MOF-derived Al-doped Na2FePO4F/mesoporous carbon nanonetwork composites as high-performance cathode material for sodium-ion batteries

An Al-doped Na 2 FePO 4 F/mesoporous carbon nanonetwork derived from an metal–organic framework (MOF) material, was synthesized using a simple solid-state reaction method and evaluated as a promising cathode material for sodium-ion batteries. The MIL-53(Al) derived mesoporous carbon nanonetwork coating can enhance electron conductivity in Na 2 FePO 4 F cathode materials. The doping derived from MIL-53(Al) caused no damage to the crystal structure of the material, and Fe 2+ site was replaced by Al 3+ successfully. Therefore, the Al-doped Na 2 FePO 4 F/MOF-C composites exhibit substantial improvements in electrochemical performance in terms of rate capability and cycle performance. When current density increased from 0.1 C to 5 C, the specific capacity of Na 1.94 Fe 0.94 Al 0.06 PO 4 F/MOF-C only decreased from 115.2 mAh g −1 to 63.2 mAh g −1 ; thus, the composite presented outstanding rate capability. Moreover, an excellent capacity retention of 70.3% was maintained from the initial value of 70.4 mAh g −1 to 49.5 mAh g −1 after the 500th cycle at 5 C. This study provides insights into designing high-performance cathode materials by improving structural stability and the electrical conductivity induced by MOF-derived carbon coating and metal doping.