Synthesis of ZnFe₂O₄ Nanospheres with Tunable Morphology for Lithium Storage

ZnFe₂O₄ (ZFO) nanospheres with complex structures have been synthesized by a one-step simple solvothermal method using two different types of precursors-metal chlorides and nitrates -and were fully characterized by XRD, SEM, XPS, and EDS. The ZFO nanospheres synthesized from chloride salts (ZFO_C) were loose with a size range of 100-200 nm, while the ZFO nanospheres synthesized from nitrate salts (ZFO_N) were dense with a size range of 300-500 nm but consisted of smaller nanoplates. The different morphologies may be caused by the different hydrolysis rates and different stabilizing effects of chloride and nitrate ions interacting with the facets of forming nanoparticles. Electrochemical tests of nitrate-based ZFO nanospheres as anode materials for lithium-ion batteries demonstrated their higher cyclic stability. The ZFO_C and ZFO_N samples have initial specific discharge/charge capacities of 1354/1020 and 1357/954 mAh∙g^-1, respectively, with coulombic efficiencies of 75% and 71%. By the 100th cycle, ZFO_N has a capacity of 276 mAh∙g^-1, and for ZFO_C, only 210 mAh∙g^-1 remains after 100 cycles.