Organic electrolyte battery

The present invention relates to an organic electrolyte battery configured by sealing power generating elements comprising an organic electrolyte by a positive can, a negative can and a gasket, wherein said organic electrolyte includes a lithium salt containing a sulfonic acid group as a solute and at least one selected from a group consisting of sulfolane, 3-methyl sulfolane and Tetraglyme as a solvent. The aim of the invention is to provide an organic electrolyte battery having an excellent discharge performance in a low temperature environment and a superior reliability during long term storage, as well as a high temperature resistance which enables the battery to be mounted onto a substrate according to the Reflow method.

BACKGROUND OF THE INVENTION
 The present invention relates to a battery including an organic electrolyte
 (organic electrolyte battery) used for primary or memory back-up power
 sources of electronic appliances. More particularly, the present invention
 relates to a coin-shaped organic electrolyte battery with thermal
 resistance at a high temperature which can be mounted onto a circuit
 substrate by automatic soldering according to the Reflow method.
 Organic electrolyte batteries generally have a high energy density so that
 it is possible to make the electronic appliances compact and light. Also,
 they have superior reliability in terms of storage characteristics and
 leakage resistance so that there is an increasing demand for them as
 primary and memory back-up power sources for various electronic
 appliances. Majority of this type of batteries are unchargeable primary
 batteries. Their representative experiment is batteries using metallic
 lithium as a negative electrode, and manganese dioxide, carbon fluoride,
 thionyl chloride, sulfur dioxide or silver chromate as a positive
 electrode.
 Recently, rechargeable secondary batteries have been developed, and
 particularly, coin-shaped lithium secondary batteries using a
 lithium-aluminum alloy or the like have been in practical use for several
 years. Among these batteries, those using vanadium pentoxide or lithium
 manganate as a positive electrode are generally used.
 A common organic electrolyte of such secondary batteries is one obtained by
 dissolving a lithium salt as a solute in a mixture solvent which contains
 a solvent having a high boiling point and a high dielectric constant and a
 solvent having a low boiling point and a low viscosity. For example, one
 or more solvents such as ethylene carbonate, propylene carbonate, butylene
 carbonate and .gamma.-butylolactone are used as the solvent having a high
 boiling point and a high dielectric constant. The low-viscosity solvents
 mixed for reducing viscosity and thereby enhancing conductivity are
 intended to facilitate movement of lithium ions and ensure smooth
 discharge reaction of the batteries. For example, one or more solvents
 such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran and
 1,3-dioxorane are used for this purpose. As the solute, lithium salts such
 as LiClO.sub.4, LiBF.sub.4, LiPF.sub.6 are generally known.
 However, the batteries including the above-described organic electrolyte
 have various problems, if left under a high temperature. For example, the
 organic electrolyte evaporates at a high temperature in the battery to be
 obtained. Especially, the low boiling point solvents in the mixture
 solvent, which is retained in a separator, evaporate due to the boiling
 point of as low as around 100.degree. C. Also, the above-mentioned lithium
 salts thermally decompose at a high temperature, thereby losing their
 function, since any of these lithium salts has a thermal decomposition
 temperature of around 100.degree. C. This means occurrence of a trouble
 which promotes deterioration of battery performance. Therefore, the
 organic electrolyte batteries have a limit of the temperature at which
 they can be used, with their upper limit set at 60 to 85.degree. C.
 Under these circumstances, vigorous development is recently in progress on
 an extremely compact, coin-shaped secondary batteries having a diameter of
 not more than 6 mm to serve as memory back-up power sources for
 small-sized portable appliances. In order to mount such extremely compact
 batteries onto print substrates, there has been a proposed method for
 mounting lead terminals of the batteries by an automatic soldering using
 the Reflow method. According to this proposal, however, the internal
 temperature of the Reflow furnace becomes high, although for a short time,
 and reaches as high as 250.degree. C. for dozens of seconds at the peak.
 Therefore, as described above, if the batteries of normal configuration
 are caused to pass the Reflow furnace, the oroganic electrolyte instantly
 vaporizes to raise internal pressure of the batteries, which may result in
 explosion of the batteries themselves.
 In addition, it is also important whether each component of the organic
 electrolyte batteries has sufficient thermal resistance. Generally, a
 gasket insulating a positive can and a negative can (a seal plate) and a
 separator insulating a positive electrode and a negative electrode are
 made of polypropylene. Since thermosoftening temperature of polypropylene
 is 100 to 120.degree. C., the gasket and the separator are damaged by
 heat, when they are exposed to a much higher temperature than the
 thermosoftening temperature in passing the Reflow furnace.
 In order to solve the problems of the batteries induced by such high
 temperature environment, there has been another proposal of the organic
 electrolyte batteries wherein battery components are conferred thermal
 resistance (for example, Japanese Laid-open Patent Publication Hei
 8-321287). The organic electrolyte batteries according to this proposal
 comprises an organic electrolyte obtained by dissolving a lithium salt as
 a solute in an organic solvent having a boiling point of not less than
 170.degree. C., a separator of porous synthetic resin sheet having a
 boiling point of not less than 170.degree. C. and a gasket of
 thermoplastic synthetic resin which can be continuously used at least at
 150.degree. C.
 More particularly, the proposed batteries use an organic electrolyte
 comprising lithium borofluoride dissolved as a solute in a solvent
 containing .gamma.-butylolactone, a separator and a gasket made of heat
 resistant resin such as polyphenylene sulfide.
 However, the proposed organic electrolyte batteries are intended to be used
 and stored in an environment of more than 150.degree. C. for a long
 period, thereby not having enough thermal resistance to withstand the
 temperature of not less than 250.degree. C. required for the Reflow
 method. Therefore, they also have the same problems as conventional other
 batteries such as the acute vaporization of the organic solvents, the
 decomposition of the solute and the damage of the gasket and the
 separator.
 As described above, the currently available organic electrolyte batteries
 do not have enough thermal resistance to endure 250.degree. C. of the
 Reflow furnace. As the result, the organic electrolyte batteries cannot
 yet be mounted onto a circuit substrate by the automatic soldering
 according to the Reflow method.
 Therefore, the object of the present invention is to provide an organ ic
 electrolyte battery having a high thermal resistance at a high temperature
 that has never accomplished before by combining solvents with lithium
 salts, both having thermal resistance and reliability.
 Further, the object of the present invention is to provide an organic
 electrolyte battery having an excellent thermal resistance that can endure
 the temperature of about 250.degree. C. required for the automatic
 soldering according to the Reflow method, by employing highly heat
 resistant materials compatible with an organic electrolyte for battery
 components such as a gasket and a separator.
 SUMMARY OF THE INVENTION
 The present invention relates to an organic electrolyte battery configured
 by sealing power generating elements comprising a positive electrode, a
 negative electrode, a separator which isolates both electrodes and an
 organic electrolyte by a positive can to serve as a positive terminal, a
 negative can to serve as a negative terminal and a gasket. And, the
 organic electrolyte battery of the present invention is characterized in
 that the above-mentioned organic electrolyte includes a lithium salt
 containing a sulfonic acid group as the solute and at least one selected
 from a group consisting of sulfolane, 3-methyl sulfolane and Tetraglyme
 (CH.sub.3 O(CH.sub.2 CH.sub.2 O).sub.4 CH.sub.3 ; tetraethyleneglycol
 dimethylether) as the solvent.
 It is preferable that said lithium salt containing a sulfonic acid group is
 lithium trifluoromethanesulfonate or a lithium salt containing an imide
 bond in the molecule.
 Also, it is preferable that said lithium salt containing an imide bond in
 the molecule is lithium bisperfluoromethyl sulfonyl imide or lithium
 bisperfluoroethyl sulfonyl imide.
 Also, it is preferable that said gasket is made of polyphenylene sulfide
 and that the above-mentioned separator is made of polyphenylene sulfide or
 cellulose.
 Also, it is preferable that a sealant made of at least one selected from a.
 group consisting of isobutylene-isoprene rubber, styrene-butadiene rubber
 and fluorocarbon resin of which a part of the side chains is substituted
 with a silicon resin is disposed at a portion where the above-mentioned
 gasket is in contact with the above-mentioned positive can and negative
 can.
