NaF-rich interphase and high initial coulombic efficiency of red phosphorus anode for sodium-ion batteries by chemical presodiation

Red phosphorus/carbon (P/C) materials have been extensively studied as promising anodes for sodium-ion batteries (SIBs) owing to their high capacities and moderate working potentials. However, the low initial Coulombic efficiency (ICE) and unstable solid-electrolyte interphase (SEI) of P/C composites limit their widespread applications. In this study, we develop an effective presodiation method to compensate for the irreversible sodium loss of the S-doped P/C (P/C@S) anode and yield a thin, uniform, and NaF-rich SEI layer on the presodiated P/C@S (pNa-P/C@S) anode during cycling. Consequently, the pNa-P/C@S anode exhibits a remarkable ICE of 98.7% as well as superior cycling performance and rate capability in the half cell. When pNa-P/C@S anode is coupled with conventional Na3V2(PO4)2F3, Na3V2(PO4)3, and NaCu0.12Ni0.23Fe0.33Mn0.33 cathodes, all the full cells demonstrate desirable ICEs (>98%), high energy densities, and excellent cycling performance. The proposed method has been extended to another anode (SnO2) to demonstrate its applicability in fabricating anodes with a high ICE and stable NaF-rich SEI layer.