Reversible hybrid sodium-CO2 batteries with low charging voltage and long-life

A reversible long-life hybrid Na-CO2 battery is proposed by using Na3Zr2Si2PO12 solid electrolyte as a separator, N-doped single-wall carbon nanohorns (N-SWCNH) as a catalyst and the saturated NaCl solution as an aqueous catholyte. The Na3Zr2Si2PO12 ceramic not only has high Na+ ion conductivity, but also prevents potential contamination from H2O and CO2 to sodium anode, and avoids the internal short-circuit touch of Na dendrite with cathode, improving the safety of the battery. Benefiting from N dopants, unique internal and interstitial nanoporous structures, N-SWCNH have large surface area for discharge products accumulation, offer substantial structural defect sites for CO2 adsorption and electron transfer, contributing to high catalytic activity and reversibility. Most importantly, the hybrid Na-CO2 battery with aqueous electrolyte facilitates the dissolution of the insulated discharge product, which overwhelmingly improves the discharge and charge reactions kinetics. Na-CO2 batteries exhibit a low charging voltage of 2.62 V and a small voltage gap of 0.49 V at a current density of 0.1 mA cm(-2), a superior discharge capacity of 2293 mAh.g(-1) at a current density of 0.2 mA cm(-2), a high round trip efficiency of similar to 68.7% after 300 cycles. In-situ Raman and ex-suit XRD analyses convincingly show that NaHCO3 and carbon are the main discharge products.