Electrochemical evaluation of porous CaFe(2)O(4) anode material prepared via solution combustion synthesis at increasing fuel-to-oxidizer ratios and calcination temperatures

The drawbacks of common anodes in lithium-ion batteries (LIBs) and hybrid supercapacitors (HSCs), such as the high voltage plateau of Li(4)Ti(5)O(12) (1.55 V vs. Li/Li(+)) and the moderate capacity of graphite (372 mAh-g(-1)), have established a need for better materials. Conversion materials, and in particular iron oxide and CaFe(2)O(4) (CFO), have amassed recent attention as potential anode replacements. In this study, we evaluate the material and electrochemical effects of the solution combustion synthesis (SCS) of porous CFO across novel fuel-to-oxidizer ratios and calcination temperatures. We demonstrate that nearly doubling the amount of fuel used during synthesis increases capacities between 120 and 150% at high current densities (~ 1000 mA-g(-1)) and across 500 additional charging-discharging cycles, an effect brought on in part by enhanced compositional purity in these samples. However, in order to ensure long-term cyclic stability, it is necessary to also calcine porous CFO to 900 °C to enhance crystallite size, particle size and spacing, and compositional purity.