Synthesis of Zn2SnO4 anode material by using supercritical water in a batch reactor

Zn2SnO4 anode powders were successfully synthesized using supercritical water (SCW) and metal salt solutions with 10 min reaction time. Effect of NaOH concentration, Zn to Sn ratio, and synthesis temperature were studied with a SCW batch reactor. X-ray diffraction (XRD), scanning electron microscopy (SEM), and charge/discharge cycling tests were employed to characterize the physical properties and electrochemical performance of the as-prepared samples. Alkaline solution concentration and synthesis temperature played a key role in the production of single-phase Zn2SnO4 powders. At a solution concentration of 0.3 M NaOH and a molar ratio of Zn:Sn = 2:1 at 400 °C and 30 MPa, the average size range of the pure Zn2SnO4 powders was 0.5–1.0 μm, and the morphology was nearly uniform and cubic-like in shape. The initial specific discharge capacity of the Zn2SnO4 powders prepared at this condition was 1526 mAh/g at a current density of 0.75 mA/cm2 in 0.05–3.0 V, and their irreversible capacity loss was 433 mAh/g. The discharge capacities of the Zn2SnO4 powders decreased with cycling and remained at 856 mAh/g after 50 cycles, which was 56% of the initial capacity.