solute dissolved in the organic solvent containing the tetraglyme of the present invention. The characteristics of lithium salts applied to organic electrolytes for the purpose of imparting high-temperature resistance include the thermal decomposition temperature of lithium salts, the conductivity of the electrolyte, and the low corrosiveness to the materials of the positive and negative electrode cans. There is a need to.
[0017]
Since the thermal decomposition temperature of lithium borofluoride greatly exceeds 200 ° C., it is stable even when left at a temperature of 250 ° C. In contrast, lithium perchlorate, lithium hexafluoride, and the like 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 lithium borofluoride as a solute enables a smooth battery reaction to proceed even in a high temperature environment.
[0018]
Moreover, the lithium salt which has a sulfone group also has a very high thermal decomposition temperature. Examples of the lithium salt having a sulfone group include lithium trifluoromethanesulfonate, lithium bisperfluoromethylsulfonylimide having an imide bond in the molecular structure, or lithium bisperfluoroethylsulfonylimide. Even when these solutes are used, the high-temperature characteristics and the low-temperature characteristics are equivalent to or higher than those obtained when lithium borofluoride is used.
[0019]
In view of the above characteristics, the present inventors previously proposed a high-temperature battery using a lithium salt having a sulfone group as a solute, and using an organic electrolyte composed of a solvent mainly composed of tetraglyme as a solvent. (Japanese Patent Application No. 10-345095). However, the lithium salt having a sulfone group has a problem that it is very corrosive. In addition, lithium salts having a sulfone group such as lithium trifluoromethanesulfonate and lithium bisperfluoromethylsulfonylimide easily dissolve the aluminum used in the positive electrode current collector of the lithium ion secondary battery. It is not adopted as a solute for secondary batteries. On the other hand, lithium borofluoride and phosphorus hexafluoride have low corrosivity and do not dissolve aluminum, and are used as solutes for lithium ion secondary batteries.
[0020]
When using an organic electrolyte containing a lithium salt having a sulfone group as a solute and tetraglyme as a main solvent and stored at 150 ° C. for a long time after passing through a reflow furnace, the stainless steel constituting the positive electrode can be corroded, and the electrolyte Stainless steel elutes inside. The stainless steel eluted in the electrolyte solution is deposited on the negative electrode surface, increasing the internal resistance of the battery and degrading the discharge characteristics of the battery. Also, if this corrosion reaction is severe, stainless steel will short-circuit the positive and negative electrodes inside the battery and the discharge will proceed, the battery voltage of 3V or more will drop to near 0V, the positive electrode can will have a hole, and the electrolyte will It goes out through the hole and leaks.
[0021]
On the other hand, by using an organic electrolytic solution containing lithium borofluoride as a solute and tetraglyme as a main solvent and being stored at 150 ° C. for a long time after passing through a reflow furnace, the corrosiveness of lithium borofluoride is low. No problems due to corrosion occur, and very high temperature storage characteristics can be obtained.
[0022]
In addition, as a solvent, although the structure which has a tetraglyme as a main component and another solvent may be mixed in this, the structure using the single solvent which consists only of tetraglyme is preferable. A battery using an organic electrolyte composed of a solvent of tetraglyme alone has the best discharge characteristics.
[0023]
As described above, by using an organic solvent mainly composed of tetraglyme and an organic solvent having lithium borofluoride as a solute, it is possible to obtain an organic electrolyte secondary battery in which the high temperature resistance is dramatically improved. .
[0025]
Organic electrolytes using sulfolane and 3-methylsulfolane are superior in that they are less reactive to the positive electrode and negative electrode than organic electrolytes using only tetraglyme and are less likely to cause gas generation reactions due to decomposition of the electrolyte. ing.
