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

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 Mg 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 MoS anchored on hollow carbon nanospheres (a-MoS/HCS). The amorphous MoS provides unrestricted 3D diffusion access and effectively boosts the Mg diffusion kinetics, while the anion-rich feature of MoS offers rich active sites for Mg 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 MoS and improves the electron transfer efficiency. Owing to the above-mentioned multiple advantages, a-MoS/HCS exhibits an ultrahigh discharge capacity (489.2 mAh g at 50 mA g) and high cyclic performance (200.1 mAh g at 2 A g for 300 cycles), distinctly superior to those of crystalline 1T/2H-MoS/HCS and 2H-MoS/HCS and surpassing almost all of the molybdenum sulfide-based cathodes. Furthermore, the high-performance a-MoS/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-MoS/HCS are further verified by the related kinetics analysis, DFT theoretical calculation, and reversible electrochemical reactions. The amorphous and redox-rich tactics of a-MoS/HCS provide an innovative pathway to explore high-efficiency cathode materials for various multivalent-ion batteries.