Bismuth selenide nanocrystalline array electrodes for high-performance sodium-ion batteries

This work, for the first time, reports on the Bi2Se3 nanocrystal array wrapped by amorphous carbon layer as anode for high-performance sodium-ion batteries. In addition to a remarkable lithium storage capability, the Bi2Se3 nanocrystal array assembling onto flexible carbon cloth exhibits an outstanding cyclical stability for sodium ion batteries, which delivers a discharge capacity of 652.1 mAh g−1 at 100 mA g−1 (∼ a rate of 0.1 C) after 100 cycles. Even at 1 A g−1, a reversible capacity of 210.2 mAh g−1 can be maintained undergoing 200 charge-discharge cycles. The excellent cycle and rate capabilities of Bi2Se3 nanocrystal array could be attributed to the stable structure, fast ion migration channel and low charge transfer resistance for electrochemical processes. Detailed investigation reveals the appreciated reversibility of stepwise conversion and alloying reaction of Bi2Se3 nanocrystal array with high Coulombic efficiency and reversible capacity.