Rational design and regulation of tremella-like selenium-doped MoS2 for highly reversible sodium storage

Abstract

Molybdenum disulfide (MoS₂), due to its high theoretical specific capacity (670 mA h g⁻¹), has evoked considerable investigation interest in the area of Na⁺ storage. Nonetheless, the irreversible conversion of the original material MoS₂ into Mo/Na₂S during sodium insertion incurs rapid capacity degradation. Herein, to avoid this severe irreversibility, Na_yMoS₂ is employed to replace the above irreversible products to facilitate subsequent sodium extraction, achieving reversible transformation of the raw material. In order to accomplish this goal, tremella-like hollow MoS_2(1−x)Se_2x@C (x = 0, 0.1, 0.25, 0.5) spheres are elaborately prepared and then act as an appropriate anode material exhibiting good sodium storage capacity. It is proved that doping with Se and regulating the cut-off voltage improve the layer spacing and bond strength, so that the Mo–S bond is maintained without irreversible change during the sodium storage process. This work delivers a practical strategy to modify the energy storage ability via reversible transformation of the original material and proposes an appropriate Se doping amount, demonstrating effective measures for constructing a relevant advanced anode.