Large-scale production of spherical FeSe₂-amorphous carbon composite powders as anode materials for sodium-ion batteries

A simple two-step method involving a large-scale spray drying process is developed to synthesize metal selenide-amorphous carbon (AC) composite powders (on a kilogram scale) for use as anodes in sodium-ion batteries. The composite powders of iron salt, dextrin, and H₂SeO₃ are generated in a spray drying process to form the FeSe₂-AC composite powders by a one-pot post-treatment process under a reducing atmosphere. The ultrafine FeSe₂ single crystals with sizes below 20 nm are uniformly dispersed within the amorphous carbon in the FeSe₂-AC composite powders prepared from the spray solution with 30 g L^− 1 dextrin. The discharge capacities of the powders prepared from spray solutions with 0, 10, 20, and 30 g L^− 1 dextrin for the 150th cycle at a current density of 0.5 A g^− 1 are 85, 194, 203, 379 mA h g^− 1, respectively; their corresponding capacity retentions measured from the second cycle are 19%, 40%, 46%, and 99%. The spherical shape of the FeSe₂-AC composite powders is maintained even after 100 cycles. The FeSe₂-AC composite powders maintain a high structural stability during repeated sodium insertion and desertion processes, and show superior cycling and rate performances compared to those of the bare FeSe₂ powders.