Sodium-Ion Battery

A sodium ion battery includes an anode sheet, a cathode sheet, a separating film disposed between the cathode sheet and the anode sheet, and an electrolyte including a non-aqueous organic solvent anda sodium salt dissolved in the non-aqueous organic solvent. The electrolyte further comprises an additive dissolved in a non-aqueous organic solvent, the additive having a charge/radius ratio of cations smaller than that of sodium ions. The cathode active material in the cathode sheet includes a Prussian blue-based material. The charge/radius ratio of the cation of the electrolyte additive of thepresent invention is smaller than the charge/radius ratio of the sodium ion, During the charge and discharge process of sodium ion battery, the cation is preferentially inserted into the Prussian bluematerial, and the structure of the Prussian blue material is less damaged in the process of insertion and removal, so that the three-dimensional framework structure of the Prussian blue material canbe stabilized, and the sodium ion battery has good cycle performance.