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Nonaqueous electrolyte secondary batteryRelated Patent Categories: Chemistry: Electrical Current Producing Apparatus, Product, And Process, Current Producing Cell, Elements, Subcombinations And Compositions For Use Therewith And Adjuncts, Include Electrolyte Chemically Specified And Method, Chemically Specified Organic Solvent Containing, Plural Organic Solvents (i.e., Solvent Mixture), One Of The Organic Solvents Contains A Hetero Ring, Oxygen Is Ring Member Of The Hetero RingNonaqueous electrolyte secondary battery description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060240328, Nonaqueous electrolyte secondary battery. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to a nonaqueous electrolyte secondary battery. BRIEF SUMMARY OF THE INVENTION [0002] Recently, a lithium ion secondary battery has been put on the market as a nonaqueous electrolyte secondary battery for portable apparatuses such as portable phones. This battery uses lithium cobalt oxide (e.g., LiCoO.sub.2) as a positive electrode active material, a graphite material or carbonaceous material as a negative electrode active material, an organic solvent having a lithium salt dissolved as a nonaqueous electrolyte, and a porous film as a separator. A nonaqueous solvent having a low viscosity and a low boiling point is used as a solvent of the electrolyte. For example, Japanese Patent Disclosure (Kokai) No. 4-14769 discloses a nonaqueous electrolyte secondary battery comprising an electrolyte including a mixed solvent consisting essentially of propylene carbonate, ethylene carbonate and .gamma.-butyrolactone, the .gamma.-butyrolactone occupying 10 to 50% by volume of the entire solvent mixture. On the other hand, Japanese Patent Disclosure (Kokai) No. 11-97062 discloses a nonaqueous electrolyte secondary battery using a nonaqueous electrolyte prepared by dissolving lithium borofluoride (LiBF.sub.4) in a solvent consisting of 100% by volume of .gamma.-butyrolactone. [0003] It is of high importance nowadays to decrease the thickness of the secondary battery in accordance with decrease in the thickness of the portable apparatus. In order to decrease the thickness of the secondary battery, it is necessary to decrease the thickness of the jacket housing the positive electrode, the negative electrode, the separator, and the nonaqueous electrolyte. However, in the nonaqueous secondary battery provided with a nonaqueous electrolyte including a mixed solvent containing 10 to 50% by volume of .gamma.-butyrolactone, a reaction takes place between the positive electrode and the nonaqueous electrolyte when the secondary battery is stored at such a high temperature as 60.degree. C. or higher. As a result, the nonaqueous electrolyte is decomposed by oxidation to generate a gaseous material. And also, a gas material is likely to be generated from the negative electrode during the initial charging. What should be noted is that, if the thickness of the jacket is decreased, the jacket is swollen by the gas generation so as to be deformed. If the jacket is deformed, an electronic equipment cannot be housed in the battery. Alternatively, malfunction of the electronic equipment tends to be invited. [0004] In the nonaqueous electrolyte secondary battery, it is also important to further improve the large discharge characteristics and the charge-discharge cycle characteristics. [0005] An object of the present invention is to provide a nonaqueous electrolyte secondary battery that permits suppressing the gas generation during storage of the battery under high temperatures so as to prevent a jacket from being swollen and also permits improving the large discharge characteristics and the charge-discharge cycle life. [0006] According to the present invention, there is provided a nonaqueous electrolyte secondary battery, comprising an electrode group including a positive electrode, a negative electrode containing a material for absorbing-desorbing lithium ions, and a separator arranged between the positive electrode and the negative electrode, a nonaqueous electrolyte impregnated in the electrode group and including a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent, and a jacket for housing the electrode group and having a thickness of 0.3 mm or less, wherein the nonaqueous solvent contains .gamma.-butyrolactone in an amount larger than 50% by volume and not larger than 95% by volume based on the total amount of the nonaqueous solvent. [0007] According to the present invention, there is provided a nonaqueous electrolyte secondary battery, comprising an electrode group including a positive electrode, a negative electrode containing a material for absorbing-desorbing lithium ions, and a separator arranged between the positive electrode and the negative electrode, a nonaqueous electrolyte impregnated in the electrode group and including a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent, and a jacket for housing the electrode group, the jacket being made of a sheet having a thickness of 0.5 mm or less including a resin layer, wherein the nonaqueous solvent contains .gamma.