 The above organic electrolyte battery can be applied to both primary and
 secondary battery.

DETAILED DESCRIPTION OF THE INVENTION
 In order to solve the above problems, the present invention provides an
 organic electrolyte battery which is configured by sealing power
 generating elements by a positive can, a negative can and a gasket,
 wherein the organic electrolyte includes a lithium salt containing a
 sulfonic acid group as the solute and at least one selected from a group
 consisting of sulfolane, 3-methyl sulfolane and Tetraglyme as the solvent.
 First, explanation will be given for the solute of the present invention.
 For the organic electrolyte used in the present invention, a lithium salt
 containing a sulfonic acid group is used as the solute. It is considered
 that the lithium salt which may be exposed to a high temperature is
 required to have the following two major properties.
 The first property is thermal decomposition temperature of the lithium
 salt. Lithium perchlorate (LiClO.sub.4), lithium hexafluorophosphate
 (LiPF.sub.6) and the like, generally used as a lithium salt for the
 organic electrolyte battery, have a thermal decomposition temperature of
 around 100.degree. C. Thus, if they are exposed to a high temperature of
 250.degree. C. even though for a moment, their function as a lithium salt
 is deteriorated or lost due to the thermal decomposition and abnormal
 battery reaction. Contrary to this, a lithium salt containing a sulfonic
 acid group in the structure is generally known to have a high thermal
 decomposition temperature. Especially, lithium bisperfluoromethyl sulfonyl
 imide (LiN(CF.sub.3 SO.sub.2).sub.2) or lithium bisperfluoroethyl sulfonyl
 imide (LiN(C.sub.2 F.sub.5 SO.sub.2).sub.2) has a thermal decomposition
 temperature remarkably higher than 200.degree. C. and they are still
 stable even when left under the temperature of as high as 250.degree. C.
 to develop a smooth battery reaction.
 The second property is influence on conductivity of the electrolyte. The
 higher conductivity of the electrolyte is preferable, and such
 conductivity is one of the most important factors which enables the
 battery to discharge a large amount of electric current. It is common to
 add a low viscosity solvent such as diethylene carbonate,
 1,2-dimethoxyethane or 1,2 diethoxyethane to the electrolyte, in order to
 reduce viscosity, enhance mobility of lithium ions and ensure smooth
 discharge reaction of the battery. However, these solvents lower the
 boiling point of the electrolyte itself due to their boiling point of as
 low as around 100.degree. C., thereby not appropriate for the use as
 described above. Therefore, it is required to use a lithium salt
 exhibiting a high conductivity when dissolved.
 On the other hand, particularly lithium bisperfluoromethyl sulfonyl imide
 or lithium bisperfluoroethyl sulfonyl imide has an imide bond in the
 molecular structure and mobility of their dissociation salts becomes high.
 Therefore, it is possible without the use of the low viscosity solvents to
 give conductivity to some extent and a smooth discharge reaction.
 Also, in case a lithium-aluminum alloy is used for the negative electrode,
 if a lithium salt has an imide bond, it has been discovered that the high
 conductivity of the lithium salt facilitates lithium dispersion on a
 surface of the aluminum alloy during lithium electrical deposition to
 drastically improve charge/discharge cycle performance.
 For the above-stated reasons, it is preferable for remarkably improving
 high thermal resistance at a high temperature of the organic electrolyte
 battery to be obtained, in the present invention, to use lithium
 trifluoromethanesulfonate (LiCF.sub.3 SO.sub.3), or lithium
 bisperfluoromethyl sulfonyl imide or lithium bisperfluoroethyl sulfonyl
 imide having an imide bond in the molecule as a lithium salt containing a
 sulfonic acid group.
 Next, explanation will be further given for the solvent of the organic
 electrolyte of the present invention.
 The solvent of the present invention contains at least one selected from
 the group consisting of sulfolane, 3-methyl sulfolane and Tetraglyme as
 the main component.
 (1) In Case Only Sulfolane is Used
 Since the Reflow furnace becomes as high as 250.degree. C., it is desirable
 that the boiling point of the solvent of the electrolyte is higher than
 250.degree. C. The boiling point of propylene carbonate or ethylene
 carbonate commonly used as the organic solvent is not more than
 250.degree. C. Thus, it is preferable to use a solvent containing
 sulfolane as the main component in the present invention. Sulfolane has a
 boiling point of about 280.degree. C. which is higher than the temperature
 of the Reflow furnace. And sulfolane is relatively in a stable condition
 at 250.degree. C., although it has the vapor pressure at 250.degree. C. In
 addition, by dissolving the above-mentioned lithium salt containing a
 sulfonic acid group as a solute, the organic electrolyte including
 sulfolane has a further raised boiling point due to elevation of boiling
 point, thereby working effectively.
 (2) In Case Only Tetraglyme is Used
 Tetraglyme has a boiling point of 275.degree. C., which is higher than the
 internal temperature of the Reflow furnace. Thus, in the temperature range
 of around 250.degree. C., Tetraglyme is in a stable condition, though it
 has a rather high vapor pressure. Also, since the above-mentioned lithium
 salt is dissolved as a solute, the organic electrolyte of the present
 invention including Tetraglyme as the main component has a higher boiling
 point than that of Tetraglyme itself due to elevation of molar boiling
 point, thereby working effectively in the high temperature environment.
 This organic electrolyte also has a favorable property in a low
 temperature environment in addition to the above-mentioned high
 temperature environment. One of the important requirements of the organic
 electrolyte battery is satisfactory discharge performance in the low
 temperature environment. Generally, solvents of high boiling point tend to
 have a high melting point and a high viscosity. Thus, such solvents make
 the conductivity of the electrolyte low in the low temperature range. If
 the temperature is lowered to -20.degree. C., for example, lithium ions of
 the organic electrolyte are prevented from moving effectively so that
 little discharge capacity can be obtained. On the contrary, Tetraglyme has
 a low melting point of -30.degree. C. although it has a high boiling point
 of 275.degree. C., and is characterized by a wide temperature range of
 about 300.degree. C. in which Tetraglyme remains in the state of solution.
 By using Tetraglyme as a solvent, the organic electrolyte can maintain the
 conductivity even under the environment of -20.degree. C. Also, the use of
 Tetraglyme as a solvent makes it possible to facilitate the movement of
 the lithium ions during discharge reaction and maintain the discharge
 capacity in a wide temperature range.
 (3) In Case Only 3-methyl Sulfolane is Used
 The organic electrolyte including an organic solvent comprising mainly
 3-methyl sulfolane is physically rather stable as a solvent at 250.degree.
 C., which is the highest temperature of the Reflow furnace, although it
 has a vapor pressure at 250.degree. C. This is because 3-methyl sulfolane
 has a boiling point of about 275.degree. C. Also, this organic electrolyte
 dissolving the above-mentioned lithium salt as a solute has a much higher
 boiling point than the highest temperature of the Reflow furnace due to
 the elevation of molar boiling point. Therefore, this organic electrolyte
 functions effectively in the manufacturing environment exposed to the high
 temperature.
 In addition to the safeguards against the high temperature atmosphere as
 described above, the organic electrolyte battery is required to have a
 satisfactory discharge performance at the temperature of not more than
 -20.degree. C. However, solvents of high boiling point have a high melting
 point and thus make the conductivity of the obtained electrolyte low in
 the low temperature range. Therefore, lithium ions are unable to move
 effectively in the organic electrolyte in the low temperature environment
 of around -20.degree. C. so that little discharge capacity can be
 obtained, actually. The 3-methyl sulfolane used in the present invention
 is characterized by the relatively low melting point of about 6.degree. C.
 in spite of the high boiling point of about 275.degree. C. Also, by
 dissolving the above-mentioned lithium salt in the solvent, the melting
 point of the electrolyte is lowered due to the depression of molar
 freezing point, which makes it possible to obtain an electrolyte having
 conductivity in the environment of -20.degree. C. Therefore, the battery
 using this organic electrolyte enables the movement of lithium during
 discharge reaction to give a good discharge capacity in the temperature
 environment of not more than -20.degree. C.
