Facile synthesis and electrochemical Mg-storage performance of Sb2Se3 nanowires and Bi2Se3 nanosheets

Abstract

Rechargeable Mg batteries are considered as low-cost and reliable candidates for efficient energy storage, but their development is blocked by the lack of suitable cathode materials. In this work, Sb₂Se₃ nanowires and Bi₂Se₃ nanosheets are fabricated by facile one-step hydrothermal methods and their Mg-storage performances are systematically investigated. The results show that the Bi₂Se₃ nanosheets with stable hierarchical 2D structure exhibit a better performance. Because of its thin nanosheet structure, Bi₂Se₃ provides a high Mg-storage capacity of 144 mA h g⁻¹ and a remarkable rate capability with 65 mA h g⁻¹ delivered at 1000 mA g⁻¹. Bi₂Se₃ also exhibits an outstanding cyclability over 350 cycles owing to its hierarchical structure. Furthermore, this study reveals that the electrochemical charge/discharge cycling is a typical conversion reaction occurring between Bi³⁺ and metallic Bi⁰. Kinetic investigation suggests that the high performance of Bi₂Se₃ is attributed to both its intrinsic nature and its thin nanosheet structure facilitating solid-state Mg²⁺ diffusion. The present work highlights the selection principle of conversion cathodes for rechargeable Mg batteries, namely matching a soft anion with a quasi-soft metal cation. Moreover, the facile synthesis approach is also used for low-dimensional main-group VI metal chalcogenides to improve the Mg-storage performance.