Rechargeable Na-CO 2 Batteries Starting from Cathode of Na 2 CO 3 and Carbon Nanotubes

Na-CO 2 batteries have attracted significant attentions due to their high energy density and effective utilization of greenhouse gas CO 2 . However, all reported Na-CO 2 batteries employ excessive preloaded metal Na, which will lead to safety issues such as dendrite formation and short circuit. In addition, the charging mechanism of reported Na-CO 2 batteries is not very clear. Here we report the Na-CO 2 batteries, starting from the cathode of cheap Na 2 CO 3 and multiwalled carbon nanotubes (CNTs). Due to the effective electron transfer and high reactivity, the decomposition of Na 2 CO 3 and CNTs could take place under 3.8 V. The charging mechanism of 2Na 2 CO 3 + C → 4Na + 3CO 2 without any side reactions is revealed by in/ex situ techniques such as Raman, gas chromatograph, and optical microscope. Dendrite-free Na can quantitatively deposit on the Super P/Al anode because of large specific surface area and low nucleation barrier of the anode for Na plating. The batteries could deliver an energy density of 183 Wh kg −1 (based on the whole mass of the pouch-type batteries, 4 g) with stable cycling performance. This work reveals that safe rechargeable Na-CO 2 batteries could be constructed by cheap Na 2 CO 3 and multiwalled carbon nanotubes.