Interlayer-expanded MoS₂ nanoflowers anchored on the graphene: A high-performance Li⁺/Mg²⁺ co-intercalation cathode material

Li⁺/Mg²⁺ hybrid-ion batteries (LMIBs), integrating the merits of lithium ion batteries (LIBs) and magnesium ion batteries (MIBs) are considered as an attractive alternative of next generation metal secondary batteries. Due to the sluggish solid-state diffusion kinetic induced by the strong Coulombic interaction between Mg²⁺ and host materials, pristine MoS₂ with interplanar distance of 0.62 nm exhibits inferior electrochemical performance for LMIBs with only Li⁺ intercalation. Herein, we report an oxygen-incorporated MoS₂ (O-MoS₂) nanoflower anchored on graphene (O-MoS₂/G) with the interplanar distance of O-MoS₂ from 0.62 nm expanded to 0.885 nm. Even at 1000 mA g⁻¹, the expanded interlayer spacing can still ensure the Mg²⁺ and Li⁺ intercalation/deintercalation into/from the host material simultaneously. Meanwhile, this configuration can effectively reduce the diffusion barrier of metal ions, increase the intercalated number of ions, and enhance the stability of structure. In addition, we found and demonstrated the intercalated Li⁺ had a boosting effect to the intercalation kinetics of Mg²⁺. Compared with the MIBs, the migration energy barriers of Mg²⁺ under the existence of Li⁺ intercalating into MoS₂ is reduced from 0.36 eV to 0.16 eV, meanwhile the corresponding intercalation capacity and diffusion coefficient of Mg²⁺ are 1.38 and 7.1 times as large as MIBs. As expect, the O-MoS₂/G exhibits superior rate capability and cycling performance with a reversible capacity of 123.3 mAh g⁻¹ after 2000 cycles charge–discharge processes at 1000 mA g⁻¹.