Carbon-Coated MgFeSiO4/Graphene Conductive Network Cathode Enables Ultrahigh-Rate and Long-Cycle-Life Magnesium-Ion Batteries

Rechargeable magnesium ion batteries (RMBs) have garnered intense interest as a promising energy-storage system due to their high safety. However, developing high-performance cathodes with rapid kinetics is a crucial challenge for advanced RMBs. Herein, an in situ-constructed carbon layer and graphene conductive network structure are proposed to modify the MgFeSiO₄ cathode material (denoted as MgFeSiO₄/C@G). As expected, the synthesized MgFeSiO₄/C@G exhibits high magnesium storage capacities (219.6 mAh g^–1 after 250 cycles at 0.5 C), superior high-rate performance (97.5 mAh g^–1 at 50 C), and long-term cycling stability (a specific capacity of 90.88 mAh g^–1 after 5000 cycles at 30 C with ∼85% capacity retention). Remarkably, the outstanding stability, 93.5% capacity retention at 5 C after 1700 cycles at 50 °C, further affirms the high-temperature adaptability and reliability of MgFeSiO₄/C@G. Moreover, the synthesized MgFeSiO₄/C@G has a small volume change (only 0.24%) during magnesium insertion–extraction, which ensures a prolonged cycle life. The stable integration between MgFeSiO₄ and distinctive conductive network architecture shortens the ion diffusion path, promotes electron transfer, enhances Mg²⁺ diffusion kinetics, and achieves excellent structural stability during the cycling.