Tailored thickness engineering of Bi2Se3 nanosheets for superior cathodic performance in aqueous zinc-ion batteries

Abstract

Bi2Se3 is considered a suitable cathode material for zinc-ion batteries (ZIBs) because of its high conductivity and large layer spacing. Herein, Bi2Se3 nanosheets with varying thicknesses are successfully synthesized using a one-step solvothermal process with adding different amounts of ethylenediamine. The introduction of ethylenediamine reduces the thickness of Bi2Se3 from 250 nm to 22.7 nm. The thin structure exposes more active sites and shortens ion transport paths. Therefore, the optimized Bi2Se3 nanosheet exhibits outstanding specific capacity (410 mA h g−1 at 0.2 A/g), high-rate performance (230 mA h g−1 at 5 A/g), and remarkable cycling stability (82.3 % capacity retention after 1200 cycles at 5 A/g). Furthermore, an in-depth exploration of cathodes during cycling is conducted to investigate the charge/discharge mechanism. A dynamic phase transition from Bi2Se3 to BiSe, accompanied by nanosheet exfoliation, is observed during the initial few cycles, designating BiSe as the primary active material. Moreover, an additional redox reaction involving multiple electrons has been proposed. This study offers a valuable guidance for utilizing Bi2Se3 as a cathode in ZIBs.