 (4) In Case Sulfolane and 3-methyl Sulforane are Used
 Sulfolane has a freezing point of 28.degree. C. When the sulfolane is used
 as a solvent of the organic electrolyte, a lithium salt as the solute
 causes the depression of freezing point to lower the freezing temperature
 of sulfolane, thus enabling the use of this electrolyte in an ordinary
 temperature range. However, this organic electrolyte cannot be used at the
 temperature of not more than -20.degree. C. Also, sulfolane has a
 relatively low conductivity in the low temperature range, which may lead
 to a large decline of discharge performance of the organic electrolyte
 battery.
 On the other hand, 3-methyl sulfolane has a freezing point of 6.degree. C.
 As described above, the depression of freezing point induced by the use of
 lithium salt contributes to the conductivity of the organic electrolyte
 even at the temperature of -20.degree. C. Therefore, the low temperature
 property of sulfolane can be improved by mixing 3-methyl sulfolane having
 a superior low temperature property with sulfolane. The mixing ratio of
 3-methyl sulfolane contained in a mixture solvent of sulfolane and
 3-methyl sulfolane is preferably 10 to 90 vol %.
 If the mixing ratio of 3-methyl sulfolnae is more than 20 volt %, effects
 of the depression of molar freezing point due to 3-methyl sulfolane are
 intensified.
 Especially, if the mixing ratio of 3-methyl sulfolnae is more than 40 volt
 %, the effects of the depression of molar freezing point due to 3-metyl
 sulfolane are further intensified. In this case, it is possible to obtain
 a large discharge capacity in the temperature range of not more than
 -20.degree. C. without deteriorating the high temperature property,
 compared to the case only 3-methyl sulfolane is used.
 The organic electrolyte including the above-mentioned mixture solvent is
 less reactive to the positive electrode and the negative electrode and is
 hardly decomposed to evolve a gas, compared to the organic electrolyte
 including Tetraglyme, and has a superior long storage characteristic.
 (5) In Case Sulfolane and Tetraglyme are Used
 As described above, when sulfolane is used as the solvent of the organic
 electrolyte, the obtained electrolyte can be used in the ordinary
 temperature range by lowering of the freezing temperature of sulfolane.
 However, this organic electrolyte cannot be used at the temperature of not
 more than -20.degree. C. Therefore, by using a mixture solvent of
 sulfolane and Tetraglyme, further improvement of the low temperature
 property can be realized.
 When Tetraglyme is mixed with sulfolane, viscosity of the organic
 electrolyte is decreased to improve absorption of the electrolyte at the
 positive electrode, so that the low temperature property is improved. On
 the other hand, the boiling point of sulfolane is about 287.degree. C. and
 the boiling point of Tetraglyme is about 275.degree. C., so their boiling
 points are higher than the internal temperature of the Reflow furnace.
 Therefore, sulfolane and Tetraglyme have a stable property against the
 high temperature atmosphere during the passage of the Reflow furnace, so
 that the organic electrolyte using the mixture solvent does not decompose
 in the high temperature environment.
 For example, the battery using the organic electrolyte with the mixing
 ratio of Tetraglyme at 5 vol % can maintain not less than 30% of the
 discharge capacity at 25.degree. C. even in the environment of not more
 than -20.degree. C. In addition, such battery never causes decline of the
 discharge performance.
 Thus, the organic electrolyte including Tetraglyme mixed with sulfolane
 makes it possible to improve the discharge performance in the low
 temperature range which can be a problem when only sulfolane is used, even
 if the ratio of Tetraglyme contained in the solvent is small.
 The mixing ratio of Tetraglyme contained in the mixture solvent of
 sulfolane and Tetraglyme is preferably 1 to 90 vol %. Particularly, the
 mixture solvent containing Tetraglyme in a range of 5 to 60 vol % provides
 an organic electrolyte battery having a superior long term reliability and
 an excellent discharge performance at a low temperature.
 However, the ratio of Tetraglyme is more than 90 vol %, the
 self-discharging rate is increased, which influences the effects obtained
 by the use of Tetraglyme, i.e. the long term reliability. With regard to
 the thermal resistance at a high temperature, there is no difference
 observed between the organic solvent comprising only Tetraglyme or
 sulfolane and the mixture solvent including sulfolane and Tetraglyme.
 (6) In Case 3-methl Sulfolane and Tetraglyme are Used
 3-methyl sulfolane has a superior property in the low temperature
 environment as well as in the high temperature environment, therefore, it
 is a solvent appropriate for the use in a wide temperature range. However,
 viscosity of 3-methyl sulfolane in an ordinary temperature range is higher
 than that of sulfolane and Tetraglyme. Thus, the battery including only
 3-methyl sulfolane as the solvent has an inferior discharge performance in
 the ordinary temperature range to the battery including sulfolane and
 Tetraglyme.
 The viscosity of 3-methyl sulfolane is lowered by adding Tetraglyme
 thereto. Then, conductivity of the organic electrolyte using this mixture
 solvent is heightened, so that the discharge performance in the ordinary
 temperature range is improved. The improvement of the conductivity is also
 observed in the low temperature environment. And, with the depression of
 the freezing point induced by dissolving the solute into 3-methyl
 sulfolane, the discharge performance in the low temperature environment
 becomes more favorable. The mixing ratio of 3-methyl sulfolane contained
 in the mixture solvent of 3-methyl sulfolane and Tetraglyme is preferably
 in a range of 10 to 90 vol %.
 (7) In Case Sulfolane, 3-methyl Sulfolane and Tetraglyme are Used
 As described above, Sulfolane and 3-methyl sulfolane have a freezing point
 of 28.degree. C. and 6.degree. C. respectively. The organic electrolyte
 battery including only these two solvents may cause a deterioration of the
 discharge performance due to the low conductivity of the solvents in the
 low temperature range. However, if Tetraglyme is added to the mixture
 solvent of sulfolane and 3-methyl sulfolane, viscosity of the electrolyte
 is decreased to improve absorption of the electrolyte by the positive
 electrode, so that the low temperature property may be further improved.
 The mixing ratio of Tetraglyme contained in the mixture solvent comprising
 sulfolane, 3-metyl sulfolane and Tetraglyme is preferably in a range of 1
 to 90 vol %. Particularly, if the ratio of Tetraglyme is in a range of 5
 to 60 vol %, it is possible to provide a battery with a long term
 reliability and a superior discharge performance at the low temperature.
 However, if the ratio of Tetraglyme is more than 90 vol %, the
 self-discharging rate is increased, influencing the effects obtained by
 the use of sulfolane and 3-methyl sulfolane, that is, the long term
 reliability. As per thermal resistance at a high temperature, there is no
 difference observed between the organic solvent comprising only Tetraglyme
 and the mixture solvent including sulfolane, 3-methyl sulfolane and
 Tetraglyme.
 As described above, the solvent constituting the organic electrolyte of the
 present invention contains at least one selected from the group consisting
 of Tetraglyme, sulfolane and 3-methyl sulfolane as the main component. But
 the solvent of the present invention may contain other conventional
 solvents such as ethylene carbonate, propylene carbonate, butylene
 carbonate and .gamma.-butylolactone in a range where the effects of the
 present invention are not deteriorated. The mixing ratio of these
 conventional solvents contained in the organic solvent of the present
 invention should be 0.1 to 30 vol %. Preferably, the ratio is 0.3 to 10
 vol %.
 Next, explanation will be given for the other battery components of the
 present invention.
 The gasket also has a function as an insulating packing to insulate the
 positive can and the negative can and is fabricated by injection molding
 into a shape to fit an internal surface of the positive can. The separator
 is preferably made of nonwoven fabric of polyphenylene sulfide. Also, a
 paper separator of cellulose can be substituted for this separator.