[0026]
For the purpose of imparting high temperature resistance characteristics to an electrolytic solution, the inventors of the present invention comprise an organic solvent composed of a mixed organic solvent composed of 3-methylsulfolane and sulfolane and a solute mainly composed of a lithium salt having a sulfone group. A battery using an electrolytic solution was proposed (Japanese Patent Application No. 10-217266). This proposal also reveals that the boiling point of sulfolane is about 287 ° C. and the boiling point of 3-methylsulfolane is about 275 ° C., which is higher than the temperature inside the reflow furnace and even in a high temperature atmosphere when passing through the reflow furnace. It has stable characteristics. On the other hand, the freezing points of sulfolane and 3methylsulfolane are 28 ° C. and 6 ° C., respectively. When these solvents are used as organic electrolytes, the freezing point can be lowered by the lithium salt as a solute, and the solidification temperature can be moved to the low temperature side. It is difficult to do. Furthermore, since the electrical conductivity in a low temperature range is low, an organic electrolyte battery using only these solvents causes a significant deterioration in discharge characteristics.
[0027]
However, by adding tetraglyme to this mixed solvent, an improvement in the low-temperature characteristics is recognized due to a decrease in the viscosity of the electrolytic solution and an improvement in the liquid absorbency at the positive electrode resulting therefrom. In particular, by adding 5% or more of tetraglyme, 30% or more of the discharge capacity at 25 ° C. can be maintained even at −20 ° C. discharge, and the discharge characteristics in the low temperature range can be improved.
[0028]
Here, the volume fraction of tetraglyme in the organic solvent to which sulfolane or 3-methylsulfolane is added is preferably in the range of 5 to 90%. In particular, when the volume fraction of tetraglyme exceeds 90%, the self-discharge rate is increased. It increases rapidly and affects the effect obtained by the addition of sulfolane and 3-methylsulfolane, that is, long-term reliability. As for the high temperature resistance, there is no difference between an organic solvent composed only of tetraglyme or a mixed solvent type electrolyte obtained by mixing at least one kind of sulfolane and 3 methylsulfolane with tetraglyme.
[0030]
The gasket also has a function as an insulating packing that insulates the positive electrode can and the negative electrode can, and is formed by injection molding into a shape along the inner peripheral surface between the positive electrodes. Moreover, the separator is formed of a nonwoven fabric made of polyphenylene sulfide, and instead of this, a paper separator made of cellulose may be used.
[0031]
The polyphenylene sulfide used in the separator and gasket of the present invention has been found from the stability to the electrolytic solution in addition to the heat resistance. Polyphenylene sulfide has a heat softening temperature of 200 ° C. or higher, and is not thermally deformed even at a high temperature of about 250 ° C. by the addition of a filler such as glass fiber. For this reason, each function as a gasket and a separator can be maintained even in a high temperature environment inside the reflow furnace. The same can be said for cellulose.
[0032]
In addition, polyphenylene sulfide and cellulose have a characteristic that they are chemically stable without being dissolved in the solvent of sulfolane, 3methylsulfolane, or tetraglyme used in the organic electrolyte solution according to the present invention. This characteristic makes it possible to obtain long-term reliability.
[0033]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0034]
(First embodiment)
FIG. 1 is a cross-sectional view of an organic electrolyte secondary battery in the present embodiment. The battery dimensions are 6.8 mm in diameter and 2.1 mm in thickness. In FIG. 1, the positive electrode can 1 also serves as a positive electrode terminal and is made of stainless steel having excellent corrosion resistance. The negative electrode can 2 also serves as a negative electrode terminal and is made of stainless steel made of the same material as the positive electrode can 1. The gasket 3 insulates the positive electrode can 1 and the negative electrode can 2 and is made of polyphenylene sulfide. Further, a pitch is applied to the surface of the gasket 3 on the surface in contact with the positive electrode can and the negative electrode can. The positive electrode 4 is obtained by mixing vanadium pentoxide, which is an active material, with carbon black as a conductive agent and fluororesin powder as a binder, and forming into a pellet shape having a diameter of 4 mm and a thickness of 1.2 mm. Time dried. The negative electrode 5 is formed by punching an aluminum-manganese alloy containing 5 wt% manganese metal into a disk shape having a diameter of 4 mm and a thickness of 0.3 mm and press-contacting the inside of the negative electrode can 2. In addition, to form an alloy with lithium, a lithium foil is pressure-bonded to the surface of the aluminum alloy at the time of battery assembly, and lithium is occluded in the aluminum alloy in the presence of an electrolytic solution to make a lithium-aluminum alloy electrochemically. This is used as the negative electrode. A separator 6 made of polyphenylene sulfide non-woven fabric was disposed between the positive electrode 4 and the negative electrode 5.
