Amorphous MoS₃ Anchored within Hollow Carbon as a Cathode Material for Magnesium-Ion Batteries.

Abstract

Magnesium-ion batteries are considered the next-generation promising large-scale energy storage devices owing to the low-cost and nondendritic features of metallic Mg anode. Nevertheless, such strong electrostatic interaction between bivalent Mg²⁺ and crystalline cathode materials will lead to low capacity and poor diffusion kinetics, which seriously hinders the further development of magnesium-ion batteries. Herein, amorphization and anion-rich strategies are employed to prepare well-designed cathode materials with MoS₃ anchored on hollow carbon nanospheres (a-MoS₃/HCS). The amorphous MoS₃ provides unrestricted 3D diffusion access and effectively boosts the Mg²⁺ diffusion kinetics, while the anion-rich feature of MoS₃ offers rich active sites for Mg²⁺ storage and finally contributes to a high discharge capacity driven by the anionic redox mechanism. Moreover, the effective modification of hollow carbon nanospheres buffers the volumetric changes of MoS₃ and improves the electron transfer efficiency. Owing to the above-mentioned multiple advantages, a-MoS₃/HCS exhibits an ultrahigh discharge capacity (489.2 mAh g^-1 at 50 mA g^-1) and high cyclic performance (200.1 mAh g^-1 at 2 A g^-1 for 300 cycles), distinctly superior to those of crystalline 1T/2H-MoS₂/HCS and 2H-MoS₂/HCS and surpassing almost all of the molybdenum sulfide-based cathodes. Furthermore, the high-performance a-MoS₃/HCS-based pouch cell with the ability to drive various mini-type devices confirms the potential application values. The excellent magnesium storage properties of a-MoS₃/HCS are further verified by the related kinetics analysis, DFT theoretical calculation, and reversible electrochemical reactions. The amorphous and redox-rich tactics of a-MoS₃/HCS provide an innovative pathway to explore high-efficiency cathode materials for various multivalent-ion batteries.