 Polyphenylene sulfide used for the separator and the gasket of the present
 invention has been selected from the viewpoint of stability against the
 electrolyte as well as thermal resistance. Polyphenylene sulfide has a
 thermosoftening temperature of not less than 200.degree. C. and is free
 from heat distortion at the temperature of about 250.degree. C., if a
 filler such as glass fiber is added. It is thus possible to maintain each
 function of the gasket and the separator in the high temperature
 environment of the Reflow furnace. Cellulose also has the same effects as
 described above.
 Also, polyphenylene sulfide is not soluble in any of the solvents of
 Tetraglyme, sulfolane and 3-methyl sulfolane used for the organic
 electrolyte of the present invention, thus having a chemically stability.
 This stability of polyphenylene sulfide makes it possible to obtain a long
 term reliability.
 Further, in the present invention, it is preferable that a sealant made of
 at least one selected from a group consisting of isobutylene-isoprene
 rubber, styrene-butadiene rubber and fluorocarbon resin of which a part of
 the side chains is substituted with a silicon resin is disposed at a
 portion where the above-mentioned gasket is in contact with the
 above-mentioned positive can and negative can.
 Conventionally, pitch has been used as a sealant of the organic electrolyte
 battery. Pitch is inexpensive and effective in sealing, but lacks thermal
 resistance. Since pitch melts to liquid in the environment of about
 250.degree. C., sealing effects cannot be obtained. On the other hand, the
 above-mentioned gasket of the present invention has a high thermal
 resistance. Therefore, when the gasket is caused to pass the Reflow
 furnace, the gasket has little dimensional deformation due to heat so that
 excellent sealing effects can be maintained.
 The sealant is required to have properties appropriate for the use as a
 sealant. As described above, the sealant is placed between the gasket and
 the positive/negative can. Between the gasket and the positive/negative
 can, exists an extremely small space. The size of such space is varied
 microscopically according to the condition of the surface of the
 positive/negative can and the gasket and is not uniform over the sealing
 portion of the battery case. The sealant is intended to seal or close the
 above-mentioned space, so it is required that the sealant is deformable
 according to the dimensional change of the space and is able to be firmly
 adhered to the positive/negative can and the gasket.
 For such requirements of the sealant, Mooney viscosity and unsaturation
 ratio should be preferably applied to the evaluation criteria for the
 properties of isobutylene-isoprene rubber and styrene-butadiene rubber.
 Mooney viscosity is a fundamental figure of representing rubber strength.
 Mooney viscosity is the numerically represented resistance obtained when
 shearing force is applied at a certain temperature to a rubber between two
 discs. Meanwhile, the unsaturation ratio means a ratio of sites having a
 double bond in a molecular structure. As this value increases, adhesion
 property improves.
 Another property required for the sealant is chemical stability against the
 organic electrolyte. The sealant is disposed on the surface of the gasket
 and is in contact with the organic electrolyte in the battery case.
 Therefore, the sealant is required to have the chemical stability which
 prevents the sealant from being decomposed by the organic electrolyte and
 giving adverse effects on the organic electrolyte, as well as the thermal
 resistance described above. The organic electrolyte of the present
 invention does not dissolve the above-mentioned sealant and the battery
 configured by using the above-mentioned electrolyte and the sealant causes
 no leakage.
 As regards the sealant of the present invention, isobutylene-isoprene
 rubber is a copolymer of isobutylene and isoprene, and for example, the
 isobutylene-isoprene rubber represented by the chemical formula (1):
 ##STR1##
 wherein m=3, n=97 may be used for the present invention. Especially, it is
 preferable in terms of mechanical properties to use the
 isobutylene-isoprene rubber having a Mooney viscosity at 100.degree. C. of
 20 to 100 and an unsaturation ratio of 0.1 to 5 mol %. Moreover, it is
 most appropriate to use the isobutylene-isoprene rubber having a Mooney
 viscosity of 30 to 80 and an unsaturation ratio of 0.5 to 3.5 mol %.
 Also, as the styrene-butadiene rubber, the styrene-butadiene rubber, which
 is a copolymer of styrene and butadiene, may be represented by the
 chemical formula (2):
 ##STR2##
 wherein x=1, y=6. Especially, it is preferable in terms of mechanical
 properties to use the styrene-butadiene rubber having a Mooney viscosity
 at 100.degree. C. of 20 to 150 and an unsaturation ratio of 8 to 20 mol %.
 Moreover, it is most appropriate to use the styrene-butadiene rubber
 having a Mooney viscosity of 35 to 75 and an unsaturation ratio of 10 to
 18 mol %. Also, weight ratio of styrene/butadiene constituting the
 styrene-butadiene rubber is preferably 20/80 to 35/65.
 Further, as the fluorocarbon resin of which a part of the side chains is
 substituted with a silicon resin, for example, the fluorocarbon resin
 represented by the chemical formula (3):
 ##STR3##
 may be used for the present invention.
 Furthermore, as the fluorocarbon resin, for example, TFE-propylene of
 fluorocarbon resin represented by the chemical formula (4):
 ##STR4##
 or VDF of fluorocarbon resin represented by the chemical formula (5):
 ##STR5##
 is preferably used for the present invention.
 The sealant of the present invention, being dissolved in a volatile organic
 solvent, is applied to the gasket or the positive/negative can. The
 volatile organic solvents used for the present invention include volatile
 solvents of a low boiling point such as methylethyl ketone, xylene,
 chloroform, dichloroethane, dichloromethane, toluene, cyclohexane and
 petroleum ether. From these volatile solvents, an appropriate solvent can
 be selected according to the kind of the sealant used. Also, mixing ratio
 by weight of the above-mentioned sealant to the volatile organic solvent
 is 0.1/99.9 to 20/80, preferably 1/99 to 10/90.
 As described above, the organic electrolyte battery in accordance with the
 present invention has succeeded in obtaining enough thermal resistance to
 withstand the high temperature of about 250.degree. C. by combination of
 the power generating elements and the sealant having a high thermal
 resistance at a high temperature. Therefore, it is possible to mount the
 battery of the present invention onto a substrate by the automatic
 soldering according to the Reflow method.
 EXAMPLES
 Experiment 1
 FIG. 1 shows a schematic longitudinal sectional view of an organic
 electrolyte battery fabricated for this experiment in accordance with the
 present invention. The battery has a diameter of 6.8 mm and a thickness of
 2.1 m. For a positive can 1 to serve as a positive terminal and a negative
 can (occasionally referred to as "seal plate") 2 to serve as a negative
 terminal, stainless steel having a superior corrosion resistance was used.
 A gasket 3 insulating the positive can 1 and the negative can 2 was made
 of PPS. Pitch was applied to the surface of the gasket 3 which was in
 contact with the positive can and the negative can. The positive electrode
 4 was prepared as follows. An active material lithium manganate was mixed
 with carbon black as a conductive agent and a powder of fluorocarbon resin
 as a binder, and the mixture was molded to a pellet of 4 mm in diameter
 and 1.2 mm in thickness, followed by drying at 250.degree. C. for 12
 hours. The negative electrode 5 was formed by punching out an
 aluminum-manganese alloy containing metallic manganese in a weight ratio
 of 5% into a disc of 4 mm in diameter and 0.3 mm in thickness and was
 provided inside of the negative can 2.
 Also, in assembling the battery, a metallic lithium foil was pressurized
 and adhered onto the surface of the aluminum alloy, and lithium was then
 absorbed in the presence of an electrolyte into the aluminum alloy to
 electrochemically produce a lithium-aluminum alloy. This was used as the
 negative electrode. A carbon film 7 to serve as a current collector was
 formed on the middle of the inside of the positive can 1, and the positive
 electrode 4 and a separator 6 made of PPS nonwoven fabric were mounted on
 top of the carbon film. Then, after charging the electrolyte, the negative
 can 2 provided with the negative electrode 5 and the gasket 3 was jointed
 with the positive can 1, and the opening end of the positive can was
 fastened to the periphery of the gasket to seal the battery.
 The electrolyte used for the battery of the above-described configuration
 included as a lithium salt lithium bisperfluoromethyl sulfonyl imide
 dissolved at a concentration of 1 mol/l in a mixture solvent containing
 sulfolane and propylene carbonate in a volumetric ratio of 5:1. This
 electrolyte of 15 .mu.l was charged to the battery, which was named A-1.
