Flame Spray Pyrolysis for Finding Multicomponent Nanomaterials with Superior Electrochemical Properties in the CoO x ‐FeO x System for Use in Lithium‐Ion Batteries

High‐temperature flame spray pyrolysis is employed for finding highly efficient nanomaterials for use in lithium‐ion batteries. CoO x ‐FeO x nanopowders with various compositions are prepared by one‐pot high‐temperature flame spray pyrolysis. The Co and Fe components are uniformly distributed over the CoO x ‐FeO x composite powders, irrespective of the Co/Fe mole ratio. The Co‐rich CoO x ‐FeO x composite powders with Co/Fe mole ratios of 3:1 and 2:1 have mixed crystal structures with CoFe 2 O 4 and Co 3 O 4 phases. However, Co‐substituted magnetite composite powders prepared from spray solutions with Co and Fe components in mole ratios of 1:3, 1:2, and 1:1 have a single phase. Multicomponent CoO x ‐FeO x powders with a Co/Fe mole ratio of 2:1 and a mixed crystal structure with Co 3 O 4 and CoFe 2 O 4 phases show high initial capacities and good cycling performance. The stable reversible discharge capacities of the composite powders with a Co/Fe mole ratio of 2:1 decrease from 1165 to 820 mA h g −1 as the current density is increased from 500 to 5000 mA g −1 ; however, the discharge capacity again increases to 1310 mA h g −1 as the current density is restored to 500 mA g −1 .