Facile Synthesis of Hierarchical Iron Phosphide/Biomass Carbon Composites for Binder-Free Sodium-Ion Batteries

Seeking a simple direct construction strategy for transition-metal-phosphide-based composites as anodes for sodium-ion batteries is attracting great attention for the development of high-performance sodium-ion batteries. In this work, we design iron phosphide nanosheets grown on a biomass carbon membrane by a facile electrodeposition method, followed by an annealing process. The biomass carbon membranes as three dimensional frameworks, possessing initial biological structures from Magnolia leaves, do not only improve the conductivity of the electrodes but also relieve iron phosphide aggregation during the charging-discharging processes. The iron phosphide nanosheets could increase the accessible surface area for electrochemical reactions, further promoting the storage of sodium ions. Due to the unique structure of the iron phosphide nanosheets/biomass carbon membrane, the electrodes exhibit 500.9 mAh g at a current density of 50 mA g after 100 cycles. Even at a high current density of 500 mA g, the electrodes still retain 197 mAh g after a long-time test (500 cycles). These novel features make the composite a great potential anode material for binder-free sodium-ion batteries.