Effects of Carbon-Based Electrode Materials for Excess Sodium Metal Anode Engineered Rechargeable Sodium Batteries

Rechargeable sodium batteries (RSBs) suffer from an absence of suitable active anode materials and noncompetitive energy density because the intercalation chemistry used in well-established lithium ion batteries is unsuitable for larger and heavier sodium ion based batteries. Hence, new types of active anode materials with high performance are needed to realize feasible RSBs. This study examined the effects of carbon-based electrode materials on the most promising sodium metal anode with a high theoretical capacity of ∼1150 mA h g-1 through a comparative study of carbon nanotube (CNT) based electrode materials as a platform sample. This study showed that (1) nitrogen and oxygen dual heteroatom-functionalized CNTs lead to high sodium metal storage performances such as a high Coulombic efficiency of >99.9% and low cell-to-cell variations by <0.6% as well as a sharp reduction of sodium metal nucleation overpotential up to ∼5 mV, (2) highly ordered graphitic structures endure a significantly long cycling process of more than 1000 repetitive sodium metal deposition/dissolution cycles with an average Coulombic efficiency of >99.9%, and (3) more importantly, high-performance electrode materials reduce the excessive sodium metal loading needed to back up the loss during the cycling process, leading to high specific energy/power capabilities and long-term cycle life. These results highlight the feasibility of excess sodium metal anode engineered RSBs based on a high-performance carbon-based electrode material.