Improve the Capacity of MoS2 for Aqueous Zinc Ion Batteries by Regulating the Electron Spin States of Mo via Se Doping

Molybdenum disulfide (MoS2) is now being considered a feasible cathode candidate for aqueous zinc ion batteries (AZIBs) because of its two-dimensional layered structure that facilitates ion intercalation/deintercalation at edge sites. However, the inherent poor electron conductivity and sluggish kinetics of zinc ions diffusion severely restricts its development and applicability. In this work, we develop a selenium (Se)-doped MoS2 cathode material for AZIBs with a high capacity and long cycle stability. The doped Se alters the electron spin states of the Mo atoms, enhancing their reactivity during intercalation and reducing the diffusion barrier for Zn2+. As a result, synthesized Se-doped MoS2 (MoS2–Se) has a high capacity of 151 mAh g–1 at 1 A g–1, which is superior to the capacity of the original MoS2 (109 mAh g–1 at 1 A g–1). Encouragingly, MoS2–Se also achieved a satisfactory rate performance (45% capacity retention at 10 A g–1) and cycle life (93% of its initial capacity over approximately 500 cycles at 4 A g–1). Furthermore, the fabricated MoS2–Se//Zn battery exhibits a peak energy density of 77 Wh kg–1 and a power density of 0.41 kW kg–1. This work introduces a new design of MoS2 with a substantial capacity, deepening the comprehension of cathodes for AZIBs.