Fast Phase Transformation Enabled by Cu Single Atom Stabilized 1T-Rich MoS2 for Efficient Magnesium Ion Storage

Rechargeable magnesium batteries (RMBs) have drawn tremendous attention for large-scale energy storage systems due to their low cost and high safety. However, the high charge density and the slow diffusion of Mg²⁺ in the cathode material limit the development of practical Mg cathode materials. Molybdenum disulfide (MoS₂) is considered as an attractive electrode material for RMBs owing to its layered structure and high theoretical capacity. Unfortunately, its limited intercalation sites and slow phase transitions between 2H and 1T during cycling will lead to low capacity and poor rate capability. Herein, a Cu single atom doped MoS₂ (SACu-MoS₂) is designed for the first time to address the above challenges. The Cu single atom in MoS₂ strengthens the interaction between Mg²⁺ and MoS₂ and promotes electron transfer, thereby achieving excellent rate capability. The enhancing effect of Cu single atom facilitates the reversible conversion between 2H and 1T. As a result, the obtained SACu-MoS₂ exhibits a high specific capacity (up to 375 mAh g⁻¹ at 20 mA g⁻¹), excellent rate capability (122 mAh g⁻¹ at 1000 mA g⁻¹) and outstanding cycling performance (up to 109 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). This work provides decisive guidance for a feasible technical solution and analyses the deep mechanisms on tuning of metal sulfide electrodes for advanced RMBs.