The invention relates to a
sodium ion capacitor with a negative pole made of a FeS2-xSex material. The
sodium ion capacitor comprises a positive pole sheet, a negative pole sheet, a diaphragm, an
electrolyte and a shell; an active material, a conductive agent and a binder are mixed, a
solvent is added into an obtained mixture, the
solvent and the mixture are mixed to form a
slurry, the
slurry coats a collector, and therefore, the negative pole sheet can be obtained; and the active material in the negative pole sheet of the
capacitor is the FeS2-xSex material, wherein x ranges from 0.1 to 1. The negative pole of the
sodium ion capacitor of the invention is made of the FeS2-xSex material; the peak position of the XRD
diffraction pattern of the FeS2-xSex material slightly shifts leftwards compared with that of FeS2, which indicates that an inter-layer spacing is increased, and therefore, the implanting and extraction of sodium ions can be better facilitated; the
diffusion of Na<+> is faster,
electronic conductivity is higher, and therefore, the high-current
charge and discharge capacity of the sodium ion capacitor can be greatly improved, namely, the
power performance of the sodium ion capacitor is improved; if the
power density of the sodium ion capacitor is 172 W kg<-1>, the
energy density of the sodium ion capacitor is as high as 67 Wh kg<-1>; and even if the
power density of the sodium ion capacitor is as high as 2543 W kg<-1>, the
energy density of the sodium ion capacitor is still maintained at about 27Wh kg<-1>.