 Also, another battery named A-2 was produced in the same manner as the
 battery A-1 except for the use of lithium trifluoromethanesulfonate as a
 lithium salt.
 For comparison, a battery A-3 was produced in the same manner as the
 battery A-1 except for the use of propylene carbonate as a solvent.
 Also, for comparison, another battery A-4 was produced in the same manner
 as the battery A-1 except for the use of a mixture solvent containing
 sulfolane and 1,2-dimethoxy ethane in a volumetric ratio of 2:1
 Further, for comparison, still another battery A-5 was produced in the same
 manner as the battery A-1 except for the use of lithium
 hexafluorophosphate as a lithium salt.
 Furthermore, for comparison, another battery A-6 was produced in the same
 manner as the battery A-1 except for the use of lithium perchlorate as a
 lithium salt.
 Next, a battery A-7 was produced in the same manner as the battery A-1
 except for the use of a separator made of polypropylene nonwoven fabric.
 Thereafter, a battery A-8 was produced in the same manner as the battery
 A-1 except for the use of a gasket made of polypropylene.
 Finally, a battery A-9 was produced in the same manner as the battery A-1
 except for the use of a solvent containing only sulfolane.
 [Evaluation]
 The initial internal resistance (Alternating current anodizing method; 1
 kHz) of the batteries thus produced A-1 to A-9 was examined, then
 discharge capacity was measured at 20.degree. C., with the load of 100
 k.OMEGA. connected. The discharge capacity was obtained, based on the
 ratio against the theoretical capacity of lithium manganate which was
 defined as 100. Next, with a constant current of 0.1 mA, charge/discharge
 cycle test was performed by setting the upper limit of voltage at 3.25 V
 and the lower limit at 2.0 V, to obtain the maximum number of
 charge/discharge cycle.
 Thereafter, each of the batteries was actually caused to pass a high
 frequency heating Reflow furnace to perform a Reflow furnace passage
 resistance test. The temperature profile of the Reflow furnace test
 comprised a preliminary heating process of 180.degree. C. for 2 minutes, a
 heating process of 180.degree. C. for 30 seconds, 245.degree. C. for 30
 seconds and 180.degree. C. for 30 seconds and a natural cooling process to
 cool to room temperature. The batteries were caused to pass the furnace
 three times altogether, while being subjected to visual inspection and
 voltage examination. After that, the internal resistance of these
 batteries was measured again, and the value obtained was compared to the
 initial value to examine the degree of deterioration of the batteries.
 Table 1 shows the combination of battery constituting components and Table
 2 lists the results of the test.
 TABLE 1
 Solvent Lithium salt Separator
 Gasket
 A-1 Sulfolane Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 Propylene carbonate
 A-2 Sulfolane Lithium trifluoromethanesulfonate PPS
 PPS
 Propylene carbonate
 A-3 Propylene carbonate Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 A-4 Sulfolane Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 1,2-dimethoxyethane
 A-5 Sulfolane Lithium hexafluorophosphate PPS
 PPS
 Propylene carbonate
 A-6 Sulfolane Lithium perchlorate PPS
 PPS
 Propylene carbonate
 A-7 Sulfolane Lithium bisperfluoromethyl sulfonyl imide PP
 PPS
 Propylene carbonate
 A-8 Sulfolane Lithium bisperfluoromethyl sulfonyl imide
 PPS PP
 Propylene carbonate
 A-9 Sulfolane Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 TABLE 2
 Initial Condition after passage
 of the
 internal Discharge Charge/discharge Reflow furnace
 Internal resistance
 resistance capacity cycle First Second
 Third after the Reflow test
 Battery (.OMEGA.) (%) (times) passage passage
 passage (.OMEGA.)
 A-1 150 94 85 Good Good
 Good 156
 A-2 245 91 43 Good Good
 Good 255
 A-3 147 95 86 Exploded --
 -- --
 A-4 95 98 84 Exploded --
 -- --
 A-5 240 91 47 Good Good
 Good 2900
 A-6 654 62 35 Good Good
 Good 1200
 A-7 137 95 87 Short- --
 -- --
 circuited
 A-8 152 95 83 Leaked --
 -- --
 A-9 260 93 78 Good Good
 Good 265
 According to Table 2, the battery A-1 of the present invention had
 discharge capacity of 94% of the theoretical value and showed no
 abnormality after the Reflow furnace passage test was performed three
 times. Also, the internal resistance remained almost unchanged even after
 the passage of the furnace. This means that the battery was free from
 thermal damage due to the passage of the Reflow furnace and gave a
 favorable result. The battery A-2 using lithium trifluoromethanesulfonate
 as a lithium salt showed neither abnormality nor trouble after the test
 was repeated three times and gave a favorable result in terms of
 electrical properties just like the result of the battery A-1. But the
 battery A-2 showed a little higher initial internal resistance than the
 battery A-1. The battery A-9 also showed a good condition after the
 passage of the furnace and had favorable electrical properties, although
 the battery had a little higher initial internal resistance just like the
 battery A-2.
 On the other hand, the comparative battery A-3 using propylene carbonate as
 a solvent exploded, presumably because of the increased internal pressure
 caused by the boiling of the solvent during the passage of the Reflow
 furnace. Also, the comparative battery A-4 including 1,2-dimethoxy ethane,
 which had a low viscosity and a low boiling point, showed the least
 internal resistance, but exploded during the passage of the furnace,
 presumably because of the same reason as the battery A-3. The comparative
 battery A-5 including lithium hexafluorophosphate as a lithium salt and
 the battery A-6 including lithium perchlorate both showed an increased
 internal resistance. This is considered due to the increased electrolyte
 resistance induced by thermal decomposition of the lithium salt after the
 passage of the furnace. As a result, electrical properties of these
 batteries were destroyed as described.
 Further, the battery A-7 using polypropylene as a material of a separator,
 was short-circuited internally because the separator melted and shrank
 during the passage of the furnace, bringing the negative electrode into
 contact with the positive electrode. The battery A-8 using polypropylene
 for a gasket produced a leakage from molten portions because of melting of
 the gasket during the passage of the furnace. As per the number of
 charge/discharge cycle, regardless of the type of the solvent, the
 electrolytes including lithium bisperfluoromethyl sulfonyl imide as a
 lithium salt gave favorable results with not less than 80 cycles of
 charge/discharge, compared to the electrolytes including other lithium
 salts. The reason is considered to be that lithium bisperfluoromethyl
 sulfonyl imide had a good effect on the form of lithium deposition on the
 surface of the lithium-aluminum alloy of the negative electrode.
 As described above, the batteries in accordance with the present invention
 had excellent results in any of the discharge performance, the
 charge/discharge cycle performance and the high thermal resistance at a
 high temperature during the passage of the Reflow furnace. This is because
 of the thermal resistance of sulfolane which is the main component of the
 solvent of the electrolyte and the thermal resistance, the superior
 conductivity and the stability for the lithium-aluminum alloy negative
 electrode of lithium bisperfluoromethyl sulfonyl imide as a lithium salt.
 This is also because of the obtainment of the thermal resistance to
 withstand the high temperature of the Reflow furnace enabled by the use of
 polyphenylene sulfide for the battery components, gasket and the
 separator. Also, when lithium bisperfluoroethyl sulfonyl imide was used as
 a lithium salt, the similar results to the above could be obtained.
 Experiment 2
 Also hereinafter, the battery of the configuration described in FIG. 1 was
 produced.
 The electrolyte used in this experiment included lithium bisperfluoromethyl
 sulfonyl imide dissolved in 3-methyl sulfolane at a concentration of 1
 mol/l. Except for the use of this electrolyte of 15 .mu.l, a battery B-1
 was produced in the same manner as the battery A-1.
 A battery B-2 was produced in the same manner as the battery B-1 except for
 the use of lithium bisperfluoroethyl sulfonyl imide as a lithium salt.
 A battery B-3 was produced in the same manner as the battery B-1 except for
 the use of lithium trifluoromethanesulfonate as a lithium salt.