[0035]
In the organic electrolyte, tetraglyme was used as a solvent, and lithium borofluoride dissolved as a lithium salt at a ratio of 1 mol / l was used. 15 μl of this is filled in a battery container composed of a positive electrode can 1, a negative electrode can 2 and a gasket 3. The created battery is referred to as battery A.
[0036]
In place of the organic electrolyte in battery A, lithium trifluoromethanoate was used as the solute lithium salt, and the organic electrolyte was dissolved in tetraglyme as a solvent at a ratio of 1 mol / l. A battery B, the same as A, was created.
[0037]
Moreover, it replaced with the organic electrolyte solution in the battery A, and used the mixed solvent which mixed the tetraglyme and the sulfolane so that the volume fraction might be 65% and 35%, respectively, and lithium borofluoride was made into the ratio of 1 mol / l. A battery C having the same configuration as that of the battery A was prepared using the dissolved organic electrolyte.
[0038]
Similarly, in place of the organic electrolyte solution in battery A, a mixed solvent in which tetraglyme, sulfolane, and 3 methylsulfolane were mixed so that the volume fractions were 65%, 25%, and 10%, respectively, was used, and lithium borofluoride was used. A battery D having the same structure as that of the battery A was prepared using an organic electrolytic solution in which is dissolved at a ratio of 1 mol / l.
[0039]
Next, instead of the separator made of non-woven fabric made of polyphenylene sulfide in the battery A, a paper separator made of cellulose was used, and a battery E having the same configuration as that of the battery A was prepared.
[0040]
On the other hand, as a comparative example, instead of the organic electrolyte solution in battery A, a solute composed of lithium borofluoride is dissolved at 1 mol / l in a solvent composed of propylene carbonate, and the other configuration is a comparative product F equivalent to battery A. .
[0041]
Furthermore, instead of the organic electrolyte in battery A, tetraglyme is used as a solvent, and an organic electrolyte obtained by dissolving lithium hexafluoride as a lithium salt at a ratio of 1 mol / l is used. Comparative product G, which is the same as battery A, was prepared. Moreover, it replaced with the separator in the battery A, the separator made from a polypropylene was used, and the comparative product H which made the other structure the same as the battery A was created. Further, a gasket made of polypropylene is used instead of the gasket in the battery A, and the other configuration is the comparative product I which is the same as the battery A. The structures of the batteries A to E and the comparative products F to I thus obtained are shown in (Table 1).
[0042]
[Table 1]
[0043]
(Second Embodiment)
As a second embodiment, by using a solvent in which the mixing ratio of tetraglyme and sulfolane is variously changed, an organic electrolyte solution in which lithium borofluoride is dissolved as a solute in these solvents at a ratio of 1 mol / l is prepared. Using these organic electrolytes. A battery having the configuration shown in FIG. 1 as in Example 1. L, M, N, P, Q and comparative products J, K It was created. The positive electrode was vanadium pentoxide, the negative electrode was a lithium-aluminum alloy, and the gasket and separator were polyphenylene sulfide. The mixing ratio of tetraglyme and sulfolane in the organic electrolyte solution of these batteries is shown in (Table 2).
[0044]
[Table 2]
[0045]
(Third embodiment)
As a third embodiment, the volume fractions of tetraglyme and sulfolane are 30% and 70%, respectively, and dissolved in these solvents as a solute at a ratio of 1 mol / l each of lithium borofluoride to prepare an organic electrolyte. . Using this organic electrolytic solution, 50 batteries R having the configuration shown in FIG. The positive electrode was vanadium pentoxide, the negative electrode was a lithium-aluminum alloy, and the gasket and separator were polyphenylene sulfide.
