The invention relates to a bipolar
sodium ion battery and a preparation method thereof, the bipolar
sodium ion battery comprises a plurality of bipolar pole pieces, a diaphragm and an
electrolyte, the plurality of bipolar pole pieces are sequentially stacked, each bipolar
pole piece comprises an
aluminum foil, an insulating strip and an insulating layer, the
aluminum foil is provided with a first surface and a second surface which are oppositely arranged, each of the first surface and the second surface comprises a positive
electrode region, a bending region and a negative
electrode region which are sequentially arranged, the positive
electrode region is coated with a positive electrode
active layer, and the negative electrode region is coated with hard carbon; the positive electrode
active layer comprises a
transition metal oxide, a
Prussian blue material, a polyanion compound or an amorphous material; the aluminum foils can be folded along the bending area, so that the positive electrode region and the negative electrode region are arranged oppositely; the insulating strip is arranged in the bending region; the insulating layer is clamped between the positive
active layer and the hard carbon; a diaphragm is arranged between every two adjacent bipolar pole pieces; and the
electrolyte is used for conducting
electricity for the positive electrode active layer and the hard carbon and comprises
sodium hexafluorophosphate. The bipolar
sodium ion battery is high in
energy density and long in service life.