Long-life sodium–sulfur batteries enabled by super-sodiophilic seeds†

Abstract

Sodium–metal batteries (SMBs) are an appealing sustainable low-cost alternative to lithium–metal batteries due to their high theoretical capacity (1165 mA h g⁻¹) and abundance of sodium. However, the practical viability of SMBs is challenged by a non-uniform deposition and uncontrollable growth of dendrites at the Na–metal anode. We employ here a super-sodiophilic BiF₃ as a pre-planted seed to guide a uniform Na nucleation and deposition along the current collector. With the assistance of BiF₃, Na metal infiltrates easily into a carbon nanotube (CNT) paper matrix within a second. Such a Na anode exhibits a superior cycle life of >2000 h with an extremely low overpotential of only 13.5 mV and a high coulombic efficiency of 99%. A full cell assembled with this anode and a sulfur cathode with a low negative to positive electrode capacity (N/P) ratio of ∼2 exhibits good cycling stability over 700 cycles. This work demonstrates a promising approach for the development of sustainable, low-cost SMBs.