[0046]
Further, lithium trifluoromethanesulfonate was used instead of the electrolyte solute in the battery R, and this was used in a solvent mixture of tetraglyme and sulfolane at a ratio of 1 mol / l to a mixed solvent of 30% and 70%. Using an organic electrolytic solution in which lithium borofluoride was dissolved, 50 batteries S having the same configuration as the battery R were prepared.
[0047]
【Example】
Examples of the present invention will be described below.
[0048]
Example 1
In Example 1, evaluation was performed on the batteries A to E and the comparative products F to I created in the above embodiment.
[0049]
First, for each of the batteries shown in Table 1, the initial internal resistance (AC method 1 kHz) was confirmed, and then a load of 100 kΩ was connected to measure the discharge capacity. The discharge capacity was determined by the ratio of the theoretical capacity of the organic electrolyte battery in this example to 100. Furthermore, a charge / discharge cycle test was also performed for each of the obtained batteries A to E and comparative products F to I. The test conditions were such that the battery voltage was repeatedly charged and discharged at a constant current of 0.1 mA between 3.35 V and 2.5 V, and the number of times that charging / discharging was possible was determined.
[0050]
At the same time, a reflow passage test for passing through the inside of the high-frequency heating type reflow furnace was performed, and the high temperature resistance characteristics for the batteries A to E and the comparative products F to I were examined. As for the temperature profile of the reflow furnace, 180 ° C. was passed for 2 minutes as the preheating step, and then 180 ° C. → 245 ° C. → 180 ° C. was passed for 30 seconds as the heating step, and then naturally cooled to room temperature. After the battery is sufficiently cooled, a visual inspection and a voltage inspection are performed according to the appearance, and for a battery that does not cause a problem, after the internal resistance is measured again, the battery is passed through a reflow furnace with the same temperature profile as described above. Inspection and measurement were performed. After repeating this three times, the degree of deterioration was confirmed in comparison with the initial state. The results are shown in (Table 3).
[0051]
[Table 3]
[0052]
(Table 3) shows that the discharge capacity of battery A is 90% of the theoretical value, the reflow passage test shows no abnormality up to three times, and the internal resistance value after passage hardly changes from the initial state. Therefore, no thermal damage due to reflow was observed, and good results were obtained. Next, the battery B using lithium trifluoromethaneate as the lithium salt has an initial internal resistance value higher than that of the battery A. However, like the battery A, no abnormality was observed up to three reflow passage tests, and good results were obtained in terms of electrical characteristics. Further, since the battery C uses a mixed solvent in which sulfolane is mixed at a ratio of 35%, the viscosity of the electrolytic solution is increased and the initial internal resistance is high. However, in the discharge capacity and charge / discharge cycle, better results were obtained than in the battery A, and no abnormality was observed even after three reflow passage tests. In addition, the battery D to which sulfolane and 3-methylsulfolane were added further improved the electric characteristics in the battery electric characteristics.
[0053]
On the other hand, since the battery E used a paper separator made of cellulose, the initial internal resistance value was higher than that of the battery A, but good results were obtained for other results as well.
[0054]
In contrast to these results, in comparative product F, propylene carbonate used as a solvent boiled while passing through the reflow furnace, and bursting occurred due to an increase in internal pressure due to this. In Comparative Product G, lithium phosphorus hexafluoride used as the lithium salt was thermally decomposed while passing through the reflow furnace, and the resistance of the electrolyte increased. This results in an increase in internal resistance, indicating that the electrical characteristics of the battery have been destroyed.
[0055]
Further, in 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 melted and contracted, and the positive electrode and the negative electrode contacted each other. Further, in Comparative Product I, liquid leakage was observed from a gasket using polypropylene. This is because the gasket melted and contracted due to the same phenomenon as that of the comparative product H, and liquid leakage occurred from this portion.
[0056]
Regarding the number of charge / discharge cycles, the electrolyte solution using lithium borofluoride as the lithium salt was able to be charged and discharged about 80 times or more regardless of the type of solvent.
