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 CoFe₂O₄ and Co₃O₄ 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 Co₃O₄ and CoFe₂O₄ 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 mAhg^-1 as the current density is increased from 500 to 5000 mAg^-1; however, the discharge capacity again increases to 1310 mAhg^-1 as the current density is restored to 500 mAg^-1.