-butyrolactone in an amount larger than 50% by volume and not larger than 95% by volume based on the total amount of the nonaqueous solvent. [0008] Further, according to the present invention, there is provided a nonaqueous electrolyte secondary battery, comprising an electrode group including a positive electrode including a collector and a positive electrode layer formed on one or both surfaces of the collector and containing an active material, a negative electrode including a collector and a negative electrode layer formed on one or both surfaces of the collector and containing a material for absorbing-desorbing lithium ions, and a separator arranged between the positive electrode and the negative electrode, a nonaqueous electrolyte impregnated in the electrode group and including a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent, and a jacket for housing the electrode group and having a thickness of 0.3 mm or less, wherein the positive electrode layer has a porosity lower than that of the negative electrode layer, the positive electrode layer has a thickness of 10 to 100 .mu.m, and the nonaqueous solvent contains 40 to 95% by volume of .gamma.-butyrolactone based on the total amount of the nonaqueous solvent. [0009] Further, according to the present invention, there is provided a nonaqueous electrolyte secondary battery, comprising an electrode group including a positive electrode including a collector and a positive electrode layer formed on one or both surfaces of the collector and containing an active material, a negative electrode including a collector and a negative electrode layer formed on one or both surfaces of the collector and containing a material for absorbing-desorbing lithium ions, and a separator arranged between the positive electrode and the negative electrode, a nonaqueous electrolyte impregnated in the electrode group and including a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent, and a jacket for housing the electrode group, the jacket being made of a sheet having a thickness of 0.5 mm or less including a resin layer, wherein the positive electrode layer has a porosity lower than that of the negative electrode layer, the positive electrode layer has a thickness of 10 to 100 .mu.m, and the nonaqueous solvent contains 40 to 95% by volume of .gamma.-butyrolactone based on the total amount of the nonaqueous solvent. [0010] Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING [0011] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. [0012] FIG. 1 is a cross sectional view exemplifying a nonaqueous electrolyte secondary battery according to first embodiment of the present invention; [0013] FIG. 2 is a cross sectional showing in a magnified fashion a portion A shown in FIG. 1; [0014] FIG. 3 schematically shows the boundary regions between the positive electrode and the separator and between the separator and the negative electrode in the secondary battery shown in FIG. 1; [0015] FIG. 4 is a cross sectional view for explaining the thickness of a positive electrode active material layer in a nonaqueous electrolyte secondary battery according to a second embodiment of the present invention; [0016] FIG. 5 is a cross sectional view exemplifying a nonaqueous electrolyte secondary battery according to a second embodiment of the present invention; [0017] FIG. 6 is a cross sectional view showing in a magnified fashion a portion B shown in FIG. 5; and [0018] FIG. 7 schematically shows the boundary regions between the positive electrode and the separator and between the separator and the negative electrode in the secondary battery shown in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION [0019] A nonaqueous electrolyte secondary battery according to a first embodiment of the present invention comprises an electrode group having a positive electrode, a negative electrode for absorbing and desorbing lithium ions, and a separator interposed between the positive electrode and the negative electrode, a nonaqueous electrolyte permeating the electrode group to have the electrode group impregnated with the nonaqueous electrolyte and containing a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent, and a jacket housing the electrode group. The nonaqueous solvent contains .gamma.-butyrolactone in an amount larger than 50% by volume and not larger than 95% by volume based on the total amount of the nonaqueous solvent. [0020] In the secondary battery of the present invention, it is possible for the positive electrode, the negative electrode and the separator not to be formed as an integral structure. However, it is desirable to form an integral structure under the conditions given in item (a) or (b): Continue reading about Nonaqueous electrolyte secondary battery... Full patent description for Nonaqueous electrolyte secondary battery Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Nonaqueous electrolyte secondary battery patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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