 A battery B-4 was produced in the same manner as the battery B-1 except for
 the use of a mixture solvent containing 3-methyl sulfolane and sulfolane
 in a volumetric ratio of 2:1.
 A battery B-5 was produced in the same manner as the battery B-1 except for
 the use of a separator made of cellulose.
 A battery B-6 was produced in the same manner as the battery B-1 except for
 the use of propylene carbonate as the solvent.
 A battery of B-7 was produced in the same manner as the battery B-1 except
 for the use of lithium hexafluorophosphate as a lithium salt.
 A battery of B-8 was produced in the same manner as the battery B-1 except
 for the use of a separator made of polypropylene.
 A battery of B-9 was produced in the same manner as the battery B-1 except
 for the use of a gasket made of polypropylene.
 [Evaluation]
 The batteries B-1 to B-9 thus produced were evaluated in the same manner as
 the Experiment 1, except that discharge capacity was measured at
 20.degree. C. with the load of 100 k.OMEGA. connected and measured at
 -20.degree. C. with the load of 300 k.OMEGA., and the discharge capacity
 was obtained.based on the ratio against the theoretical capacity of
 lithium manganate which was defined as 100. The batteries were caused to
 pass the Reflow furnace twice. Table 3 shows the combination of the
 battery constituting components. Table 4 lists the results.
 TABLE 3
 Solvent Lithium salt Separator
 Gasket
 B-1 3-methyl sulfolane Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 B-2 3-methyl sulfolane Lithium bisperfluoroethyl sulfonyl imide PPS
 PPS
 B-3 3-methyl sulfolane Lithium trifluoromethanesulfonate PPS
 PPS
 B-4 3-methyl sulfolane Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 Sulfolane
 B-5 3-methyl sulfolane Lithium bisperfluoromethyl sulfonyl imide
 Cellulose PPS
 B-6 Propylene carbonate Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 B-7 3-methyl sulfolane Lithium hexafluorophosphate PPS
 PPS
 B-8 3-methyl sulfolane Lithium bisperfluoromethyl sulfonyl imide PP
 PPS
 B-9 3-methyl sulfolane Lithium bisperfluoromethyl sulfonyl imide
 PPS PP
 TABLE 4
 Initial Discharge Condition after
 passage
 internal Capacity of the Reflow
 furnace Internal resistance
 resistance (%) Charge/discharge First
 Second after the Reflow test
 Battery (.OMEGA.) 20.degree. C. -20.degree. C. Cycle (times)
 passage passage (.OMEGA.)
 B-1 160 94 68 85 Good
 Good 172
 B-2 165 91 62 83 Good
 Good 179
 B-3 256 82 43 56 Good
 Good 282
 B-4 158 95 81 84 Good
 Good 185
 B-5 152 94 69 80 Good
 Good 169
 B-6 120 98 91 82 Exploded
 -- --
 B-7 169 93 67 65 Good
 Good 4990
 B-8 158 95 68 83 Short-
 -- --
 circuited
 B-9 159 93 65 84 Leaked
 -- 8200
 According to Table 4, the battery B-1 had discharge capacity of 94% of the
 theoretical value and showed no abnormality after the Reflow furnace
 passage test was performed twice. Also, the internal resistance remained
 almost unchanged even after the passage of the furnace. This means that
 the battery was free from thermal damage due to the passage of the Reflow
 furnace and was a favorable battery. The battery B-2 using lithium
 bisperfluoroethyl sulfonyl imide as a lithium salt produced the similar
 favorable result to the battery B-1.
 The battery B-3 using lithium trifluoromethanesulfonate showed an increased
 initial internal resistance and a little shortened charge/discharge cycle
 life, compared to the battery B-1. However, this was not so bad as to
 cause a problem in practical use. The battery B-3 showed no abnormality
 after the Reflow test was done twice just like the result of the battery
 B-1, and gave a favorable result in the electrical properties. The battery
 B-4 using the mixture solvent containing 3-methyl sulfolane and sulfolane
 in a volumetric ratio of 2:1 also gave a favorable result in the
 electrical properties, the discharge performance and the condition after
 the passage of the Reflow furnace.
 Also, the battery B-4 had 81% of the positive electrode discharge capacity
 at -20.degree. C., the highest among the batteries, showing a favorable
 discharge performance. This is considered because the use of the mixture
 solvent lowered the freezing point of the electrolyte due to depression of
 the molar freezing point, elevated the conductivity of the electrolyte and
 facilitated the movement of the lithium ions in discharging.
 The battery B-5 using the separator made of cellulose gave a favorable
 result just like the battery B-1 using the separator made of PPS nonwoven
 fabric.
 The battery B-6 using propylene carbonate as a solvent exploded during the
 passage of the Reflow furnace, presumably due to the increased internal
 pressure induced by boiling of the solvent.
 The Battery B-7 using lithium hexafluorophosphate as a lithium salt had an
 increased internal resistance. This is considered because of the increased
 electrolyte resistance induced by thermal decomposition of the lithium
 salt after the passage of the Reflow furnace. Thus, the electrical
 properties of this battery were deteriorated.
 The Battery B-8 using the separator made of polypropylen was
 short-circuited internally because the separator melted and shrank during
 the passage of the furnace, bringing the negative electrode into contact
 with the positive electrode. Thus, the battery function was deteriorated.
 The battery B-9 using the gasket made of polypropylen produced a leakage
 from molten portions because of melting of the gasket during the passage
 of the furnace.
 As per the number of charge/discharge cycle, regardless of the type of the
 solvent, the electrolytes including lithium bisperfluoromethyl sulfonyl
 imide and lithium bisperfluoroethyl sulfonyl imide as a lithium salt gave
 favorable results with not less than 80 cycles of charge/discharge,
 compared to the electrolytes including other lithium salts. This is
 considered because lithium bisperfluoromethyl sulfonyl imide and lithium
 bisperfluoroethyl sulfonyl imide had a good effect on the form of lithium
 deposition on the surface of the lithium-aluminum alloy of the negative
 electrode.
 As described above, it was confirmed that the batteries in accordance with
 the present invention had excellent results in any of the discharge
 performance, the charge/discharge cycle performance and the high
 temperature resistance during the passage of the Reflow furnace. This is
 because of the thermal resistance of 3-methyl sulfolane which is the main
 component of the solvent of the electrolyte and the thermal resistance,
 the superior conductivity and the stability for the lithium-aluminum alloy
 negative electrode of lithium salts. This is also because of the
 obtainment of the thermal resistance to withstand the high temperature of
 the Reflow furnace enabled by the use of the gasket made of PPS, as well
 as the separator made of PPS nonwoven fabric or cellulose, as the battery
 component.
 Also, the use of the mixture solvent containing 3-methyl sulfolane and
 sulfolane as the solvent enabled the batteries to obtain a further
 superior low temperature discharge performance.
 Experiment 3
 Also in this experiment, the battery of the configuration described in FIG.
 1 was produced.
 The electrolyte used in this experiment included lithium bisperfluoromethyl
 sulfonyl imide of a solute dissolved in Tetraglyme as a solvent at a
 concentration of 1 mol/l. Except that this electrolyte of 15 .mu.l was
 charged to a battery case comprising the positive can 1, the negative can
 2 and the gasket 3, in the same manner as the battery A-1, a battery C-1
 was produced.
 A battery C-2 was produced in the same manner as the battery C-1 except for
 the use of lithium trifluoromethansulfonate as a lithium salt.
 A battery C-3 was produced in the same manner as the battery C-1 except for
 the use of a mixture solvent containing Tetraglyme and sulfolane in a
 volumetric ratio of 6:4.
 Also, a battery C-3' was produced in the same manner as the battery C-1
 except for the use of a mixture solvent containing Tetraglyme and 3-methyl
 sulfolane in a volumetric ratio of 6:4.
 A battery C-4 was produced in the same manner as the battery C-1 except for
 the use of a mixture solvent containing Tetraglyme, 3-methyl sulfolane and
 sulfolane in a volumetric ratio of 3:1:1.
 A battery C-5 was produced in the same manner as the battery C-1 except for
 the use of a separator made of cellulose.
