Abstract: An object of the present invention is to provide a negative electrode active material etc. which have a high capacity density and which can improve cycle characteristics of a sodium secondary battery using a molten salt electrolyte. The negative electrode active material for a sodium secondary battery using a molten salt electrolyte includes tricobalt tetroxide. In the negative electrode active material, the tricobalt tetroxide preferably has an average particle size d50 of 10 ?m or less and a maximum particle size dmax of 30 ?m or less.

Abstract: A heat resistant battery includes a positive electrode including a positive electrode current collector and a positive electrode active material fixed on the positive electrode current collector, wherein the positive electrode active material includes a sodium-containing transition metal compound capable of electrochemically storing and releasing a sodium ion; a negative electrode including a negative electrode current collector and a negative electrode active material fixed on the negative electrode current collector, wherein the negative electrode active material contains at least one selected from the group consisting of a sodium-containing titanium compound and a non-graphitizable carbon, each of the sodium-containing titanium compound and the non-graphitizable carbon capable of storing and releasing a sodium ion at a lower potential than a potential of the sodium-containing transition metal compound; and a sodium ion-conductive electrolyte provided at least between the positive electrode and the negative

Abstract: Provided is a power supply system capable of being used in a well over a long period of time. A power supply system for a well according to the present invention includes a secondary battery having an operating temperature range including a temperature of the inside of a well and supplying power to a device installed in the well; and a charge-discharge mechanism for charging and discharging the secondary battery, and is installed in the well. The secondary battery to be used in the power supply system may be a molten salt battery, and may include a sensor and communication apparatus.

Abstract: The present invention relates to a sodium secondary battery comprising a positive electrode which includes a positive electrode current collector and a positive electrode material, the positive electrode material being carried on the positive electrode current collector, wherein the positive electrode material comprises a positive electrode active material reversibly containing sodium cation; a negative electrode which includes a negative electrode current collector and a negative electrode material, the negative electrode material being carried on the negative electrode current collector, wherein the negative electrode material comprises a negative electrode active material reversibly containing sodium cation; an electrolyte interposed at least between the positive electrode and the negative electrode; and a separator for retaining the electrolyte and separating the positive electrode and the negative electrode from each other; wherein the negative electrode active material is amorphous carbon, and the elect

Abstract: As a molten salt composition lacking a clear melting point and including a molten salt that can be suitably used as an electrolytic solution of a secondary battery, there is provided a molten salt composition including a mixture of two or more kinds of molten salts which can be used as an electrolytic solution of a secondary battery. Particularly, provided is a molten salt composition comprising two kinds of molten salts each having cations with ion diameters different from each other, composition ratio being set to a composition ratio within a range in which the molten salt composition lacks a melting point. Also provided is a secondary battery including the molten salt composition as an electrolytic solution, which can maintains an available state even when the temperature becomes low without rapidly becoming unavailable.

Abstract: A heat resistant battery includes a positive electrode including a positive electrode current collector and a positive electrode active material fixed on the positive electrode current collector, wherein the positive electrode active material includes a sodium-containing transition metal compound capable of electrochemically storing and releasing a sodium ion; a negative electrode including a negative electrode current collector and a negative electrode active material fixed on the negative electrode current collector, wherein the negative electrode active material contains at least one selected from the group consisting of a sodium-containing titanium compound and a non-graphitizable carbon, each of the sodium-containing titanium compound and the non-graphitizable carbon capable of storing and releasing a sodium ion at a lower potential than a potential of the sodium-containing transition metal compound; and a sodium ion-conductive electrolyte provided at least between the positive electrode and the negative

Abstract: A material design of a molten salt battery which is suitable for a temperature range in which the battery is used is shown, and a molten salt battery applicable even under a severe environment where vibrations are given is provided. In the molten salt battery according to the present invention, the operating temperature range of 25° C. to 300° C. is divided into ranges of 25° C. to 120° C., 80° C. to 140° C. and 140° C. to 300° C., and for each temperature range, a material that is a choice is defined for each of an outer package, a binder, an anode active material and a separator as well as an electrolytic solution. Further, the molten salt battery includes a vibration controlling portion for reducing vibrations given to the outer package. As for the electrolytic solution, for example, an electrolytic solution containing an organic cation and FSA as an anion, or NaFSA is suitable for the range of 25° C. to 120° C.

Abstract: Provided is a power supply system capable of being used in a well over a long period of time. A power supply system for a well according to the present invention includes a secondary battery having an operating temperature range including a temperature of the inside of a well and supplying power to a device installed in the well; and a charge-discharge mechanism for charging and discharging the secondary battery, and is installed in the well. The secondary battery to be used in the power supply system may be a molten salt battery, and may include a sensor and communication apparatus.