[0057]
From the above, the batteries A to E in this example were able to find excellent results in any of the discharge performance, charge / discharge cycle performance, and high-temperature resistance during reflow. This is due to the heat resistance of tetraglyme, which is the solvent main component of the electrolytic solution, the heat resistance of lithium borofluoride, which is the lithium salt, excellent conductivity, and stability against the lithium aluminum alloy negative electrode, and further, battery components This is because the use of polyphenylene sulfide PPS for the gasket and the non-woven fabric made of polyphenylene sulfide PPS for the separator makes it possible to obtain heat resistance during reflow.
[0058]
(Example 2)
As Example 2, the battery created in the second embodiment L, M, N, P, Q and comparative products J, K We conducted a reflow passage test that passed through the inside of a high-frequency heating reflow furnace and examined the high temperature resistance. The test method was carried out by passing the reflow furnace twice with the same temperature profile as in Example 1. After the test, the occurrence of rupture and leakage was confirmed visually. L, M, N, P, Q and comparative products J, K No leakage or rupture was observed for any of the batteries.
[0059]
Furthermore, using the battery after performing the reflow furnace passing test, it was connected to a resistance of 300 kΩ at −20 ° C., and a discharge test was performed. Similarly, using the battery used in the reflow furnace passage test, the battery was left in a constant temperature bath at 60 ° C. for 40 days, and then connected to a resistance of 51 kΩ at room temperature to conduct a discharge test. Based on the measurement of the discharge capacity obtained by these discharge tests, the ratio to the theoretical capacity was obtained in the same manner as in Example 1, and this is shown in Table 4. Furthermore, the self-discharge rate is determined from the discharge capacity at the initial storage of the reflow furnace passage test and the discharge capacity after storage, and is shown in (Table 4).
[0060]
[Table 4]
[0061]
From (Table 4), Comparison product J uses only sulfolane as a solvent, and hardly discharges in an environment of −20 ° C. This is considered to be due to the solidification of the electrolytic solution itself. On the other hand, containing tetraglyme Comparative product K and batteries L, M, N, P, Q With regard to, the discharge capacity in a low temperature environment increased with an increase in the proportion of tetraglyme in the solvent. In particular, the battery Q using tetraglyme alone as a solvent can obtain the best results in terms of discharge capacity under this environment. From these facts, when a solvent composed only of sulfolane is used, the electrolytic solution is solidified at −20 ° C. However, by adding tetraglyme to the solvent, the electrolytic solution is not solidified, and in a low temperature environment. Allows to discharge. At this time, the effect of improving the electroconductivity of electrolyte solution itself is also considered.
[0062]
On the other hand, in terms of self-discharge rate, only sulfolane was used. Comparison product J is preferred. In Battery Q using a solvent consisting only of tetraglyme, the self-discharge rate was as high as 30% or more. This increase in the self-discharge rate shows a difference when the volume fraction of tetraglyme in the solvent reaches 90%, and the self-discharge rate deteriorates rapidly in the batteries P and Q having a high tetraglyme ratio. On the other hand, the volume fraction of tetraglyme is 90% or less Comparative products J, K and batteries L, M, N Then, the higher the proportion of sulfolane, the lower the self-discharge rate. In particular, sulfolane alone was used as a solvent. Comparison product J has a low self-discharge rate of 4% and is excellent in long-term storage reliability. Therefore, it can be said that a battery using a solvent mainly containing sulfolane has a lower self-discharge rate than a battery mainly containing tetraglyme.
[0063]
As battery performance required for an organic electrolyte battery, it is preferable to mix with sulfolane and 3 methylsulfolane, compared to a solvent using tetraglyme as a simple substance, judging from discharge characteristics in a low temperature environment and long-term reliability. . In particular, a solvent containing sulfolane and 3 methylsulfolane and having a tetraglyme ratio in the solvent set to 90% or less is preferable from the viewpoint of battery performance.
[0064]
In addition, batteries that place an emphasis on long-term reliability compared to discharge characteristics in a low-temperature environment, such as batteries mainly used for memory backup of various devices that are presumed to be used in a room-temperature environment, occupy tetra. The glyme ratio is preferably in the range of 5 to 60%. In addition, although the present Example demonstrated the solvent which added the sulfolane to the tetraglyme, the battery which was compatible with the discharge characteristic in a low temperature environment and a low self-discharge rate is obtained also by adding 3 methyl sulfolane to a tetraglyme. It was.