 For comparison, a battery C-6 was produced in the same manner as the
 battery C-1 except for the use of propylene carbonate as a solvent.
 A battery C-7 was produced in the same manner as the battery C-1 except for
 the use of lithium hexafluorophosphate as a lithium salt.
 A battery C-8 was produced in the same manner as the battery C-1 except for
 the use of a separator made of polypropylene.
 A battery C-9 was produced in the same manner as the battery C-1 except for
 the use of a gasket made of polypropylene.
 [Evaluation]
 The batteries thus obtained, C-1 to C-9, were evaluated in the same manner
 as the Experiment 1 with the following exceptions. The discharge capacity
 was measured at 20.degree. C. with the load of 100 k.OMEGA. connected and
 with a constant current of 0.1 mA, charge/discharge cycle test was
 performed by setting the upper limit of voltage at 3.25 V and the lower
 limit at 2.0 V, to obtain maximum number of charge/discharge cycle. The
 discharge capacities were based on the ratio against the theoretical
 capacity of lithium manganate which was defined as 100. Table 5 shows the
 combination of the battery components and Table 6 shows the results.
 TABLE 5
 Solvent Lithium salt Separator
 Gasket
 C-1 Tetraglyme Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 C-2 Tetraglyme Lithium trifluoromethanesulfonate PPS
 PPS
 C-3 Tetraglyme Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 Sulfolane
 C-3' Tetraglyme Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 3-methyl sulfolan
 C-4 Tetraglyme Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 3-methyl sulfolan
 Sulfolane
 C-5 Tetraglym Lithium bisperfluoromethyl sulfonyl imide
 Cellulose PPS
 C-6 Propylene carbonate Lithium bisperfluoromethyl sulfonyl imide
 PPS PPS
 C-7 Tetraglym Lithium hexafluorophosphate PPS
 PPS
 C-8 Tetraglym Lithium bisperfluoromethyl sulfonyl imide PP
 PPS
 C-9 Tetraglym Lithium bisperfluoromethyl sulfonyl imide
 PPS PP
 TABLE 6
 Initial Condition after passage
 of the
 internal Discharge Charge/discharge Reflow furnace
 Internal resistance
 resistance capacity cycle First Second
 Third after the Reflow test
 Battery (.OMEGA.) (%) (times) passage passage
 passage (.OMEGA.)
 C-1 180 93 88 Good Good
 Good 175
 C-2 205 85 75 Good Good
 Good 185
 C-3 223 92 90 Good Good
 Good 220
 C-3' 290 89 70 Good Good
 Good 330
 C-4 247 94 93 Good Good
 Good 243
 C-5 214 93 86 Good Good
 Good 217
 C-6 100 100 100 Exploded --
 -- --
 C-7 145 92 64 Good Good
 Good 1450
 C-8 198 93 48 Short- --
 -- --
 circuited
 C-9 175 93 88 Leaked --
 -- --
 According to Table 6, the battery C-1 had discharge capacity of 93% of the
 theoretical value and showed no abnormality after the Reflow furnace
 passage test was repeated three times. Also, the internal resistance
 remained almost unchanged even after the passage of the furnace. This
 means that the battery was free from thermal damage due to the passage of
 the Reflow furnace and produced a favorable result. The battery C-2 using
 lithium trifluoromethanesulfonate as a lithium salt had a higher initial
 internal resistance value than that of the battery C-1. However, the
 battery C-2 showed no abnormality after the Reflow test was repeated three
 times just like the battery C-1 and gave a favorable result of the
 electrical properties.
 The battery C-3 and C-3' had a high initial internal resistance, because
 the use of the mixture solvent containing sulfolane or 3-methyl sulfolane
 in a volumetric ratio of 40% lead to an increase in electrolyte viscosity.
 However, the battery C-3 and C-3' gave a favorable result in terms of the
 charge/discharge viscosity, compared to the battery C-1, and also showed
 no abnormality in the Reflow furnace passage test. The battery C-4 to
 which sulfolane and 3-methyl sulfolane were further added showed a further
 improved result in terms of the electrical properties compared to the
 battery C-3, because the amount of Tetraglyme contained in the electrolyte
 was decreased.
 The battery C-5 had a high initial internal resistance compared to the
 battery C-1, but except this, gave a favorable result.
 Contrary to these results, the battery C-6 exploded, because propylene
 carbonate used as a solvent boiled, thereby inducing the increased
 pressure. Also, the battery C-7 had an increased internal resistance of
 the electrolyte, because lithium hexafluorophosphate used as a lithium
 salt was thermally decomposed during the passage of the furnace. This
 means the increased internal resistance and shows that the electrical
 properties of the battery were destroyed.
 The battery C-8 showed shrinkage of the separator and was short-circuited
 internally. This is because polypropylene used for the separator was
 exposed to a temperature higher than the melting temperature during the
 passage of the furnace and thereby the separator melted and shrank,
 bringing the negative electrode into contact with the positive electrode.
 The battery C-9 showed a leakage from the gasket made of polypropylene.
 This is because the gasket shrank and melted due to the same phenomenon as
 the battery C-8, thus causing the leakage from the molten portion of the
 gasket.
 As per the number of charge/discharge cycle, regardless of the type of the
 solvent, the batteries including lithium bisperfluoromethyl sulfonyl imide
 as a solute gave favorable results with batteries not less than 80 cycles
 of charge/discharge, compared to the batteries including other lithium
 salts. This is considered because lithium bisperfluoromethyl sulfonyl
 imide had a good effect on the form of lithium deposition on the surface
 of the lithium-aluminum alloy of the negative electrode.
 As described above, it was confirmed that the batteries in accordance with
 the present invention had excellent results in any of the discharge
 performance, the charge/discharge cycle performance and the high
 temperature resistance during the passage of the Reflow furnace. This is
 because of the thermal resistance of Tetraglyme which is the main
 component of the solvent of the electrolyte and the thermal resistance,
 the conductivity and the stability for the lithium-aluminum alloy negative
 electrode of lithium bisperfluoromethyl sulfonyl imide of the solute. The
 similar results could be obtained when lithium bisperfluoroethyl sulfonyl
 imide was used as a solute.
 Further, the use of polyphenylene sulfide for the separator and the gasket
 makes it possible to obtain the stability against the above-mentioned
 organic electrolyte as well as the thermal resistance during the passage
 of the Reflow furnace.
 Experiment 4
 Batteries C-10 to C-16 were produced in the same manner as the battery C-1,
 except for the use of a mixture solvent containing Tetraglyme and
 sulfolane in the mixing ratio shown in Table 7. For these batteries,
 lithium manganate was used for the positive electrode, a lithium-aluminum
 alloy for the negative electrode and polyphenylene sulfide for a gasket
 and a separator.
 The Reflow furnace passage test was performed by causing the batteries to
 pass the inside of the high frequency heating Reflow furnace, to examine
 high temperature resistance of the batteries C-10 to C-16. For this test,
 the batteries were caused to pass the furnace twice in the same
 temperature profile as that of the Experiment 1. After the test,
 occurrence of explosion and leakage was observed by visual inspection, but
 any of the batteries C-10 to C-16 produced neither leakage nor explosion.
 Subsequently, using the batteries having been subjected to the Reflow
 furnace test, discharge test was conducted with these batteries connected
 to resistance of 300 k.OMEGA. under an environment of -20.degree. C. Also,
 using the batteries having been subjected to the Reflow test, after they
 were stood in a thermostat of 60.degree. C. for 100 days, another
 discharge test was conducted with these batteries connected to resistance
 of 51 k.OMEGA. at room temperature. Based on the measurements of discharge
 capacity obtained by these discharge tests, the ratio against the
 theoretical capacity was obtained in the same manner as the Experiment 3.
 Table 7 shows the results. Further, self-discharging rate was obtained
 based on the discharge capacity before and after the storage of 100 days.
 Table 7 also shows this result.
