One-Pot Synthesis of CoSex-rGO Composite Powders by Spray Pyrolysis and Their Application as Anode Material for Sodium-Ion Batteries

A simple one‐pot synthesis of metal selenide/reduced graphene oxide (rGO) composite powders for application as anode materials in sodium‐ion batteries was developed. The detailed mechanism of formation of the CoSex–rGO composite powders that were selected as the first target material in the spray pyrolysis process was studied. The crumple‐structured CoSex–rGO composite powders prepared by spray pyrolysis at 800 °C had a crystal structure consisting mainly of Co0.85Se with a minor phase of CoSe2. The bare CoSex powders prepared for comparison had a spherical shape and hollow structure. The discharge capacities of the CoSex–rGO composite and bare CoSex powders in the 50th cycle at a constant current density of 0.3 A g−1 were 420 and 215 mA h g−1, respectively, and their capacity retentions measured from the second cycle were 80 and 46 %, respectively. The high structural stability of the CoSex–rGO composite powders for repeated sodium‐ion charge and discharge processes resulted in superior sodium‐ion storage properties compared to those of the bare CoSex powders. Spray composites: A simple one‐pot synthesis of metal selenide/reduced graphene oxide (rGO) composite powders by a spray pyrolysis process was developed (see figure). This process could be applied in the preparation of crumple‐structured cobalt selenide/rGO composite powders with various compositions for applications including anode materials for sodium‐ion batteries.