Abstract: A driving method of a fuel cell system, which includes a secondary battery and a fuel cell stack, is disclosed. The method includes detecting a state of charge (SOC) of the secondary battery, driving the fuel cell stack to an on-state whenever the SOC of the secondary battery is less than a predetermined first SOC, and driving the fuel cell stack to an off-state whenever the SOC of the secondary battery is greater than a predetermined second SOC. In this method, the fuel cell stack is driven at a fuel concentration having optimum efficiency, thereby increasing the fuel efficiency of the fuel cell system.

Abstract: A lithium polymer battery includes a polymer electrolyte or a gel polymer electrolyte having a nonaqueous organic solvent, a lithium salt, an ion-conducting polymer and a fluorinated benzene; a positive electrode; and a negative electrode.