SECONDARY BATTERY AND USING METHOD THEREOF, AND POWER STORAGE DEVICE

PROBLEM TO BE SOLVED: To provide a secondary battery having high energy density per volume and capable of preventing battery capacity from being rapidly reduced due to deterioration.SOLUTION: A secondary battery includes a first electrode 1, a second electrode 2, and an electrolyte 3. At least one of the first electrode 1 and second electrode 2 is a multiple potential electrode having at least two or more oxidation-reduction potentials associated with insertion and desorption of an alkali metal in a wide range of potential so as not to decompose the electrolyte 3, and a difference in the adjacent oxidation-reduction potentials of the multiple potential electrodes is equal to 0.7 V or less. The secondary battery is used by switching two electric connections of the first electrode 1 and second electrode 2 after discharging, with detection means for detecting a charging end of the secondary battery so as to set both the first electrode 1 and the second electrode 2 to the multiple potential electrodes, and means for switching the electric connections of the first electrode 1 and second electrode 2.