Phosphorous-derived high ionic conductive host towards robust dendrite-free sodium metal anodes

Sodium (Na) metal is one of the most promising anodes for next-generation Na metal batteries due to its high theoretical specific capacity and low potential. Nevertheless, the uncontrollable dendritic Na growth and the hostless nature impede its practical applications. Herein, we report a dendrite-free composite Na metal anode that delivers low potential hysteresis during cycle. The anode is composed of 10 wt% phosphorus-coated carbon black, which can be derived into uniformly distributed sodium phosphide host during repeated mechanical kneading processes. High ionic conductive sodium phosphide greatly promoted the even distribution of Na + flux and its transportation kinetics, thus effectively inhibiting the growth of Na dendrites and improving the cycling stability of the composite anode. Additionally, robust alloy host in anode enhances the mechanical flexibility and relieve the issue of poor processability owing to sticky property of metallic Na. As a result, the symmetric cells using thin composite electrode exhibits long-term cycling with low potential hysteresis (21 mV at 1 mA cm −2 and 80 mV at 3 mA cm −2 ). Impressively, a full cell paired with Na 3 V 2 (PO 4 ) 3 cathode shows a high capacity-retention of 90.7 % for 1000 cycles at 0.5 C .