 TABLE 7
 Evaluation results
 Self-
 Composition of a mixture Discharge Remaining discharging
 Battery solvent (vol %) capacity capacity rate
 C Tetraglyme Sulfolane (%) (%) (%)
 10 -- 100 0.1 95 5
 11 1 99 10 92 8
 12 5 95 31 90 10
 13 60 40 55 88 12
 14 90 10 60 83 17
 15 92 8 62 70 30
 16 100 -- 70 59 41
 According to Table 7, the battery C-10 using only sulfolane as a solvent
 hardly discharged in the environment of -20.degree. C. This is considered
 because the electrolyte itself froze. On the other hand, as per the
 batteries C-11 to C-16 containing Tetraglyme, the discharge capacity in
 the low temperature environment increased, as the ratio of Tetraglyme
 contained in a solvent increased. Especially, the battery C-1 using only
 Tetraglyme as a solvent showed the most favorable result in terms of the
 discharge capacity in this environment. From these, it has been discovered
 that when sulfolane is only used as a solvent of an electrolyte, the
 electrolyte freezes at -20.degree. C., but that if Tetraglyme is added to
 the solvent, the electrolyte of such solvent does not freeze so that
 discharging in the low temperature environment is possible. In this case,
 Tetraglyme is also considered to have an effect of improving the
 conductivity of the electrolyte itself.
 On the other hand, from the viewpoint of the reliability in long term
 storage, the battery C-10 using only sulfolane is preferable. The battery
 C-16 using the solvent comprising onlly Tetraglyme showed a high
 self-discharging rate of not less than 40%. The increasing rate of the
 self-discharging rate changed at 90% of the volumetric ratio of Tetraglyme
 contained in a solvent, and the self-discharging rate of the batteries of
 C-15 and C-16 containing Tetraglyme in a higher ratio than 90% sharply
 multiplied. On the contrary, regarding the batteries C-10 to C-14
 containing Tetraglyme in a volumetric ratio of not more than 90%, the
 self-discharging rate decreased, as the ratio of sulfolane increased.
 Especially, the battery C-10 using only sulfolane as a solvent showed a
 low self-discharging rate of 5%, having an excellent reliability in long
 term storage. Therefore, it can be concluded that the battery containing
 sulfolane mainly as a solvent has a small self-discharging rate compared
 to the battery containing Tetraglyme mainly.
 From the viewpoint of the battery performance required for the organic
 electrolyte battery such as discharge performance in a low temperature
 environment and reliability in long term storage, the mixture solvent of
 sulfolane and 3-methyl sulfolane is preferable to the solvent containing
 Tetraglyme. Particularly, the mixture solvent containing Tetraglyme in a
 mixing ratio of not more than 90% as well as sulfolane and 3-methyl
 sulfolane is preferable in terms of the battery performance.
 Also, the batteries which needs reliability in long term storage more than
 discharge performance in a low temperature environment, for example, the
 batteries to be used in a room temperature environment mainly for memory
 back-up power source of various appliances, should preferably contain
 Tetraglyme in a solvent in a ratio of 5 to 60%.
 In this experiment, the use of the solvent containing 3-methyl sulfolane as
 well as Tetraglyme also made it possible to obtain the battery having both
 discharge performance in the low temperature environment and reliability
 during long term storage.
 Experiment 5
 In this experiment, a coin-shaped organic electrolyte battery of the
 configuration described in FIG. 1 was produced. A positive can 1 of
 stainless steel was combined with a negative can (or a seal plate) 2 so as
 to form a battery case of 6.8 mm in diameter and 2.1 mm in thickness. PPS
 was used for a gasket 3 to be inserted between the positive can 1 and the
 negative can 2. Isobutylene-isoprene rubber diluted with toluene was used
 for a sealant (not illustrated in FIG. 1) to be placed between the gasket
 3 and the positive can 1 and between the negative can 2 and the gasket 3,
 and was applied to the gasket, which was then placed at a predetermined
 position.
 A positive electrode 4 was prepared as follows. An active material lithium
 manganate was mixed with carbon black as a conductive agent and a powder
 of fluorocarbon resin as a binder, and the mixture was molded to a pellet
 of 4 mm in diameter and 1.2 mm in thickness, followed by drying at
 250.degree. C. for 12 hours. The pellet-shaped positive material thus
 obtained was mounted onto a positive current collector 7 formed by
 applying carbon paint on the internal surface of the positive can 1.
 Meanwhile, a negative electrode 5 was produced as follows. An
 aluminum-manganese alloy containing manganese in a weight ratio of 5% was
 punched out into a disc of 4 mm in diameter and 0.3 mm in thickness and
 the disc of the alloy was provided inside of the positive can 2.
 Also, in assembling the battery, a metallic lithium foil was pressurized
 and adhered onto the aluminum alloy, and lithium was then absorbed in the
 presence of an electrolyte into the aluminum alloy to electrochemically
 produce a lithium-aluminum alloy. The alloy thus obtained was used as the
 negative electrode 5.
 For a separator 6 to be placed between the positive electrode 4 and the
 negative electrode 5, PPS was used just like the gasket. For an
 electrolyte, a lithium salt was dissolved as a solute in sulfolane of an
 organic solvent. The electrolyte of 10 .mu.l was charged to a battery
 case. The battery thus obtained was named D-1 of this experiment.
 A battery D-2 was produced in the same manner as the battery D-1, except
 that styrene-butadiene rubber diluted with toluene (toluene:sealant=95:5
 (by weight)) was applied to the gasket 3 as a sealant.
 A battery D-3 was produced in the same manner as the battery D-1, except
 that fluorocarbon resin of which a part of the side chains is substituted
 with a silicon resin, diluted with toluene, was applied to the gasket 3 as
 a sealant and was dried at 160.degree. C. for four hours.
 For comparison, a battery D-4 was produced in the same manner as the
 battery D-1, except that pitch was applied to the gasket 3 as a sealant.
 [Evaluation]
 The batteries thus obtained D-1 to D-4 were caused to pass the high
 frequency heating Reflow furnace in the same manner as the Experiment 1 to
 perform a high temperature environment resistance test.
 In this experiment, however, 50 batteries per each battery D-1 to D-4 were
 observed beforehand to confirm that they had no leakage, then were caused
 to pass the Reflow furnace to examine occurrence of the leakage. The
 batteries which had no leakage then were again caused to pass the furnace
 to examine the occurrence. Table 8 lists the results.
 TABLE 8
 Leakage occurrence ratio after
 Passage of the Reflow furnace
 (%)
 First Second
 Battery Kind of sealant passage Passage
 D-1 Isobutylene-isoprene rubber 0 6
 (Mooney viscosity 40
 Unsaturation ratio 3 mol %)
 D-2 Styrene-butadiene rubber 0 2
 (Mooney viscosity 50
 Unsaturation ratio 15 mol %
 Styrene:Butadiene = 25:75 (by
 weight)
 D-3 VDF of fluorocarbon resin 2 4
 of which a part of the
 side chains is substituted
 with a silicone resin
 D-4 Pitch 100 --
 According to Table 8, the batteries in accordance with the present
 invention have an excellent leakage resistance after the passage of the
 Reflow furnace compared to the battery D-4 using pitch as a sealant. From
 the above, this test has given a result that any of the batteries D-1, D-2
 and D-3 of the present invention hardly caused leakage and thus has an
 excellent leakage resistance after the passage of the Reflow furnace. This
 is because isobutylene-isoprene rubber, styrene-butadiene rubber and
 fluorocarbon resin of which a part of the side chains is substituted with
 a silicon resin, which were used for the sealant, had thermal resistance
 so that thermosoftening was not caused.
 In this experiment, sulfolane was used as the solvent of the organic
 electrolyte, however, the similar effects can also be obtained if 3-methyl
 sulfolane or Tetraglyme is used.
 INDUSTRIAL APPLICABILITY
 The present invention can provide an organic electrolyte battery having an
 excellent discharge performance in a low temperature environment and a
 superior reliability during long term storage, as well as a high
 temperature resistance which enables the battery to be mounted onto a
 substrate according to the Reflow method.
 Furthermore, the present invention also has an effect of simplifying the
 manufacturing process of small-sized portable appliances for which the
 battery of this kind are used, because the invention enables the mounting
 of the battery onto a substrate by the automatic soldering.