| dc.description.abstract | This thesis focuses on sodium secondary batteries, including investigation on graphene-based anodes, ionic liquid electrolytes, SEI chemistry, safety issues, and graphite cathodes. A microplasma-assisted chemical vapor deposition technique is used to produce graphene nanosheets (denoted as MPGNS). The obtained MPGNS has higher crystallinity and less defects, compared to those of conventional reduced graphene oxides. MPGNS is able to deliver a superior Coulombic efficiency of 45%, a high capacity of 250 mA h g－1(@ 0.03 A g－1), and show excellent rate capability (44% @ 5 A g－1). Using NaFSI/PMP-FSI ionic liquids as electrolytes, the electrochemical reversibility of graphene anodes was improved. After formation cycles, the Coulomic efficiency is close to 100%. This study demonstrates a superior SEI film derived by NaFSI/PMP-FSI ionic liquids, which exhibits a better stability against charge-discharge process and elevated temperatue, compared to those of conventional organic electrolytes. In this way, Coulombic efficiency, cyclic stability, and safety are enhanced. Moreover, Na ion fractions considerably impact on SEI chemistry. 2 M NaFSI/PMP-FSI generates the most robust SEI film with the ideal balance between organic and inorganic ingredients, improving the adhesion and electrochemical steadiness. Apart from electrolyte compositions, the surface characteristic also determines the formation and effectiveness of SEI films. Take MPGNS for example, the oxygen-containing functional groups can act as nucleation sites, and thus rapidly passivate charged anodes. Concerning the aspect of safety, this study systematically analyzes the thermal behaviors between charged anodes and electrolytes using DSC. Finally, anion intercalation into graphite cathodes using NaFSI/PMP-FSI as electrolytes shows the high working voltage above 4.5 V (vs. Na/Na+), which promisingly enables high energy density and replacement of rather expensive transition metal-based cathode materials. | en_US |