Ultrasonic sonochemical synthesis of Na0.44MnO2 insertion material for sodium-ion batteries

The energy-demanding nature of solid-state synthesis can be circumvented by using solvothermal synthesis routes involving milder heat treatment steps. Herein, we exploit one such route, ultrasonic sonochemical method, for the synthesis of Na0.44MnO2 insertion material. Using simple oxide and carbonate precursors, the target compound can be successfully prepared by restricting the final annealing (at 900 °C) to within 2 h. Rietveld analysis confirms the purity of final product assuming an orthorhombic framework (s.g. Pbam). Involving a step-wise voltage profile with the average Mn4+/Mn3+ redox potential ∼3 V (vs. Na/Na+), it delivers reversible capacity over 110 mAh.g−1 at a rate of C/10 with decent rate kinetics and cycling stability. Ultrasonic sonochemical synthesis can be employed for synthesis and rapid screening of variety of insertion materials for sodium-ion batteries.