Electrochemical behavior of MgO-templated mesoporous carbons in the propylene carbonate solution of sodium hexafluorophosphate

Abstract

MgO-templated mesoporous carbons annealed from 900 to 1,500 °C were examined as active materials for negative electrodes in a propylene carbonate electrolyte containing 1 M sodium hexafluorophosphate. The carbons annealed at 1,000 °C exhibited 180 mAh g−1 at a rate of 0.1 A g−1 in a potential range of 2.00–0.01 V versus Na+/Na. The carbons showed good rate capability as well as cyclability. It is considered that mesopores plays a role of easy diffusion pathway for ions, and also significantly relates to both electric double layer capacitance and faradaic reactions involving Na ions. X-ray diffraction patterns, nuclear magnetic resonance spectra and Raman spectra were discussed for characterization of the carbons. Raman spectra indicated a reversible interaction of reduced Na with carbons. However, Na intercalation in the carbon layers was not confirmed for the carbon annealed at 1,000 °C. This is because the Na intercalation sites in the carbon layers are very few due to the disordered structure caused by the relatively low temperature annealing.