Fabrication of Bi nanospheres assembled microspheres with petal structure || B, N-co-doped C nanosheets hybrid sodium-ion capacitors with ultrahigh power density, high energy density and long cycle life

Abstract

To develop high-performance hybrid sodium-ion capacitors, B, N co-doped C nanosheets and Bi nanospheres assembled microspheres with petal structure (labelled as Bi NAMPS) are synthesized, which are used as the cathode and the anode, respectively. In sodium-ion half cells, the B, N co-doped C nanosheets show pseudocapacitive behavior, with a stable capacity of 108 mAh g −1 at 0.1 A g −1 , superior rate capability (72.9 mAh g −1 at 20 A g −1 ) and capacity retention of ∼100% after 15000 cycles at 5 A g −1 . The Bi NAMPS present battery-type characteristics, with a first reversible capacity of 365 mAh g −1 at 0.2 A g −1 , excellent rate capability (343, 338 and 304 mAh g −1 at 10, 20 and 40 A g −1 , respectively) and capacity retention of 91% after 7000 cycles at 10 A g −1 . Hybrid sodium-ion capacitor constructed by pairing them exhibits an ultrahigh power density of 33 kW kg −1 (total) , a high energy density of ∼93 Wh kg −1 (total) and a long cycle life of 5000 cycles. The improved electrochemical performance of the hybrid sodium-ion capacitor is ascribed to the excellent electrochemical behaviors of the anode and cathode. • Improve the cycle life of the Bi anode and the capacity of the carbon cathode. • Fabricate novel Bi NAMPS.||B, N-co-doped C nanosheets hybrid sodium-on capacitors • Achieve ultrahigh power density and excellent cycle life of sodium-ion capacitors.