Electrochemical performances of Na2MnSiO4 as an energy storage material in sodium-ion capacitors

Abstract

In this work, we report the synthesis of Na2MnSiO4 via high-temperature solid-state chemical reaction method. The crystal structure and morphology of the synthesized Na2MnSiO4 material prepared at different temperatures (600, 700, 800, and 900 °C) were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy. The XRD patterns indicate that high-purity Na2MnSiO4 was obtained at the annealing temperature above 700 °C. The morphology observed by SEM shows that the particle size of the material increased with the increase of annealing temperature. Electrochemical energy storage performance of the material measured by galvanostatic charge–discharge reveals that the material prepared at 800 °C demonstrated the best energy storage capability with a specific capacitance of 123.8 F g− 1 at 0.5 Ag− 1. In addition, the material shows relatively good stability and 82% of initial capacitance was retained after 1000 charge–discharge cycles. Further testing by electrochemical impedance spectroscopy shows that the synthesized Na2MnSiO4 electrode has low series resistance (1.3 Ω) and charge transfer resistance (7.4 Ω), favoring the delivery of electrical power at a fast rate. These results suggest that the synthesized Na2MnSiO4 material has great potential for application in sodium-ion capacitors.