[0065]
(Example 3)
As Example 3, a reflow passage test in which the inside of the high-frequency heating type reflow furnace was passed through the battery R and the battery S was performed, and the high temperature resistance characteristics were examined. In this test method, the reflow furnace was passed twice with the same temperature profile as in Example 1. After the test, the occurrence of rupture and leakage was confirmed visually, but no leakage or rupture was observed for any of the batteries R and S.
[0066]
Further, the battery after the reflow furnace passage test was stored in a thermostatic bath at 150 ° C. for 30 days, and the change in internal resistance was followed. The internal resistance was measured at an alternating current of 1 KHZ after being taken out from a bath at 150 ° C. and allowed to stand at room temperature for several hours. The change in internal resistance when stored at 150 ° C. is shown in (Table 5). The internal resistance values shown in (Table 5) are average values of 50 batteries R and S. In addition, the occurrence rate of the battery whose battery voltage is reduced to 1 V or less is shown in (Table 5).
[0067]
[Table 5]
[0068]
From the results of (Table 5), the battery S using lithium trifluoromethanesulfonate as the solute had a battery internal resistance of 1000Ω or more when left at 150 ° C. for 10 days, whereas lithium borofluoride was used as the solute. The battery R used exhibited an internal resistance value that was not significantly different from the initial value. In addition, the number of batteries whose battery voltage dropped to 1 V or less increased as the number of storage days increased, and the number of batteries S reached the total on the 30th day. On the other hand, in the battery R, the battery voltage never became 1 V or less. When the battery K whose battery voltage dropped to 1 V or lower was disassembled, blackened portions were scattered on the surface of the lithium aluminum alloy of the negative electrode. Moreover, the blackened part was seen also in the separator. As a result of analyzing the black portion by fluorescent X-ray, it was found that the black portion is stainless steel which is a material of the positive electrode can. The stainless steel on the inner surface of the positive electrode can in contact with the positive electrode was corroded, and the dissolved one was deposited on the lithium aluminum alloy of the negative electrode, increasing the internal resistance of the battery. As the corrosion reaction of the stainless steel further progresses, the stainless steel causes the positive electrode and the negative electrode to be short-circuited inside the battery, so that the battery voltage, which was initially 3 V or higher, decreased to 1 V or lower. When the battery R after storage was disassembled, the stainless steel of the positive electrode can was not corroded. The cause of the increase in internal resistance is thought to be due to the organic coating produced by the reaction between the electrolyte and the lithium aluminum alloy of the negative electrode.
[0069]
By using lithium borofluoride as a solute, very excellent characteristics were obtained even when stored at 150 ° C. at a high temperature.
[0070]
【The invention's effect】
As described above, according to the present invention, a solvent mainly composed of tetraglyme in an organic electrolyte solution, or a mixed solvent of tetraglyme and at least one of sulfolane and 3methylsulfolane and lithium borofluoride as a solute. By using this, it is possible to provide an organic electrolyte that has high temperature resistance that can withstand substrate mounting using the reflow method, and that is excellent in discharge characteristics under a low temperature environment and high temperature continuous storage characteristics at 150 ° C., Its industrial value is great.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the configuration of an organic electrolyte battery in this example
[Explanation of symbols]
1 Positive electrode can
2 Negative electrode can
3 Gasket
4 Positive electrode
5 Negative electrode
6 Separator

Claims (1)

An organic electrolyte battery in which a power generation element composed of 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 5 to 100% in tetraglyme contained in the volume fraction, Ri Do sulfolane, 3-methylsulfonyl an organic solvent comprising a mixed solvent or tetraglyme alone was mixed at least one of the run, a solute composed mainly of lithium borofluoride, and wherein said gasket is polyphenylene sulfide, organic electrolyte battery in which the separator and wherein Rukoto a polyphenylene sulfide, or cellulose.